A viscosity grade describes how an oil flows, cold and hot, and that is the entire job it does. SAE J300, the standard behind a grade like 20W-50, says exactly that in its own scope. The grade tells you nothing about whether an oil suits a wet clutch, nothing about additive chemistry, and nothing about whether it will protect your engine. That one fact settles most of the arguments people have about grades. What follows is where the grade comes from, what its two halves are measured against, and what the motorcycle market actually files, using data anybody can download for nothing. Before you touch anything The grade is your maker’s call and not a rule you can derive. SAE classifies engine oils in rheological terms only. Nothing on this page lets you work out which grade your engine wants, and your owner’s manual is the only thing that does. A grade tells you nothing about clutch friction. Two oils sharing a grade can behave differently against a wet clutch, so matching the numbers on the front of a bottle covers only half of what a machine with a shared sump needs. We do not print the grade limits table, and free sources cannot either. SAE sells J300 rather than publishing it, so a page telling you the temperature at which a given grade stops pumping is not working from the free material. Substituting a grade because the right one is out of stock is a decision, not a formality. Where a maker ties a grade to an ambient range, that range is part of the requirement and not a suggestion attached to it. If you are pouring it in today as well as choosing it, the hot oil, hot exhaust, fire and used oil handling hazards belong to that job. They are set out, with the EPA guidance on used oil, on our motorcycle oil change guide. What SAE J300 is, and what its scope says The standard is SAE J300, Engine Oil Viscosity Classification. The current revision is J300_202405, revised 9 May 2024, issued by the SAE Fuels and Lubricants TC 1 Engine Lubrication committee. SAE's own record gives the original issue as June 1911, which makes this one of the older standards still in daily use. SAE publishes the title, scope, committee and revision history free, and sells the document itself. So the scope can be quoted, and here it is exactly: "This SAE Standard defines the limits for a classification of engine lubricating oils in rheological terms only. Other oil characteristics are not considered or included." That is from SAE's record for J300_202405. Read that twice. Rheological means flow. The phrase about other oil characteristics not being considered or included is the standard telling you, in its own scope, that a grade on a bottle is a statement about flow behaviour and about nothing else. What the two numbers actually denote The grade limits table is behind SAE's paywall, so we do not reproduce it, and a page that prints those limits without saying where it got them owes you an explanation. What can be described is the structure, because API 1509 is free and sets it out directly in Annex F. API describes two series of grades, those containing the letter W and those that do not. A W grade is defined by maximum low-temperature cranking and pumping viscosities together with a minimum kinematic viscosity measured hot. A grade without the W is defined by a band of kinematic viscosity measured hot, plus a minimum high-temperature high-shear viscosity measured hotter still and under high shear. So in a grade written 20W-50, the 20W part is the cold half, set by how the oil behaves when you crank a cold engine and when the pump has to pull it through. The 50 part is the hot half, set by how thick it remains at operating temperature and how it holds up under shear. A multigrade has to satisfy all of that at once: the cold cranking and pumping limits, a hot kinematic viscosity inside the band of one of the non-W grades, and the high-temperature high-shear minimum. Two numbers, two ends of a temperature range. Nothing in either half is a measure of protection, detergency or friction behaviour. What the grade does not tell you This matters more on a motorcycle than on a car, because the friction question belongs to a different standard entirely. Whether an oil suits a clutch running in the engine oil is answered by a JASO class, which we go through in JASO MA, MA2 and MB, what the classes actually mean. The grade and the class sit on the same bottle and answer different questions, and satisfying one does not get you the other. API puts the purpose of grades the same way. It states that SAE viscosity grades constitute a classification for engine lubricating oils "in rheological terms only and are intended for use by engine manufacturers in determining the engine oil viscosity grades to be recommended for use in their engines and by oil marketers in formulating and labeling their products." A grade is a shared language between the manufacturer who specifies and the blender who labels. It is not advice to a rider. Which grades exist API publishes which grades are eligible for its own marks, in API 1509 Table A-2. That list runs 0W, 5W, 10W, 15W, 20W and 25W on the W side, and 16, 20, 30, 40, 50 and 60 on the high-temperature side. That is API's eligibility list rather than the SAE grade table, and we present it as exactly that. What the motorcycle market actually files Here is something you can check for nothing and that nobody else seems to publish. The JASO Engine Oil Standards Implementation Panel keeps a free register of every oil holding a current four-stroke filing, and it lists the viscosity grade of each one. The edition we parsed is dated 1 September 2026 and holds 2,627 entries. Counting the grades gives a picture of what motorcycle oil actually is on the public record. Viscosity grade Filings in the register 10W-40 862 10W-30 492 20W-50 345 15W-50 202 20W-40 174 10W-50 174 5W-40 160 5W-30 57 Below those come 15W-40 with 44 filings, 10W-60 with 43, 5W-50 with 21 and 0W-30 with 17, and then a long tail present in small numbers: 25W-60, 0W-40, 25W-50, 15W-60, 20W-60 and 0W-50. Two things are worth drawing out. 10W-40 on its own accounts for more filings than the next two grades put together, and the thinnest grades that fill a supermarket shelf are barely present here at all. That is a description of a filing register and not a recommendation. Your machine's grade is whatever its maker specifies for your climate, and no distribution table overrides that. Does the W stand for winter? It is the most repeated claim about a grade, and we could not verify it. Nothing in SAE's free record for J300, and nothing in API 1509, states what the letter W abbreviates. Winter is asserted almost everywhere, but not by any primary source we could find, so we are not going to print it as a fact. What can be said is what the W marks, which is the half of the grade defined by cold-temperature limits. The one thing it certainly does not mean is weight. A related caution: any temperature at which a specific grade will or will not pump comes out of the paywalled limits table, so a page handing you a figure for that owes you a source. Specifications you need to look up for your bike Value Why you need it Where to find it The viscosity grade your maker specifies for your machine and climate The grade is a manufacturer decision, not a general rule Owner’s manual The ambient temperature range your maker ties each grade it names to A grade is named for a climate and a duty, never in the abstract Owner’s manual The JASO performance class your maker asks for, if any Grade and friction class are separate requirements Owner’s manual Whether your maker publishes a second grade for sustained high ambient temperatures Some makers name one grade for all conditions and a different one above a stated ambient Owner’s manual The grade printed in the register row for the bottle you are holding It confirms the label against the filing record rather than against the front of the bottle The Filed Motorcycle Four Cycle Gasoline Engine Oil List Both halves of the grade name, exactly as your maker writes them The W half and the high temperature half are separate limits, so a bottle matching one half does not match the grade Owner’s manual When to stop and take it to a shop Stop if your manual gives a grade you cannot buy locally, because substituting a neighbouring grade is a decision for somebody who knows the machine and not a guess made in an aisle. Stop if the oil pressure warning is behaving oddly, since that is a diagnosis rather than a grade question, and a thicker oil is not a fix for it. Related checks JASO MA, MA2 and MB, what the classes actually mean Can you use car oil in a motorcycle? How to check an oil actually meets your bike's spec How to change motorcycle oil, and why there is no single procedure Frequently asked questions Is a 20W-50 thicker than a 10W-40? The two numbers are two separate limits, so the fair answer is that 20W-50 sits in a higher band at both ends of the range. What those bands are in measured units lives in the SAE grade table, which is sold rather than published, so we will not print figures for it. The grade to use is the one your maker specifies. Does a higher grade mean better protection? No. SAE's own scope says the standard defines a classification in rheological terms only, and that other oil characteristics are not considered or included. Protection depends on additive chemistry that the grade does not describe at all. Can I run a thicker grade in hot weather? Some manufacturers do publish more than one grade tied to ambient conditions, and if yours does, that is your answer. If it publishes a single grade for all conditions, changing it on your own reasoning is not something J300 or API supports, because neither of them publishes advice on substituting grades. Does the grade tell me whether an oil is safe for my wet clutch? No, and this is the mix-up that causes real damage. Flow behaviour and clutch friction are separate questions answered by separate standards. The friction answer is a JASO class, and whether it applies to your machine depends on whether the clutch runs in the engine oil at all. Where can I see the actual SAE grade table? From SAE, for a fee. SAE publishes the title, scope, committee and revision history of J300 free and sells the document. We have not reproduced the limits anywhere on this site, and if you find a page that has, ask yourself where it came from. About this guide Published by MotoGearRater. Reviewed by Tim Bob, motorcycle mechanic, 26 years in the trade. Universal procedure only, with no model-specific specifications. Read our editorial standards.

Warm the engine, get the bike level, drain from the plug, deal with the filter, refill short of full, then check the level the way your own manual says to check it. Everything but that last step is close to universal. The level check is not, and getting it wrong is how a careful job ends with an engine over or under full. Difficulty Time Tools Safety Beginner, with one step that needs the manual About an hour, most of it waiting Drain pan, correct socket, torque wrench, filter tool, funnel, gloves Hot oil, hot exhaust, a bike that can fall over Check first that this is the right procedure for your machine. Wet sump or dry sump, shared or separate oil for the gearbox, and spin on filter or cartridge all change what follows: start at how to change motorcycle oil. Before you touch anything Oil that has just been run is hot enough to scald, and the moment the plug clears its last thread the whole sump is coming at your hand. Drain it warm, not straight off a ride. The exhaust stays hot long after the engine is off, and on most machines it crosses the route your arm takes to reach the plug. Oil landing on a hot header smokes and can catch, so have the pan placed and the rags away from the pipe before anything is loosened. A bike can fall off a stand or a jack, and it falls towards whoever is kneeling beside it. You are pushing on a fastener underneath the machine, so put it on a stand rated for its weight, on flat solid ground rather than a slope, gravel, or a soft mat a stand foot will sink into. Wear eye protection and nitrile gloves. You are working underneath with the drain plug above your face, which gives used oil a clear path to your eyes. The US Environmental Protection Agency describes used motor oil as insoluble, persistent, slow to degrade, and able to contain toxic chemicals and heavy metals. EPA publishes no specific human health outcome from skin contact and we will not invent one, but there is no reason to wear it. See EPA on used oil. Never run an engine in an enclosed space, and the warm up that starts this job is where that gets forgotten. Have the new filter and sealing washer in your hand before anything is undone. What the drain plug method actually is It is gravity. On a wet sump engine the drain plug sits at or near the lowest point of the sump, so taking it out empties the sump from the bottom, removing what has settled as well as what is floating. It also puts the plug in your hand, the only moment in an oil change when you can look at the plug magnet and the threads. The alternative, extraction through the dipstick tube, skips both. Step one, warm the engine and get it level Warm oil is thinner and carries more of what is suspended in it out through the drain. A few minutes of idling or a short ride does it, outdoors. Then stop and wait, because there is a real gap between warm enough to flow and hot enough to burn through a glove. A sump drains from its lowest point, and a bike on its sidestand is not presenting that point to the plug. Get it upright on a centre stand, a rear stand, a lift or with a helper, level front to back as well as side to side, and block it so it cannot tip. Step two, drain Put the pan under the plug, allowing for the first of the oil coming out sideways before it straightens up. Open the filler cap so air can get in. Crack the plug loose with a properly fitting six point socket. If it is tight, improve tool engagement rather than adding leverage to a fastener that is rounding. Undo the last of it by hand, with inward pressure so it does not blow off the final thread, and let it run until it is a slow drip. Wipe the plug and look at it. This is the inspection you get for choosing this method. A magnet carrying a fine grey paste has been doing its job. What deserves attention is anything with a shape to it: flakes, chips, or fragments you can feel with a fingernail. Check the threads and the sealing face, then fit a new sealing washer. A crush washer seals by deforming and an O ring takes a set, so both are single use. Start the plug by hand and run it in several turns before any tool touches it. Cross threading an aluminium sump is the expensive mistake here. Tighten to the torque figure in your manual, with a torque wrench. Sump plugs thread into soft castings, so this is no place to work by feel. Step three, the filter A spin on canister is a sealed metal can that screws onto a threaded stub. A cartridge is a paper element inside a housing, behind a bolted cover. They need different tools and parts. For a spin on, move the pan under the filter first, because it is full and empties as it comes off. Undo it with a filter tool, then check the old rubber gasket came away with it and is not still stuck to the engine, because a doubled gasket is a guaranteed leak. Wipe the face, oil the new gasket, fit the filter by hand until the gasket meets the face, and tighten by the instruction printed on the filter body. For a cartridge, undo the cover bolts evenly and expect oil behind the cover. Note the order and orientation of everything that comes out, because there is often a spring or a seat behind the element and it goes back one way only. Replace the cover O ring. Step four, refill Say out loud that the plug is in and torqued and the filter is fitted, because the classic failure of this job is pouring fresh oil into an engine whose plug is still in the drain pan. Use a funnel and pour in noticeably less than the capacity figure in your manual. Manuals often quote different capacities with and without a filter change, and a sump that has not fully drained takes less than a dry one. Do not set the final level yet. Refit the cap, run the engine as the next step describes, shut it off and let it settle. Only then check the level by your manual’s method and bring it between the marks in small additions. Step five, run it and look for leaks Refit the filler cap or dipstick, start the engine and let it idle. After a filter change the oil pressure warning light can take slightly longer than usual to go out while the filter fills. If it does not go out, shut down immediately and find out why. Then look underneath: around the plug, around the filter, and on the floor. Wipe every surface clean beforehand, because residue from the job looks like a fresh leak. Then shut the engine off and let it settle, which is the state the level check in the next step needs. Look underneath again after your first ride. Step six, check the level, and this is where people get it wrong This is the step with the least universal answer and the most confident bad advice attached to it. All of the following vary by model: Whether the bike is read on the sidestand, on the centre stand, or held perfectly upright. Whether the engine should be cold, or warmed and then stopped for a specified settling period. Whether the engine should be running at idle or switched off while you read. Whether the dipstick is screwed fully home or simply rested on the threads. Whether you read a dipstick at all or a sight glass, which is read square on at eye level rather than from above. Those combinations are not interchangeable. A bike read on the sidestand when the manual specifies upright reads low, and topping up to the mark from that reading puts too much oil in the engine. We will not tell you which combination applies to your machine. It is a per model instruction and the owner's manual is where it lives. Anyone giving one confident answer for all motorcycles is describing the bike they own. Once you know the method, bring the level between the marks, adding small amounts and rechecking. Step seven, deal with the used oil Pour the drained oil into a sealable, leak proof container. EPA tells consumers to take care not to spill any as they collect it, and to check with local maintenance facilities, waste collectors and government waste officials for where to drop it off. Do not mix anything into it: petrol, coolant, brake fluid or solvent can make the whole lot unacceptable at a collection point. Drain the old filter and recycle it too. EPA states that used oil filters contain reusable scrap metal and that if properly drained they can be safely recycled, and that centres taking used oil usually take filters. It also gives a reason to bother: used oil from a single oil change can contaminate one million gallons of fresh water, a year's supply for fifty people. State rules can be stricter than federal ones. Specifications you need to look up for your bike Value Why you need it Where to find it Oil grade, and any classification the maker requires Choosing the oil at all Owner's manual Oil capacity, and whether it assumes a filter change Roughly how much to pour before you start checking Owner's manual Drain plug torque The plug threads into a soft casting Owner's or service manual Sealing washer and filter part numbers, and whether the filter is a spin on or a cartridge Buying the right parts and the right tool Parts catalogue or dealer Filter or filter cover torque Cartridge covers and some spin ons are torqued Factory service manual Level check method: stand or upright, hot or cold, running or stopped, dipstick screwed in or rested The one step here with no universal answer Owner's manual Drain point locations, and whether a strainer is serviced Both get missed on bikes that have them Factory service manual When to stop and take it to a shop Stop if the plug rounds off, spins without tightening, or comes out with aluminium threads on it. Stop if the magnet or the pan holds metal with a shape to it, or if the drained oil is milky. Both are findings about the engine, not the oil change. Stop if a cartridge cover is warped, a sealing face is scored, or the oil pressure warning light does not go out after the first restart. Stop if you cannot find the manufacturer's level check method for your model. Guessing it is the likeliest way to hurt an engine on an otherwise correct job. Related checks How to change motorcycle oil, and which procedure your bike needs Changing oil with a vacuum extractor, and when it is a bad idea Drain plugs, crush washers and stripped threads What to do with used motorcycle oil Frequently asked questions Does the engine have to be warm before I drain it? Warm oil flows faster and carries more of what is suspended in it out of the sump. Warm is not hot, though, and whether your manufacturer specifies warm or cold is a per model instruction in the owner's manual. Can I reuse the drain plug washer? Treat it as single use. A crush washer seals by deforming and an O ring takes a permanent set once squeezed. Reusing either is the usual reason a plug weeps, and the cure people reach for is more torque, which is how sump threads get stripped. How tight should the drain plug be? To the torque figure in your manual, with a torque wrench. We do not publish one. Thread size, washer type and casting material differ between machines, and a number taken from a guide about a different bike is a reliable way to strip a sump. Do I have to change the filter every time? Whether your manufacturer specifies a new filter at every oil change or at alternate ones is in the maintenance schedule in your owner's manual. What is always true is that a filter holds oil, so a change including the filter takes more than one that does not. That is why the level check, not the capacity figure, tells you when to stop. About this guide Published by MotoGearRater. Reviewed by Tim Bob, motorcycle mechanic, 26 years in the trade. Universal procedure only, with no model-specific specifications. Read our editorial standards.

There is no single motorcycle oil change procedure, and any guide that gives you one is describing its author's bike. Three things about your machine decide what the job actually is: whether the oil lives in the sump or in a separate tank, whether that same oil also lubricates the gearbox and the clutch, and whether the filter is a spin on canister or a cartridge in a housing. Establish those three, and the rest of the job follows. Difficulty Time Tools Safety Beginner to intermediate, depending on the answers below About an hour once you know which procedure applies Depends on the filter type and the drain method Hot oil, hot exhaust, a bike that can fall over This page routes. It does not repeat the step by step, because the steps differ depending on your answers, and the linked pages carry them. Before you touch anything Oil that has just been run is hot enough to scald, and it leaves the engine fast when the plug clears its threads. Warm is what you want, not hot off a ride. The exhaust stays hot long after the engine is off, and it usually runs right under where you will be working. Oil landing on a hot header smokes and can catch. A bike can fall off a stand or a jack, and it falls towards whoever is kneeling beside it. Use a stand rated for the machine on flat solid ground, and get it upright and level before anything comes undone. Wear eye protection and nitrile gloves. The US Environmental Protection Agency describes used motor oil as insoluble, persistent, slow to degrade, and able to contain toxic chemicals and heavy metals. EPA publishes no specific human health outcome from skin contact and we will not invent one, but there is no reason to wear the stuff. See EPA on used oil. Never run an engine in an enclosed space. Warming the engine is the first step of this job and it is where that gets forgotten. Why there is no single procedure An oil change is four things: get the old oil out, deal with the filter, put the right oil back, confirm the level. All four are arranged differently across motorcycles. Where the oil sits decides where it drains from and how many drain points there are. Whether the gearbox and clutch share that oil decides which oil is allowed in the engine at all. How the filter is mounted decides your tools and your parts. And the level check, the step that confirms the whole job, has no universal method: whether a bike is read on the sidestand or upright, hot or cold, running or stopped is model specific and lives in the owner's manual. So work through the three questions below before you touch a spanner. Question one, wet sump or dry sump On a wet sump engine the oil is held in the sump underneath the engine, and a drain plug at or near its lowest point empties it. This is the arrangement most riders have, and the one nearly every generic guide assumes. A dry sump engine keeps its oil in a separate tank, with pumps moving it in and out of the engine. That changes the job in a way no generic guide accounts for: there is usually more than one place oil sits, and emptying one does not empty the others. Drain what you think is the sump, refill to the capacity figure, and the engine can end up holding the wrong amount. Your service manual is the authority on which you have and where every drain point is. A separate oil tank with its own filler cap is a hint, not proof. If your machine is dry sump, start at the dry sump oil change. Question two, does the engine share its oil with the gearbox and clutch This is the question that decides which oil, and the one most often got wrong. On the great majority of four stroke motorcycles a single body of oil lubricates the crankshaft and valvetrain, the gearbox gears, and a wet clutch whose friction plates run immersed in it. The Japan Lubricating Oil Society describes this architecture as one in which a lubricating oil is used commonly for the engine, clutch and transmission, and it is the reason a motorcycle specific oil standard exists at all. JASO T903 was written to identify oils suited to it, and JALOS states in its implementation manual that there are concerns low friction and low viscosity oils, used in motorcycles, may cause clutch slippage and transmission gear pitting wear. Not every machine is arranged that way. Harley-Davidson's own Formula+ product page documents the opposite case, listing models on which the wet clutch runs in the primary chaincase lubricant rather than the engine oil, and stating that lubricant is not for use in the crankcase. Where the clutch and gearbox live in separate cavities with their own fluids, or the clutch is dry and runs in air, the engine oil never reaches the friction plates, so the JASO friction classification has no bearing on the clutch. Which arrangement your bike uses is a per model fact and it has to come from your own manufacturer's documentation. We do not publish a model list, because no primary source we could verify publishes one. Follow it up in what the JASO classes mean, whether car oil belongs in a motorcycle, and for separate-fluid machines, engine, primary and transmission fluids. Question three, spin on canister or cartridge A spin on filter is a sealed metal can that screws onto a threaded stub on the engine. You take the whole thing off with a filter tool and throw it away. A cartridge filter is a paper element inside a housing on the engine, reached by unbolting a cover, and only the element is replaced. They need different tools and different parts. A spin on can leave its old rubber gasket stuck to the engine, and a doubled gasket leaks. A cartridge usually has a cover O ring and often a spring or seat behind the element that goes back one way only. Work out which you have before buying anything: spin on versus cartridge. Then choose how you get the oil out With those three answered, there are two ways to do the job. The drain plug method empties the sump from its lowest point and puts the plug in your hand, so you get to read the plug magnet and inspect the threads. A vacuum extractor pulls the oil out through the dipstick tube, which is a real convenience on a faired bike, and skips both of those inspections. Two things are worth reading before either: whether to drain hot or cold, and crush washers and stripped plug threads, the failure that turns a simple job into a repair. Either way the old oil has to go somewhere: how to dispose of used motorcycle oil. Choosing the oil itself The grade on the bottle is not the whole answer. SAE J300, the standard behind names like 10W-40, defines limits for engine oils in rheological terms only, and SAE states plainly that other oil characteristics are not considered or included. A grade describes flow behaviour and nothing about clutch friction or additive chemistry. What your manufacturer requires, and how to check that a bottle actually meets it, is covered in viscosity grades explained and how to verify an oil meets your manufacturer specification. Specifications you need to look up for your bike Value Why you need it Where to find it Wet sump or dry sump, and every drain point Question one, and it changes the whole procedure Factory service manual Whether the engine oil also lubricates the gearbox and clutch Question two, and it decides which oil Owner's manual and factory service manual Filter type, part number and cover torque Question three, and it decides your tools Parts catalogue and factory service manual Oil grade, and any classification the maker requires Choosing the oil at all Owner's manual Oil capacity, and whether it assumes a filter change Roughly how much to pour before you start checking Owner's manual Drain plug torque and sealing washer part number The plug threads into a soft casting Owner's or service manual Level check method: stand or upright, hot or cold, running or stopped, dipstick screwed in or rested The step that confirms the whole job, and it has no universal answer Owner's manual The maintenance schedule When the change and the filter are actually due Owner's manual When to stop and take it to a shop Stop if you cannot establish, from the manufacturer's own documentation, whether your bike is wet or dry sump and where all its oil sits. Stop if the drain plug rounds off, spins without tightening, or comes out with aluminium threads on it. Stop if the plug magnet or the drained oil carries metal with a shape to it, or if the oil is milky. Those are findings about the engine, not about the oil change. Stop immediately if the oil pressure warning light does not go out after the first restart. Stop if you cannot find your manufacturer's level check method. Guessing it is the likeliest way to hurt an engine on an otherwise correct job. Related checks The drain plug oil change, step by step Changing oil with a vacuum extractor, and when it is a bad idea The dry sump oil change Oil filter change, spin on versus cartridge Hot or cold, when to drain Crush washers and stripped drain plug threads JASO MA, MA2 and MB explained Can you use car oil in a motorcycle Viscosity grades explained How to verify an oil meets your manufacturer specification Engine, primary and transmission fluids on separate-cavity machines How to dispose of used motorcycle oil Frequently asked questions How do I know whether my bike is wet sump or dry sump? The factory service manual settles it, and nothing else does reliably. A separate oil tank, or more than one drain point, is a hint rather than proof. It matters because draining one reservoir on a dry sump machine does not empty the others, and refilling to the capacity figure afterwards can leave the engine holding the wrong amount. Does my bike need motorcycle specific oil? It depends on the answer to question two. Where the engine oil also lubricates a wet clutch and the gearbox, the oil's friction behaviour is part of the clutch design, which is why JASO T903 exists, and JALOS warns that low friction and low viscosity oils may cause clutch slippage and transmission gear pitting wear. Where the clutch is dry or runs in its own fluid, the engine oil never touches the friction plates. Which applies to your machine is a per model fact from your own manufacturer. Is the viscosity grade on the bottle enough to choose an oil? No. SAE says J300 defines limits for engine oils in rheological terms only, and that other oil characteristics are not considered or included. The grade describes flow behaviour. It tells you nothing about clutch friction, additive chemistry or whether the oil suits a shared sump. How often should I change it? We do not publish intervals. The maintenance schedule in your owner's manual is written for your machine and how it is used, and it is the only figure worth following. Anyone quoting one mileage for all motorcycles is guessing. About this guide Published by MotoGearRater. Reviewed by Tim Bob, motorcycle mechanic, 26 years in the trade. Universal procedure only, with no model-specific specifications. Read our editorial standards.

A regulator rectifier does two jobs: it converts the stator's alternating current into direct current, and it caps the voltage so the battery is not overcharged. It fails in two directions. Either it stops charging, or it stops regulating and overcharges. Test the battery, the connectors and the stator first, because all three get blamed on the regulator and all three destroy replacement regulators. Difficulty Time DIY cost Tools Safety Level 3, intermediate 30 to 60 minutes $0 to diagnose Multimeter with DC volts and diode mode Running engine, hot component, battery Work through the charging system sequence before this page. If you have not cleared the battery, the connectors and the stator, testing the regulator is premature. Before you touch anything Regulators shed heat and can be genuinely hot after a ride, hot enough to burn. Let it cool before handling. Keep leads clear of the chain, belt and cooling fan while the engine runs, and do not run an engine in an enclosed space. Never disconnect the battery while the engine is running to test anything, because that can destroy the regulator and other electronics. Stator output measured with the plug disconnected is live alternating current at a much higher voltage than the battery, so read the warning in step two before probing it. The two failure modes, and how they present Symptom at the battery, engine running above idle Failure mode What happens if you keep riding Voltage does not rise above resting Not charging. Rectifying or output side has failed You run on the battery until it is flat, then you stop Voltage climbs well above about 15 volts Not regulating. The capping function has failed The battery is boiled and cooked, and other electronics are stressed. Stop riding Voltage swings erratically Intermittent, often a connector rather than the unit Unpredictable, and it will strand you eventually The general expectation for a healthy 12 volt system is a clear rise above resting voltage, commonly in the region of 13.5 to 14.5 volts. Between about 14.5 and 15 volts is a grey band where plenty of healthy systems sit, particularly with a cold battery. Your model's specified target and the rpm at which to measure it are in the factory service manual, and a borderline case should be judged against that figure rather than this range. Step one, inspect the connector, because it is usually the story The plug between stator and regulator carries the machine's full charging current. On many motorcycles it is commonly the first thing to fail in the whole system, and it fails by overheating. Unplug it and examine both halves closely. Look for brown or black discolouration, melted or deformed plastic, and pins that are green, blackened or pushed back into the housing. Check that each pin still grips firmly. A spread female terminal makes poor contact, heats up, and the heat makes the contact worse. Check the regulator's ground connection and its output wire to the battery for corrosion. If the connector is damaged, replace it properly with correctly rated terminals. Cleaning up a burnt connector and pushing it back together restores the fault within weeks, and it will take the new regulator with it. Step two, confirm the input is there A regulator with no input cannot produce an output, and a healthy regulator will look dead if the stator is not feeding it. Unloaded stator output is far higher than battery voltage, commonly tens of volts at idle and well over a hundred volts at raised rpm, so set a manual-ranging meter to its highest AC volts range first, hold the probes by their insulated bodies, and keep the disconnected plug halves clear of each other and the frame. With the stator unplugged from the regulator and the engine running, measure AC volts across each pair of stator leads. If those readings are absent, very low, or wildly unequal between pairs, your problem is upstream. Go to how to test a motorcycle stator. Only once you have confirmed a healthy AC input does a regulator become the prime suspect. Step three, the diode test The rectifying half of the unit is built from diodes, and a diode's defining behaviour is that it conducts in one direction and blocks in the other. That is what diode mode on a multimeter checks, and it can be done on the bench with the unit unplugged. Disconnect the regulator rectifier completely, both the stator side and the battery side. Set the meter to diode mode, the symbol that looks like a triangle pointing at a line. Test between each alternating current input pin and the direct current positive output, in both directions. Then test between each alternating current input pin and the direct current negative or ground pin, in both directions. You are looking for a consistent pattern: conduction one way and no conduction the other way, on every path, with the readings in each direction similar to one another across the pins. What you find Interpretation Conducts in one direction only, consistently on every path The diodes are behaving. The rectifying half is probably sound Conducts in both directions on any path A shorted diode. The unit has failed Conducts in neither direction on any path An open diode. The unit has failed One path behaves very differently from its equivalents Suspicious. Compare against the service manual values Three honest limitations of this test. First, it checks the rectifying half, not the regulating half. A unit can pass a diode test and still fail to cap voltage, which is why the running measurement at the battery matters more. Second, the numbers your meter displays in diode mode depend on the meter as well as the component, so judge the pattern and the consistency rather than chasing an exact figure. Where your service manual publishes expected values, use those. Third, and most important, this test assumes a simple diode bridge. Many motorcycle regulators are shunt type, built around thyristors rather than plain diodes, and some newer units are MOSFET based. On those the clean pattern above does not appear even when the unit is perfectly healthy, so a diode-mode result that looks like a failure is not on its own grounds to condemn one. If your unit does not give a consistent pattern, judge it on the running measurement at the battery instead. Step four, confirm with the engine running The definitive test is the one at the battery. Reconnect everything, start the engine, raise the revs off idle and hold them steady, and watch DC volts at the battery terminals. A unit that cannot lift voltage above resting, with a proven healthy stator and clean connectors, has failed. A unit that lets voltage climb above roughly 15 volts has failed in the other direction and should be replaced before it destroys the battery. Specifications you need to look up for your bike Value Why you need it Where to find it Charging voltage target and the rpm to measure at Judging step four Factory service manual Regulator rectifier diode test values Judging borderline diode readings Factory service manual Stator AC output at rpm Confirming the input in step two Factory service manual Wiring diagram and connector pinout Knowing which pin is which before probing Factory service manual Regulator mounting torque Refitting without stripping a mount Factory service manual The pinout matters more than people expect. Probing the wrong pins produces a confident wrong answer, and pin arrangements vary by model. When to stop and take it to a shop Stop and do not ride if voltage is above roughly 15 volts, because each further mile damages the battery and stresses the electronics. Stop if you find melted wiring inside the main loom rather than at a serviceable connector. And stop before replacing a regulator for the second time without having found the reason the first one died, since a burnt connector or a shorting stator will consume replacement units indefinitely. Related checks The full charging system sequence Testing the stator Battery keeps going flat Multimeter basics including diode mode Frequently asked questions What are the symptoms of a bad regulator rectifier? The reliable symptoms are electrical, not sensory. Either the battery is not being charged, so voltage at the battery does not rise with engine speed, or it is being overcharged, so voltage climbs abnormally high and the battery becomes hot, swollen or gassy. Dim or flickering lights and a bike that runs progressively worse as the battery drains are downstream effects of the first case. Can I test a regulator rectifier with a multimeter? You can test the rectifying half using diode mode, checking that each path conducts one way and blocks the other. You cannot properly test the regulating half on the bench, because that function only operates with the system running. That is why the running voltage measurement at the battery is the test that decides it. Why does my regulator get so hot? Regulators dissipate surplus energy as heat by design, so warm to hot is normal. What is not normal is heat that has discoloured or melted the connector, or a unit hot enough that the surrounding wiring has suffered. Many machines mount the regulator in the airflow for exactly this reason, so a fairing change or an accessory that blocks airflow can contribute. Will a bad regulator rectifier drain my battery when parked? It can. A failed diode can allow current to leak back through the unit while the bike is switched off, which shows up as a parasitic draw. If your standing draw test points at the charging circuit, unplug the regulator and repeat the measurement. See testing for a parasitic draw. Is an aftermarket regulator a good idea? Quality varies widely. What matters more than brand is fixing the reason the original failed, and making sure the replacement has adequate cooling and a sound connector. A well-made unit fitted to a burnt connector will still fail. About this guide Published by MotoGearRater. Universal procedure only, with no model-specific specifications. Not reviewed by a qualified motorcycle technician, and we say so rather than implying a review that has not happened. Read our editorial standards.

A stator is tested two ways. With the engine running, unplug it from the regulator and measure alternating current output between each pair of leads: the readings should be present, rise with engine speed, and be similar across pairs. With the engine off, measure resistance between the leads, which should be low and even, and, on a three-phase stator, from each lead to the engine case, which should show nothing at all. Difficulty Time DIY cost Tools Safety Level 3, intermediate to test 30 to 45 minutes to test $0 to diagnose Multimeter with AC volts and resistance Running engine, live AC output, hot engine Test the battery and the connectors first. Work through the charging system sequence before condemning a stator, because a burnt connector produces identical symptoms and costs a fraction as much to fix. Before you touch anything The stator output is live alternating current while the engine runs, and it is not trivial. Unloaded output is far higher than battery voltage, commonly tens of volts at idle and well over a hundred volts at raised rpm, so set a manual-ranging meter to its highest AC volts range before you start. Do not hold bare terminals. Hold the probes by their insulated bodies, and keep the disconnected plug halves from touching each other or the frame. Keep leads and sleeves away from the chain or belt, the cooling fan and the exhaust. Support the bike properly, transmission in neutral, and do not run an engine in an enclosed space. Let a hot engine cool before working near the cases. Never disconnect the battery while the engine is running. What a stator actually is The stator is a ring of copper windings that stays still while a magnetised rotor spins past it, generating alternating current. It typically has three output leads, though some machines differ, and those leads run to the regulator rectifier which converts and controls what the stator produces. Most stators sit inside an engine side case, which is why replacing one is a bigger job than testing one. Stators fail in two ways. A winding can short to the engine case, which is a hard failure you can measure with the engine off. Or the insulation can break down between windings so that output falls, which usually shows up as reduced or uneven AC output with the engine running. Test one, alternating current output with the engine running This is the test that matters most, because it measures the stator doing its actual job. Find the connector between the stator and the regulator rectifier and unplug it. You will test on the stator side, the half whose wires disappear towards the engine. Set the meter to alternating current volts. This is the AC setting, not the DC setting used everywhere else on the bike. Getting this wrong is the most common error in this test and produces a near-zero reading on a healthy stator. Start the engine and hold a steady raised engine speed. Measure between lead one and lead two. Then lead two and lead three. Then lead one and lead three. On a three-lead stator that is three readings. What you see Interpretation All three readings present, similar to one another, and rising as revs rise The stator is producing. Compare the figures against your service manual specification One pair much lower than the others A weak or partially failed winding One pair reading nothing An open winding, or a broken lead All three very low or absent Failed stator, broken loom, or on some machines a rotor that has lost its magnetism The actual voltage a healthy stator should produce, and the engine speed at which to measure it, are specific to your model. We do not publish them, because the figure varies enormously between machines and a number taken from a forum thread about a different bike will lead you to replace a healthy part. Your factory service manual has both. What you can judge without the manual is the comparison between pairs. Readings that differ substantially from one another on the same stator are a genuine finding whatever the absolute numbers. Test two, resistance between the leads, engine off Engine off, stator still unplugged. Set the meter to resistance, the ohms setting. Measure between each pair of leads, the same three combinations as before. On a healthy stator these readings are low and close to one another. A reading of infinite resistance on any pair means an open circuit in that winding. Wildly unequal readings suggest a partial short between windings. The specified resistance is a model-specific value from the service manual. Note also that cheap meters are not accurate at the very low resistances involved, and that meter lead resistance itself is part of what you measure. Touch the probes together first and note that reading, then subtract it. Because of this, treat the comparison between pairs as the more reliable signal. Test three, continuity to ground, and this one is decisive Still on the resistance setting, or on the continuity setting if your meter has one. Put one probe on a bare, clean, unpainted part of the engine case, and the other on each stator lead in turn. On a three-phase stator, none of the output leads should show continuity to the engine case. Infinite resistance, no beep, nothing. Any continuity between a stator lead and the case means a winding has shorted to it, and the stator has failed. This test needs no model-specific value to interpret, which makes it the most useful measurement on the page. Confirm first, from the wiring diagram, that your machine is three-phase with no deliberately grounded lead. Some single-phase charging systems, and some separate lighting or charging coils, ground one lead to the case by design. On those a continuity reading is normal rather than a failure, and condemning the stator on it would mean opening an engine case for nothing. Make sure your ground probe is on clean metal. Paint, oil or an anodised surface will give you a false pass. What to check before you buy a stator Stator replacement usually means draining a fluid, removing an engine side cover and fitting a new gasket, which is a real job. Before committing, rule out the cheap causes that produce the same symptoms. The connector. Burnt or corroded plugs between stator and regulator are extremely common and produce low or missing output. Inspect both halves. The loom. Trace the stator leads where they leave the engine. Chafing against the frame or the swingarm pivot area happens. The regulator. A failed regulator can present as a charging fault that feels like a stator problem. Test it: how to test a motorcycle regulator rectifier. The battery. A battery that will not hold charge makes a healthy charging system look useless. Specifications you need to look up for your bike Value Why you need it Where to find it Stator AC output voltage, and the rpm to measure at Judging test one Factory service manual Stator coil resistance between leads Judging test two Factory service manual Number of stator leads and the wiring diagram Knowing what you are probing Factory service manual Side cover fastener torque and sequence Replacement, if you go ahead Factory service manual Fluid type and capacity for the case you open Refilling correctly after replacement Owner's manual and factory service manual When to stop and take it to a shop Stop before opening an engine case if you do not have the correct gasket, the fluid to refill it and the torque specification for the cover fasteners. Stop if the rotor also needs attention, since rotor removal often requires a specific puller and can involve substantial torque. And stop if you find metal debris in the drained fluid, because that is a finding about the engine and not about the charging system. Related checks The full charging system sequence Testing the regulator rectifier Battery keeps going flat Multimeter basics, including AC volts and resistance Frequently asked questions How do I know if my stator is bad without removing it? All three tests on this page are done at the connector, with the stator still in the engine. The continuity-to-ground test in particular is decisive and needs no model-specific figures. You only remove the stator once testing has condemned it. My meter reads almost nothing on the stator output. Is it dead? Check the meter setting first. Stator output is alternating current, and a meter left on DC volts will show almost nothing on a perfectly healthy stator. This single mistake is responsible for a lot of healthy stators going in the bin. Can a stator fail intermittently? Yes. Insulation breakdown can worsen with heat, so a stator can behave acceptably cold and fail once the engine is up to temperature. If your charging fault appears only after a period of riding, repeat the running output test with the engine hot as well as cold. Will a bad stator drain the battery when the bike is parked? A stator on its own generally does not, since it is a generator rather than a load. A failed diode inside the regulator rectifier can leak current back and drain a parked battery. If the battery goes flat while standing, test for a parasitic draw. Should I replace the regulator at the same time as the stator? Only if you have tested it and it has failed, or if the connector between them burnt badly enough to suggest both took damage. Replacing parts in pairs on principle is expensive guesswork. What is genuinely worth replacing at the same time is the connector, since it is cheap and it is the usual cause. About this guide Published by MotoGearRater. Universal procedure only, with no model-specific specifications. Not reviewed by a qualified motorcycle technician, and we say so rather than implying a review that has not happened. Read our editorial standards.

Four multimeter settings solve most motorcycle electrical faults: DC volts to measure what a circuit has, resistance to check whether a path exists, continuity to find breaks quickly, and DC current to find what is draining a parked battery. Add voltage drop testing, which is just DC volts used cleverly, and you can find faults that resistance testing misses completely. Difficulty Time Cost Tools Safety Level 1, beginner 30 minutes to learn A usable meter from about $20 A digital multimeter with a 10A jack Low, with two important exceptions below The two things that damage a meter or a bike Almost every multimeter accident comes from one of these two mistakes. Learn them before anything else. Never put the meter in current mode across a battery. In current mode the meter is close to a piece of wire. Placed across a battery it becomes a short circuit, and it will blow its fuse at best. Current mode goes in line with a circuit, never across a source. Never crank the engine with the meter in series. A starter draws well over a hundred amps and the meter's high current jack is fused for ten or twenty. This is how meters die during parasitic draw testing. Both input jacks are fused, but at very different ratings. The volts and ohms jack is usually protected at only a few hundred milliamps, while the 10A jack is rated for the current its name implies. Move the red lead into the socket marked 10A or 20A whenever you measure current, and move it back to the volts and ohms socket afterwards. Leaving the lead in the current jack and then probing a live circuit expecting a voltage reading is the classic way to destroy a meter. Setting up the meter The black lead goes into the socket marked COM, and it stays there for everything. The red lead goes into the socket marked with volts and ohms for most work, and into the 10A socket only when measuring current. Many cheap meters are manual ranging, which means you choose a range higher than the value you expect. For a 12 volt system, select the 20 volt DC range. An autoranging meter picks for itself. Either is fine. DC volts, the setting you will use most Set the dial to DC volts, marked with a V and a straight line, sometimes with a dashed line beneath it. Red probe to the more positive point, black probe to ground or the negative side. If you get the probes the wrong way round on a digital meter, nothing is harmed, the reading simply shows a minus sign. What you can do with it: Battery state of charge. Probes across the battery terminals with everything off, ideally after the bike has rested a few hours. For a conventional or AGM 12 volt lead-acid battery, roughly 12.6 to 12.8 volts is full, around 12.4 volts is roughly three quarters, and below 12.0 volts is deeply discharged. Lithium batteries read differently and should be judged against the maker's figures. Charging voltage. Same probes, engine running above idle. A healthy 12 volt system typically rises clearly above resting, commonly into the region of 13.5 to 14.5 volts. Your model has a specific target in its service manual. Is this wire live. Black probe on a clean ground, red probe on the wire or terminal. This is how you trace power through a circuit from the battery to whatever has stopped working. Voltage drop, the technique that finds hidden faults This is the most useful technique on the page, and it is the one riders are least likely to have tried. A corroded connection can measure fine on resistance and still fail completely when real current flows through it. Resistance testing uses the meter's tiny internal current, which sneaks through a poor connection quite happily. Only under load does the fault appear, and it appears as voltage lost across the connection. To measure it, stay on DC volts. Put one probe on each side of the connection you suspect, then operate the circuit so current flows, and read the display. You are measuring what that one junction is stealing. What you are testing Widely used workshop rule of thumb A cable or a connection in a high current path Under about 0.2 volts lost A ground connection Under about 0.1 volts lost Those are general rules of thumb rather than manufacturer specifications. The reliable use of them is comparative: test every connection in a path, and the one with the largest drop is where your current is going. This is how a bad earth strap that looks perfect gets caught, and it is the technique behind the clicking guide. Resistance and continuity Resistance mode, marked with the ohm symbol, measures how much a path opposes current. Continuity mode, usually marked with a sound symbol, is the same measurement with a beeper attached so you can watch your hands instead of the display. Always test resistance with the circuit disconnected from power. Measuring resistance on a live circuit gives nonsense readings and can damage the meter. Testing a fuse. Pull it, probe both blades. A good fuse beeps or reads near zero. A blown one reads infinite. Testing a switch. Disconnect it, probe its two terminals, and operate it. It should read near zero in one position and infinite in the other. Kill switches, clutch switches, neutral switches and side stand switches all test this way, and this is how you catch the interlock faults in the no crank and no click guide. Testing a wire for a break. Disconnect both ends, probe each end. Near zero means the wire is intact. Infinite means it is broken somewhere. Testing for a short to ground. Probe from a disconnected wire to bare engine or frame metal. Any continuity where there should be none is a short. This is exactly the decisive test in stator testing. One practical note: touch the two probes together before a low resistance measurement and note what the meter reads. That is your lead resistance, and on cheap meters it is not zero. Subtract it. AC volts, for the charging system only Marked with a V and a wavy line. On a motorcycle the main use is measuring the alternating current a stator produces before the regulator rectifier converts it, and it also applies to pickup and pulse generator coils. Unloaded stator output is far higher than battery voltage, commonly tens of volts at idle and well over a hundred volts at raised rpm, so start a manual-ranging meter on its highest AC range rather than on a 20 volt range. Leaving the meter on DC while testing a stator shows almost nothing on a perfectly healthy component, and it is responsible for a great many unnecessary stator purchases. Full method in how to test a motorcycle stator. DC current, for finding a drain Red lead into the 10A jack, dial to the matching DC current range, and the meter goes in series so all the current flows through it. On a motorcycle this has one main use: measuring what a parked bike is drawing. The full procedure, including the waiting that most people skip, is in how to test for a parasitic draw. Diode mode Marked with a triangle pointing at a line. It applies a small voltage and tells you whether current passes. A working diode conducts in one direction and blocks in the other. On a motorcycle this is used mainly on the regulator rectifier, covered in how to test a motorcycle regulator rectifier. Judge the pattern of conduction rather than chasing an exact displayed number, since that number depends partly on the meter. Buying a meter For motorcycle work you need DC volts, AC volts, resistance, continuity with a beeper, diode mode and a fused 10A current range. That is it. Inexpensive meters do this adequately. What separates a better meter is higher rated input protection, decent probes, and a display you can read in a dim garage. A set of crocodile clip leads is the single most useful accessory, because most of these tests need both hands free. Specifications you need to look up for your bike Value Why you need it Where to find it Charging voltage target and the rpm to measure at Judging a charging test Factory service manual Stator output and coil resistance Judging a stator test Factory service manual Switch and sensor resistance values Judging a component test Factory service manual Maximum acceptable standing current draw Judging a parasitic draw test Factory service manual Wiring diagram Knowing what should be live and when Factory service manual A meter tells you what a circuit is doing. Only the manual tells you what it should be doing. That is why we publish the method here and point you at the document for the numbers. When to stop and take it to a shop A meter finds faults, it does not fix wiring. Stop if you find chafed, melted or discoloured wiring inside a main loom, because a poor harness repair is a fire risk. Stop if a fault is intermittent and will not reproduce, since chasing one of those can consume days and a workshop with a wiring diagram and proper probes will find it faster. And stop before probing an anti-lock braking system or an immobiliser, because those usually need manufacturer software rather than a meter. Related checks The full no-start guide Voltage drop testing a clicking starter Testing the charging system Testing for a parasitic draw Frequently asked questions What multimeter settings do I need for motorcycle work? DC volts for almost everything, resistance and continuity for switches, wires and fuses, AC volts for stator output, DC current for finding a parked drain, and diode mode for the regulator rectifier. Six settings cover essentially all of it. Why does my meter read zero when I test the stator? Because it is almost certainly set to DC volts. A stator produces alternating current, so the meter must be on AC volts. Check this before concluding anything about the component. Can I damage my motorcycle with a multimeter? Used in voltage or resistance mode, the risk is very low. The real risk is current mode, where the meter behaves like a wire. Placing it across a battery, or cranking the engine while it is in series, is where damage happens. Keep the red lead out of the 10A socket unless you are deliberately measuring current. What is the difference between continuity and resistance? They measure the same thing. Continuity mode simply beeps below a low threshold so you can work without watching the screen. Use continuity for yes-or-no questions like whether a fuse is intact, and resistance when the actual value matters, such as a coil. Why test voltage drop instead of resistance on a cable? Because a poor connection can pass the meter's tiny test current perfectly well and still fail under the hundreds of amps a starter demands. Voltage drop tests the connection under real load, which is the condition that matters. It finds faults that a resistance test declares healthy. About this guide Published by MotoGearRater. Universal procedure only, with no model-specific specifications. Not reviewed by a qualified motorcycle technician, and we say so rather than implying a review that has not happened. Read our editorial standards.

A starter relay is an electrically operated switch. A small current from the starter button energises a coil, the coil pulls contacts together, and those contacts pass the very large current the starter motor needs. Test it in two halves: does the coil energise, and do the contacts actually pass current. A relay that clicks has a working coil and may still have burnt contacts. Difficulty Time DIY cost Tools Safety Level 2 to 3 30 to 45 minutes $0 to diagnose Multimeter, spanners, insulated screwdriver if jumping Very high current, accidental cranking, arcing The terms overlap in everyday use. On most motorcycles the component is a relay or solenoid mounted near the battery with two heavy cables and two small wires. Some machines also have a solenoid built into the starter itself. Everything below applies to the separate relay. Before you touch anything This is the highest current circuit on the motorcycle. Treat it with the same respect as any other high energy source. Transmission in neutral and the bike properly supported before any test that could crank the engine. A bike that starts in gear will move. Remove rings and metal watch straps. A ring bridging a terminal to the frame causes severe burns. Eye protection. These terminals can arc brightly. Disconnect the negative battery lead first whenever you are removing or refitting the heavy cables, and reconnect it last. Never lay tools across the relay terminals. Understanding the four terminals Terminal What it is Large terminal one Heavy cable direct from the battery positive. Live at all times Large terminal two Heavy cable to the starter motor. Live only while the relay is closed Small wire one Coil feed, energised when you press the starter and the interlocks are satisfied Small wire two Coil ground or the return path through the interlock circuit Which small wire does which varies by machine, and the wiring diagram in the factory service manual is the only reliable guide. Test one, does the coil energise Put your hand or ear on the relay and press the starter. A distinct click means the coil is receiving current and the armature is moving. No click at all means the coil side of the circuit has a problem, and the fault is upstream in the button, the interlocks, a fuse or the wiring. That is the no crank and no click path. To confirm electrically, set the meter to DC volts, black probe on a good ground, red probe on the coil feed wire at the relay, and press the starter. Battery voltage appearing there means the switch, the interlocks and the wiring are doing their job and delivering the signal. Nothing appearing there means they are not, and the relay is innocent. Test two, do the contacts pass current This is where a clicking relay is caught out. The coil pulls in, you hear the click, and the contacts inside are too burnt to pass the current the starter needs. Set the meter to DC volts. Put one probe on the large battery-side terminal and the other on the large starter-side terminal. Press the starter for a second or two and read the display. Reading across the two large terminals while cranking Interpretation A very small drop, a fraction of a volt The contacts are passing current properly. The relay is fine A large drop, most of battery voltage appearing across the relay The contacts are burnt or not closing. The relay has failed This is voltage drop testing, and it is the definitive test for this component. A widely used workshop rule of thumb is that a good high current connection loses under about 0.2 volts. The relay is effectively a connection, so the same thinking applies. The technique is explained in full in how to use a multimeter on a motorcycle. Test three, the coil resistance With the relay disconnected, measure resistance across the two small terminals. An open circuit means the coil has failed internally, and the relay will never click. A very low reading suggests a shorted coil. The correct resistance value is a model-specific specification in the factory service manual, so use that to judge a borderline reading. What you can conclude without it is an open circuit, which is unambiguous. The jumper test, and its real risks Bridging the two large terminals bypasses the relay entirely and sends battery current straight to the starter. If the engine then cranks, the relay or its coil circuit is at fault. If it does not, the starter or its ground is at fault. It is a genuine test and it is also the most dangerous thing on this page. Be honest with yourself about whether you need it, because the voltage drop test in test two answers the same question without the hazard. If you do it: Transmission in neutral. The engine will crank, and if it starts in gear the bike will move. Expect a substantial spark at the moment of contact. The relay usually sits right beside the battery, and a lead-acid battery vents hydrogen, so ventilate the area and keep the arc away from the battery and its vent. Nothing flammable nearby, no fuel vapour, eye protection on. Decide deliberately whether the ignition is on or off, because with it off the engine only cranks, while with it on the engine may actually start while your hands are at the terminals. Use a properly insulated tool with a heavy shank. A thin screwdriver will heat, pit and can weld itself across the terminals. Make contact briefly. Do not hold it while the starter labours. Keep your face and hands clear of the terminals. Some machines have safety interactions that make this inadvisable, and on a fuel injected bike the engine may crank without the fuel system enabled. Treat the result as information about the starter circuit only. Do not condemn the relay before checking these The heavy cables and their terminals. Voltage drop test each one. A corroded cable end produces identical symptoms. The ground path. Starter case back to battery negative. Include it in every voltage drop check. The battery under load. A battery that collapses while cranking makes a healthy relay chatter. See the clicking guide. The engine turning freely. A seized engine will not crank no matter what the electrics do. Specifications you need to look up for your bike Value Why you need it Where to find it Starter relay coil resistance Judging test three Factory service manual Wiring diagram and relay pinout Knowing which small wire is the feed Factory service manual Starter current draw specification Judging whether a starter is overloading the relay Factory service manual Starter and relay terminal torque Refitting heavy cables safely Factory service manual Relay fuse rating Replacing a fuse correctly Owner's manual and the fuse box lid Terminal torque matters more here than people expect. A loose heavy cable terminal is a resistance point that will burn, and an overtightened one strips a soft brass stud. When to stop and take it to a shop Stop if the engine will not turn over by hand. Stop if a cable or terminal shows heat damage, discolouration or melted insulation, because that circuit has been carrying current it should not have and the cause needs finding. Stop if you are not confident about working around a high current terminal, since this is the one circuit on a motorcycle where a slipped tool produces an immediate and serious result. Related checks It clicks but will not crank No crank and no click at all Multimeter basics and voltage drop Back to the full no-start guide Frequently asked questions How do I know if it is the starter relay or the starter motor? Measure across the relay's two large terminals while the starter is pressed. A small drop means the relay is passing current and the fault is downstream in the cable, the starter or its ground. A large drop means the relay is not passing current and the relay itself has failed. Why does my starter relay click but the engine does not turn? The click proves the coil works. It proves nothing about the contacts. Burnt contacts, a weak battery that collapses under load, a corroded heavy cable or a bad ground all produce a click with no cranking, and voltage drop testing separates them. Can I replace a motorcycle starter relay myself? On most machines it is a straightforward job: disconnect the battery negative first, note which heavy cable goes where, swap the unit and refit. The parts that need care are getting the cables back on the correct terminals and tightening them to the specified torque rather than by feel. Is it safe to bridge the starter relay terminals with a screwdriver? It works and it carries real risk. Expect a substantial arc, use a heavy insulated tool, make sure the bike is in neutral, and keep it away from anything flammable. The voltage drop test gives you the same answer without the spark, so use the jumper only if you have a reason to. My relay buzzes rather than clicking once. What does that mean? Buzzing or chattering is the relay opening and closing rapidly, because voltage collapses each time it closes and recovers when it opens. That points at the battery or a connection that cannot deliver current, rather than at the relay itself. About this guide Published by MotoGearRater. Universal procedure only, with no model-specific specifications. Not reviewed by a qualified motorcycle technician, and we say so rather than implying a review that has not happened. Read our editorial standards.

A parasitic draw is current the bike consumes while switched off. You measure it by putting a multimeter in series with the battery's negative cable so every milliamp of standing current flows through the meter, waiting for the electronics to go to sleep, then pulling fuses one at a time until the reading drops. The drop tells you which circuit is guilty. Difficulty Time DIY cost Tools Safety Level 3, intermediate 45 to 90 minutes, mostly waiting $0 if you own a meter Multimeter with a 10A jack, spanners, fuse puller Meter fuse, battery gas, do not crank Read this before you connect anything This is the one test on the site where getting the meter setup wrong has an immediate cost. Three rules, and none of them are optional. Start on the meter's high current jack. Move the red lead to the socket marked 10A or 20A and set the dial to the matching DC current range. Both jacks are fused, but the volts and ohms jack is usually protected at only a few hundred milliamps, so any surge through it blows that fuse. The 10A jack is the one rated to survive the connection. Never press the starter while the meter is in series. A starter draws hundreds of amps. It will blow the meter's internal fuse instantly, and on a cheap meter it can do worse. Turn the ignition off and leave it off for the whole test. Never connect an ammeter across the battery terminals. In current mode the meter is close to a short circuit. Placed across a battery it will pass an enormous current. The meter goes in the circuit, in line with a cable, not across the battery. Also the usual battery precautions: ventilate the area, eye protection, no sparks near the battery, remove rings and metal watch straps, and do not lay tools on the battery. Step one, prepare the bike Charge the battery fully first. A flat battery makes every reading suspect. Ignition off, key out, all lights and accessories off. Close whatever the bike considers closed. Some machines keep circuits awake while a seat, a pannier or an ignition barrel cover is open. Have the fuse box open and accessible before you start, with the lid legend visible, because you will be pulling fuses without disturbing the meter connection. Step two, put the meter in series Set the meter to DC current on the 10A range, red lead in the 10A jack. Loosen and remove the negative cable from the battery's negative terminal. Negative first, always. Touch one meter probe to the battery negative post and the other to the disconnected negative cable end. All the bike's standing current now flows through the meter. Keep that connection stable. If it breaks, some modules wake up and you have to start the wait again. A crocodile clip lead pair makes this far easier than holding probes, because the next step involves waiting and then working on the fuse box without disturbing anything. Step three, wait for the bike to go to sleep This is the step most people skip and it is the reason most parasitic draw tests give a false result. When you first connect, the reading will be higher than the true standing draw because modules, clocks and instrument panels are awake. They shut down on a timer. Watch the display and wait for it to settle to a low, stable figure. On a simple older machine that may be almost immediate. On a modern bike with engine management, an immobiliser and an instrument cluster it can take several minutes or longer. Do not draw a conclusion until the number stops falling. Then change range, or you will get a false pass. The 10A range protects the meter, but on a typical meter it resolves only to hundredths of an amp, which is ten milliamps per digit. A real standing draw is often just a few milliamps, so on the 10A range a genuine fault can read 0.00 and look like nothing at all. Once the reading has settled and is clearly well under an amp, bridge the meter with a jumper lead so the circuit is never broken, move the red lead to the milliamp jack, select the milliamp range, then remove the jumper. If you simply unplug the meter to change range, the electronics wake up and the wait starts again. Step four, read the result A motorcycle with a clock, an immobiliser or engine management will always have some standing draw. That is normal and by design. What matters is whether yours is within the figure your manufacturer specifies. We are not going to print a milliamp threshold here, because the acceptable maximum is model-specific and publishing a generic number is exactly how riders end up replacing healthy parts. The specification lives in your factory service manual. What you can judge without it is the shape of the result: a draw large enough to flatten a healthy battery in days is a real fault, and a draw that does not settle at all is a real fault. A rough sanity check you can do arithmetically: divide your battery's capacity in amp hours by the draw you measured in amps, and you get a very approximate number of hours before it is exhausted. That calculation ignores the fact that a battery is effectively dead well before it is fully discharged, so treat it as a rough order of magnitude and not a prediction. Step five, find the circuit by pulling fuses With the meter still connected and settled, pull one fuse at a time, watch the reading, then put it back before moving to the next. When the reading drops significantly, the circuit protected by that fuse contains your draw. Note that on some machines pulling certain fuses wakes other modules, which can briefly raise the reading. Let it settle again. If no fuse changes anything, the draw is on an unfused circuit or upstream of the fuse box. Aftermarket accessories wired directly to the battery are the classic case, and the first place worth looking. Once you have the circuit, the fuse box legend and the wiring diagram in the service manual tell you what is on it. Then it becomes a matter of disconnecting components on that circuit one at a time until the draw disappears. What is usually guilty In practice, aftermarket wiring is the most productive place to look. Alarms, heated grip controllers, USB sockets, auxiliary lighting, satnav mounts and trackers are all commonly wired to a permanent live rather than a switched one. A previous owner's installation, done quickly with a scotch lock, is a strong candidate on a used machine. Chafed wiring touching frame is the other frequent finding, particularly where a loom passes a sharp edge or a steering head. Specifications you need to look up for your bike Value Why you need it Where to find it Maximum acceptable standing current draw Deciding whether your reading is a fault Factory service manual Sleep time for the electronics Knowing how long to wait. Rarely published, so wait until the reading stops falling and stays stable Factory service manual Wiring diagram and fuse allocation Identifying what sits on the guilty circuit Factory service manual, and the fuse box lid Battery capacity in amp hours The rough time-to-flat sanity check Owner's manual, or the battery label When to stop and take it to a shop Stop if you find damaged or chafed wiring inside a main loom, because a poor harness repair is a fire risk. Stop if the draw is coming from an engine management module or an immobiliser, since diagnosing those usually needs manufacturer software. And stop if the draw disappears and returns intermittently, because intermittent electrical faults consume enormous amounts of time and a workshop with a wiring diagram and proper probes will find it faster. Related checks Why the battery keeps going flat Multimeter basics, including current mode Testing the charging system Back to the full no-start guide Frequently asked questions How much parasitic draw is normal on a motorcycle? It varies enormously between a simple carburetted machine with no electronics and a modern bike with engine management, an immobiliser and a clock. Because of that, the only honest answer is the figure your manufacturer specifies for your model. We deliberately do not publish a generic number, because riders use generic numbers to condemn healthy parts. Why did my meter go blank during the test? You almost certainly blew its internal fuse, most often by leaving the meter in series while something drew heavy current, or by having the leads in the wrong sockets. Most meters have a replaceable fuse behind the back cover. Check the leads are in the 10A jack before you reconnect. Can I do this test with the meter on the positive side? Electrically it works, since the same current flows through the whole circuit. Working on the negative side is safer, because if a probe slips against the frame on the negative side nothing dramatic happens, whereas a slip on the positive side is a direct short. The draw is fine but the battery still goes flat. What now? Then the battery is not holding charge or the charging system is not replenishing it. Disconnect the battery entirely, charge it, and see whether it holds overnight on the bench. If it does, test the charging system. If it does not, the battery is finished. Do I have to disconnect the battery to fit an accessory safely? Disconnecting the battery before wiring anything is good practice regardless. More importantly, wire accessories through a switched supply or a relay triggered by a switched supply, rather than directly to a permanent live. That single habit prevents most of the draws described on this page. About this guide Published by MotoGearRater. Universal procedure only, with no model-specific specifications. Not reviewed by a qualified motorcycle technician, and we say so rather than implying a review that has not happened. Read our editorial standards.

Test a charging system in one fixed order: battery first, then charging voltage at the battery, then stator output, then the regulator rectifier. Skipping to the end is why riders replace regulators that were never faulty. Each step tells you whether the next one is worth doing. Difficulty Time DIY cost Tools Safety Level 3, intermediate 45 to 90 minutes $0 if you own a meter Multimeter with AC and DC volts Running engine, hot exhaust, drive chain Before you touch anything Several of these tests need the engine running with panels removed. Keep meter leads, sleeves and fingers away from the drive chain or belt, the cooling fan, and the exhaust. Support the bike properly, transmission in neutral. Do not run an engine in an enclosed space. Stator output measured with the plug disconnected is live alternating current at a much higher voltage than the battery, so read the warning in step four before you probe it. One rule specific to charging systems: never disconnect the battery while the engine is running in order to see whether the bike keeps going. It is an old test from a different era of vehicle electrics, and on a modern machine it can destroy the regulator rectifier and other electronics. Every test below is done with the battery connected. Step one, the battery, because everything else depends on it A charging system test performed on a flat or failing battery gives misleading results throughout. Charge fully, let it rest a few hours, and measure resting voltage across the terminals. For a conventional or AGM 12 volt lead-acid battery, roughly 12.6 to 12.8 volts is full, around 12.4 volts is roughly three quarters, and below 12.0 volts is deeply discharged. Those are chemistry figures, not model figures. Lithium iron phosphate batteries read differently, so use the maker's published figures for those. If the battery will not hold charge overnight on the bench, disconnected from the bike, replace it before going any further. See why the battery keeps going flat. Step two, charging voltage at the battery This is the headline test and it takes thirty seconds. Meter on DC volts, probes across the battery terminals, engine started, revs raised off idle and held steady. Result Meaning Next step Voltage rises clearly above resting, typically into the region of 13.5 to 14.5 volts, and holds Consistent with a working charging system, but confirm against your model's specified figure before closing the case Check the service manual target, then look elsewhere: a parasitic draw or a tired battery Voltage stays at or below resting voltage Not charging. The bike is running off the battery Go to step three Voltage climbs well above about 15 volts Overcharging. This boils batteries and can damage electronics Stop riding it. Go to the regulator rectifier Voltage wanders up and down erratically Intermittent connection, failing regulator, or a partially failed stator Check connectors first, then steps three and four Between about 14.5 and 15 volts is a grey band where plenty of healthy systems sit, particularly with a cold battery, so do not act on a reading in that range without checking your model's figure. The 13.5 to 14.5 volt range is a general expectation for a healthy 12 volt system, not a pass mark for your machine. Your model has a specified charging voltage and a specified engine speed at which to measure it, and those live in the factory service manual. Use them to judge a borderline result. Step three, check the connectors before condemning parts Do this before any component test, because it is free and it is frequently the answer. The connector between the stator and the regulator rectifier carries real current and is a known heat point on many machines. Unplug it and look at both halves. Discolouration, melted plastic, greened or blackened pins, or a pin that has receded into the housing are all findings. Check the regulator's ground and its output wiring to the battery for corrosion. Use voltage drop testing along the charging output path with the engine running, exactly as described in the multimeter guide. A connection losing voltage under load is a fault whether or not the components either side of it are healthy. A burnt connector will make a perfectly good stator and a perfectly good regulator behave like failed ones. Replace the connector properly rather than reassembling it and hoping. Step four, the stator The stator is the generating half of the system. It produces alternating current, which the regulator rectifier then converts and controls. Two tests apply, one with the engine running and one with it stopped, and both are covered in detail in how to test a motorcycle stator. One safety point before you do it: unloaded stator output is far higher than battery voltage. Tens of volts at idle and well over a hundred volts at raised rpm is normal on many machines, so set a manual-ranging meter to its highest AC volts range first, hold the probes by their insulated bodies, and keep the disconnected plug halves from touching each other or the frame. In summary: with the stator unplugged from the regulator and the engine running, measure AC volts between each pair of stator output leads. The readings should be present, should rise with engine speed, and should be reasonably similar to one another across the pairs. With the engine off, measure resistance between each pair of leads, which should be low and similar, and, on a three-phase stator, measure from each lead to the engine case, which should show no continuity at all. Continuity to the case there means a winding has shorted to it and the stator has failed. Check the wiring diagram first, because some single-phase systems and some separate lighting coils ground one lead by design, and on those a continuity reading is normal. The actual voltage and resistance figures your stator should produce are model-specific. We do not publish them. Compare your readings against the factory service manual for your machine. Step five, the regulator rectifier Only reach this step once the battery, the connectors and the stator have been cleared, because a regulator is often blamed for their failures. Testing it is covered in how to test a motorcycle regulator rectifier. The short version: if the stator produces good AC output and the connectors are sound, but DC voltage at the battery does not rise with engine speed, the regulator rectifier is the remaining suspect. If voltage climbs above roughly 15 volts, the regulating function has failed and the unit needs replacing before it destroys the battery. Specifications you need to look up for your bike Value Why you need it Where to find it Charging voltage target, and the rpm to measure it at Judging step two properly Factory service manual Stator AC output voltage at a stated rpm Judging step four Factory service manual Stator coil resistance between phases Static stator test Factory service manual Regulator rectifier test values Judging step five Factory service manual Wiring diagram for the charging circuit Identifying which wire is which Factory service manual Every figure in that table is a number we will not guess at. Charging system specifications differ substantially between machines, and a value taken from a forum post about a different model is worse than no value at all. When to stop and take it to a shop Stop if you find melted wiring or a burnt connector inside a main loom rather than at a serviceable plug. Stop if charging voltage is above roughly 15 volts and do not keep riding, because you are cooking the battery and stressing everything else. Stop if the stator has failed on a machine where the stator sits behind the engine side cover, unless you are equipped to drain the relevant fluid and work inside the case, since that job needs a torque specification and a new gasket. Related checks Testing the stator Testing the regulator rectifier Battery keeps going flat Back to the full no-start guide Frequently asked questions What should a motorcycle charging system read at the battery? A healthy 12 volt system typically shows a clear rise above resting voltage once the engine is running above idle, commonly somewhere in the region of 13.5 to 14.5 volts. Your model has a specific target and a specific rpm to measure at, and a borderline reading should be judged against that figure rather than against a general range. Is it the stator or the regulator? Test the stator first, because it is the input. If the stator produces healthy AC output and the connectors are clean, but the battery is not receiving DC, the regulator is the remaining candidate. Doing it the other way round is how people buy regulators they did not need. Can I test the charging system without starting the engine? Partly. You can measure battery resting voltage, stator resistance and stator continuity to ground with the engine off, and those three catch a lot. Charging voltage and stator AC output need the engine running, because the system only generates when the crankshaft turns. Why did my new regulator fail too? Usually because the underlying cause was never fixed. A burnt connector, a poor ground, or a partially shorted stator will destroy a replacement regulator as readily as it destroyed the first one. Check the connector and the stator before fitting a new unit. My voltage reads fine at high rpm but the battery still goes flat. Why? Because a system can produce enough at high rpm and not enough in the riding you actually do. Repeated short trips, heavy accessory loads and a lot of idling can all leave a bike in net discharge with a technically functioning charging system. Also rule out a parasitic draw, which drains the battery while the bike is parked and is invisible to a running test. About this guide Published by MotoGearRater. Universal procedure only, with no model-specific specifications. Not reviewed by a qualified motorcycle technician, and we say so rather than implying a review that has not happened. Read our editorial standards.

A battery that keeps going flat has one of three causes and you can separate them in an afternoon. Either the battery is worn out and no longer holds charge, or something is draining it while the bike is parked, or the charging system is not putting back what the bike uses. Test in that order, because each result decides whether the next test is worth doing. Difficulty Time DIY cost Tools Safety Level 2 to 3, some experience helps 1 to 3 hours across a couple of sessions $0 to diagnose with a meter you own Multimeter, battery charger Battery gas and acid, running engine Before you touch anything Charge the battery fully before starting. Every measurement below is meaningless on a flat battery, and you will condemn innocent parts. Ventilate the space, keep sparks away from the battery while it charges, and wear eye protection near the terminals. Some of the tests below need the engine running. Keep hands, sleeves and meter leads away from the drive chain or belt, the cooling fan and hot exhaust, and do not run an engine in an enclosed space. Test one, is the battery still any good Charge fully, then let the bike sit untouched for a few hours so the surface charge dissipates. Measure resting voltage across the terminals. Resting voltage State of charge 12.6 to 12.8 volts Full About 12.4 volts Roughly three quarters About 12.2 volts Roughly half Below 12.0 volts Deeply discharged These are lead-acid figures, applicable to conventional and AGM motorcycle batteries. Lithium iron phosphate batteries do not follow this pattern and should be judged against the maker's figures. Now the important part. A battery that will not hold a full charge overnight after being charged, with nothing connected to it, is finished. Disconnect it from the bike entirely, charge it, leave it on the bench and measure again the next day. If it has fallen significantly on its own, the battery is the fault and no further testing on the motorcycle is needed. Age matters here. Lead-acid motorcycle batteries have a finite service life, and one that has been deeply discharged several times will be well short of its original capacity. If yours is old and has been run flat repeatedly, the honest answer is often that it has simply reached the end. Test two, is something draining it while parked If the battery holds charge on the bench but goes flat on the bike, something on the bike is drawing current with the ignition off. That is a parasitic draw, and it is measured with the meter in series so all the standing current flows through it. The full procedure, including the important safety points about using the meter's high current jack and never cranking the engine with the meter in series, is in how to test for a parasitic draw on a motorcycle. Read that page before attempting it, because getting it wrong blows the meter's internal fuse at best. Common culprits worth suspecting first: an aftermarket alarm, a fitted accessory such as a heated grip controller or a satnav mount, an aftermarket USB charger wired direct to the battery rather than to a switched supply, and a chafed wire touching the frame. Fitted extras are far more often the cause than original equipment. Test three, is the charging system replacing what you use If the battery is sound and there is no significant standing draw, the bike is not putting charge back. This is the test that catches a failing stator or regulator before it strands you. Measure DC volts across the battery terminals with the engine running and the revs raised off idle. On a healthy system you will typically see somewhere in the region of 13.5 to 14.5 volts, higher than the resting voltage because the system is actively charging. The exact target figure and the rpm at which to measure it are specifications for your model, published in the factory service manual, so use those rather than treating the range above as a pass mark. What you measure at raised rpm What it points at Voltage rises above resting into the charging range and holds steady The charging system is working. Go back to test one and two Voltage stays at or drops below resting voltage Not charging. Suspect stator, regulator rectifier, wiring or connectors Voltage climbs well above about 15 volts Overcharging. Stop riding it. This destroys batteries and can damage electronics Between about 14.5 and 15 volts is a grey band. Plenty of healthy systems sit there, particularly with a cold battery, so check your model's specified figure before acting on a reading in that range. Work through the full sequence in how to test a motorcycle charging system, which then splits into testing the stator and testing the regulator rectifier. The cause that is not a fault at all Short journeys. Starting an engine takes a large amount of charge out of a battery, and a charging system needs running time to put it back. A machine used for repeated very short trips, particularly with heated kit or auxiliary lights running, can end up in a slow net discharge with nothing broken. If that describes your riding, a battery tender used between rides solves it, and no parts need replacing. Cold weather compounds this. Battery capacity falls as temperature drops while the current needed to crank a cold engine rises, so a marginal battery that coped in summer gives up in winter. Specifications you need to look up for your bike Value Why you need it Where to find it Charging voltage target and the rpm to measure at Judging test three properly Factory service manual Maximum acceptable parasitic draw Judging test two Factory service manual Stator output voltage at rpm Judging the stator Factory service manual Stator coil resistance Static stator testing Factory service manual Battery type and capacity Correct replacement Owner's manual, or the battery label When to stop and take it to a shop Stop if the battery case is swollen, hot, leaking or smells strongly of sulphur, which suggests it has been overcharged. Stop if charging voltage is above roughly 15 volts, and do not keep riding, because you will destroy the new battery and possibly more. Stop if you find melted or discoloured wiring near the regulator or its connector, since those connectors carry real current and are a known heat point on many machines. Related checks Testing for a parasitic draw Testing the charging system in the right order A new battery and it still will not start Back to the full no-start guide Frequently asked questions Why does my motorcycle battery keep dying overnight? Overnight is fast, which points at a significant parasitic draw or a battery with an internal fault rather than at a marginal charging system. Disconnect the battery overnight and see whether it survives. If it does, the drain is on the bike. If it does not, the battery is finished. How long should a motorcycle battery last? There is no single figure, because it depends on climate, use pattern, how often it has been run flat and whether it has been kept charged over winter. What is reliable is the behaviour: a battery that no longer holds charge on the bench, disconnected from the bike, has reached the end regardless of its age. Will a battery tender fix this? A tender fixes the short-journey case and protects a battery over winter storage. It does not fix a parasitic draw, a failed stator or a dead cell, it only masks them. If you need the tender every few days on a bike you ride regularly, something is wrong and the tender is hiding it. Can I test the charging system by disconnecting the battery while it runs? No. That is an old trick from a different era of vehicle electrics and it can destroy the regulator rectifier and other electronics on a modern machine. Measure voltage at the battery with everything connected instead. My voltage reads 12.5 volts with the engine running. Is that charging? No. If the running voltage is not clearly above the resting voltage, the system is not charging and the bike is running off the battery. Expect a healthy system to sit meaningfully above resting voltage at raised rpm, and check your model's specified figure to confirm. About this guide Published by MotoGearRater. Universal procedure only, with no model-specific specifications. Not reviewed by a qualified motorcycle technician, and we say so rather than implying a review that has not happened. Read our editorial standards.

A new battery that will not start the bike usually means the battery was never the fault, or the new battery was never properly charged before fitting. Both are common. Before buying anything else, confirm the battery is actually full, confirm the connections are clean and tight, and confirm the charging system is not about to kill this battery too. Difficulty Time DIY cost Tools Safety Level 2, easy DIY 30 to 60 minutes $0 to diagnose Multimeter, spanners, battery charger Battery gas and acid, high current Before you touch anything You are about to work on battery terminals and then deliberately draw heavy current through them. Both deserve care. Lead-acid batteries vent hydrogen, which is explosive. Ventilate the space and keep sparks and flames away from the battery. Eye protection near the terminals. Battery acid causes serious burns. Remove rings and any metal watch strap. A ring bridging a terminal to the frame causes severe burns. Disconnect the negative cable first and reconnect it last, so a slipped spanner cannot short the positive to the frame. Do not lay tools on top of the battery. Transmission in neutral and the bike supported before any test that could crank the engine, and do not run an engine in an enclosed space. The first thing to check is the new battery itself A new battery is not necessarily a charged battery. Batteries sold off the shelf have been sitting, and they self-discharge while they sit. A battery that leaves the shop at a partial state of charge will crank weakly or not at all, and it gets blamed on the bike. Measure the resting voltage across the terminals with everything switched off. For a conventional or AGM 12 volt lead-acid battery, roughly 12.6 to 12.8 volts is fully charged, around 12.4 volts is roughly three quarters, and below 12.0 volts is deeply discharged. Those figures are properties of the chemistry rather than of your model. Lithium iron phosphate batteries read differently and should be judged against the maker's own published figures. If it is not full, charge it fully on a proper battery charger before you conclude anything. Charging it by riding is a poor substitute, particularly on a machine whose charging system may already be suspect. Second, was the battery prepared correctly Conventional batteries supplied dry with a separate acid pack need to be filled and given an initial charge before first use. Skipping or rushing that step permanently reduces the battery's capacity. If your battery came with an acid pack and you filled it and fitted it straight away, it may already be underperforming. Also check that you fitted the right battery. Physical fit is not the same as electrical fit. A battery with a lower capacity than the machine calls for will crank a cold engine poorly even when it is brand new and perfectly healthy. Third, the connections This is where a great many of these cases end. A new battery is often fitted onto the same tired terminals and the same corroded ground strap that were there before. Remove both cable ends and look at the mating faces. Clean bright metal on both sides, not grey powder or green crust. Tighten the terminal bolts properly. A finger-tight terminal will pass enough current for the dash and not enough for a starter. Check the ground strap between engine and frame, and between frame and battery negative. Corrosion under a bolt head is invisible until you undo it. Confirm polarity. It happens, and on a fuel injected machine reversed polarity can damage electronics. Then measure rather than trust your eyes. Voltage drop testing while the starter is pressed will show you exactly which connection is losing the current. Widely used workshop rules of thumb are under about 0.2 volts across a cable or connection and under about 0.1 volts across a ground. The method is in how to use a multimeter on a motorcycle, and the full sequence is in the clicking guide. Fourth, find out what killed the old battery This is the step riders skip, and it is why some people fit two or three batteries in a season. If something on the bike destroyed the last battery, it is already working on this one. Three things on the bike can kill a battery, and each has its own page. The charging system is not replacing what the bike uses. Test it. Engine running at raised rpm, a healthy system typically shows somewhere in the region of 13.5 to 14.5 volts at the battery, but the exact target is a specification for your model. See how to test a motorcycle charging system. Something is draining it while parked. An accessory, a clock, an alarm, a chafed wire. See how to test for a parasitic draw. The charging system is overcharging. A failed regulator can push voltage high enough to cook a battery in weeks. Anything much above about 15 volts at the battery with the engine running deserves immediate investigation. See testing the regulator rectifier. Fifth, if the battery is genuinely fine, the fault is elsewhere Once you have a fully charged, correctly specified battery on clean connections, and the charging system is behaving, the no-start is not a battery problem and never was. Go back to the branch that matches the symptom. It cranks but does not fire: fuel, spark, compression and air. It clicks and will not crank: the clicking guide. Nothing at all happens: no crank and no click. Specifications you need to look up for your bike Value Why you need it Where to find it Correct battery type, group size and capacity Confirming the new battery is the right one Owner's manual Charging voltage target at rpm Judging the charging system properly Factory service manual Maximum acceptable parasitic draw Judging a standing drain measurement Factory service manual Minimum cranking voltage Judging a load test Factory service manual Battery terminal torque Tightening without stripping a soft terminal Factory service manual When to stop and take it to a shop Stop if the battery case is swollen, hot, leaking or smells strongly of sulphur, and dispose of it properly rather than continuing to test it. Stop if the charging voltage is above roughly 15 volts, since continuing to ride will destroy the new battery and may damage other electronics. And stop if you have fitted two batteries in quick succession without finding a cause, because the cause is on the bike and it is worth paying someone to find it. Related checks Back to the full no-start guide Why the battery keeps going flat Testing the charging system Multimeter basics and voltage drop Frequently asked questions Do new motorcycle batteries need charging before use? Very often, yes. Batteries self-discharge on the shelf, and many are supplied at less than full charge. A conventional battery supplied dry with acid also needs an initial charge after filling. Fitting a partly charged battery and blaming the bike is one of the most common mistakes in this whole area. My new battery reads 12.8 volts but the bike still will not crank. Now what? Resting voltage only tells you state of charge. Watch the meter while the starter is pressed. If voltage holds and the starter does nothing, current is not reaching it, so test the cables, the relay and the grounds. If voltage collapses hard, the battery may be full but faulty, or a connection is choking the current. Can a bad regulator rectifier kill a new battery? Yes, in both directions. A regulator that fails to charge lets the battery drain until it is damaged. A regulator that fails to regulate overcharges and boils it. Either way the battery is the casualty and not the cause, which is why testing the charging system before fitting the second battery saves money. Is it worth buying a lithium battery instead? Lithium iron phosphate batteries are lighter and hold charge well while standing, but they behave differently in cold weather, they need a charger suited to the chemistry, and some older charging systems are not ideal for them. If you fit one, use the battery maker's own voltage figures rather than lead-acid figures, because the numbers on this page will mislead you. Could I have simply fitted it backwards? Check. Reversed polarity is not common but it is not rare either, and on a modern machine it can blow a main fuse or damage electronics immediately. If the main fuse blew the instant you connected the battery, that is the first thing to rule out. About this guide Published by MotoGearRater. Universal procedure only, with no model-specific specifications. Not reviewed by a qualified motorcycle technician, and we say so rather than implying a review that has not happened. Read our editorial standards.

Total silence when you press the starter is a different problem from a click. Nothing in the start circuit is energising at all. That points at power reaching the circuit, a blown fuse, a ground, or one of the safety interlock switches that are designed to stop the bike cranking. Most causes here are cheap, and several are free. Difficulty Time DIY cost Tools Safety Level 1 to 2, beginner 20 to 60 minutes $0 to diagnose, fuses are pennies Multimeter, basic spanners, torch Low, but respect the battery Before you touch anything The risk here is lower than on the high current pages, but the battery still deserves respect. Transmission in neutral and the bike properly supported, in case a test succeeds and the engine cranks. Remove rings and any metal watch strap before working near the battery terminals. Eye protection near the battery, and ventilate the space. Lead-acid batteries vent hydrogen, which is explosive. If you disturb a battery cable, disconnect the negative first and reconnect it last. Do not lay tools on top of the battery. Work through this in order. The sequence goes from free to expensive deliberately. Step one, does the bike have power at all Turn the ignition on and look at the dash. What you see What it tells you Dash completely dead, no lights, no needle sweep Power is not reaching the ignition circuit. Battery, main fuse, ignition switch or a main ground Dash lights normally but nothing on the starter Power is fine. The fault is in the start circuit or an interlock Dash lights then dies when you press start Voltage collapsing. Treat this as a weak battery or bad connection and read the clicking guide Step two, the interlocks, because they are free Manufacturers build in switches whose entire job is to prevent the engine cranking in unsafe conditions. Any one of them can fail and produce complete silence. Check all of them before you buy anything. Engine stop or kill switch. Look at it. Work it back and forth several times, since the contacts corrode and a few operations sometimes restore them temporarily, which is itself a useful diagnosis. Neutral switch. Is the neutral light on? If the light is dead but the bike is definitely in neutral, the switch or its wiring is a strong suspect. As a cross check, pull the clutch in fully and try the starter. If it now cranks, the neutral circuit is your fault. Clutch switch. A small plunger switch at the clutch lever. Pull the lever fully to the bar. If it cranks only when the lever is squeezed hard, the switch is out of adjustment or worn. Side stand switch. Retract the stand fully. These switches sit low, take road spray and salt, and fail often. Cycling the stand up and down a few times sometimes restores contact. Starter button. Buttons corrode internally, especially on machines parked outside. Work it repeatedly. A useful pattern: if the bike cranks in one combination of neutral, clutch and stand positions but not another, you have located the failing switch without any test equipment. Step three, fuses Find the fuse box. On most machines it is under the seat or behind a side panel, and the lid usually carries a legend telling you what each fuse protects. Check the main fuse first, then the ignition fuse, then anything labelled for the starter or the engine management. Pull each fuse and look through it rather than judging by eye in place, since a hairline break is easy to miss. Better still, check continuity with a multimeter. Replace only with the same rating printed on the fuse and in the manual. Fitting a higher rated fuse to stop it blowing removes the protection that was doing its job and can start a fire. A fuse that blows again immediately is telling you there is a short. Do not keep feeding it fuses. Find the short. Step four, is the ignition switch passing power With the meter on DC volts, measure at the battery, then measure downstream of the ignition switch with the key on. If full voltage is present at the switch input and little or nothing leaves it, the switch or its connector is the fault. Ignition switch connectors are a common corrosion point on older machines. Step five, grounds Every circuit needs a return path. A main earth strap between engine and frame, or frame and battery negative, that has corroded will produce symptoms across the whole bike, often including complete silence at the starter. Test grounds by voltage drop rather than by resistance. Voltage drop only appears while current is actually flowing, and on a bike that does nothing at all there is no starter current to use, so you have to load the circuit yourself. Switch the headlight to high beam, or hold the horn, then put the meter on DC volts with one probe on the battery negative post and the other on bare metal on the engine case. A widely used workshop rule of thumb is that a good ground loses under about 0.1 volts under load. A high reading means the return path is choked, and a reading of zero with nothing switched on tells you nothing at all. The method is covered step by step in how to use a multimeter on a motorcycle. Step six, the start circuit itself If power is present, fuses are good, interlocks are satisfied and grounds are sound, what remains is the low current side of the start circuit: the starter button, the wiring to the relay, and the relay's own coil. On many machines you can hear and feel the relay click when the coil energises, which is why silence points here. Testing the relay coil and its supply is covered in testing the starter relay and solenoid. Specifications you need to look up for your bike Value Why you need it Where to find it Fuse box location and fuse ratings Checking and replacing fuses correctly Owner's manual, and the fuse box lid Wiring diagram for the start circuit Knowing which wire should be live when Factory service manual Which switches sit in the start circuit, and their expected state Judging a switch test Factory service manual Starter relay coil resistance Judging the coil Factory service manual A wiring diagram is the single most useful document for this fault, and it is the main reason a service manual earns its price on an older machine. When to stop and take it to a shop Stop if the machine has an immobiliser or keyless system and the security indicator is behaving abnormally, since those usually require a dealer diagnostic tool and sometimes a key relearn. Stop if a fuse blows repeatedly and you cannot locate the short. Stop if you find damaged, chafed or melted wiring in a loom, because a harness repair done badly becomes a fire risk. Related checks Testing the starter relay and solenoid Using a multimeter, including voltage drop If it clicks rather than staying silent Back to the full no-start guide Frequently asked questions My dash lights up but nothing happens on the starter. What is that? A lit dash proves the ignition circuit has power, which rules out a lot. The fault is downstream, in the start circuit or an interlock. Work through the kill switch, neutral, clutch and side stand before anything else, because those are free to check and fail often. Can a side stand switch really stop the bike starting? Yes. It is a safety feature, not a fault, and the switch itself is exposed to road salt and spray. On a machine that will not crank with the stand up, try cycling the stand fully down and up several times, then retry. If that changes the behaviour, the switch is the problem. Why does it crank with the clutch pulled in but not in neutral? Because the neutral side of the interlock is failing while the clutch side still works. Most likely the neutral switch, its wiring, or the neutral indicator circuit. The bike is not broken in a dangerous way, but the switch should be repaired rather than worked around permanently. Is it safe to bypass an interlock switch to get home? Bypassing one removes a safety feature that exists to stop a bike lurching forward when started in gear, or riding away with the stand down. As a temporary roadside measure some riders do it. As a permanent fix it is a bad idea, and we would not recommend leaving a machine that way. The main fuse blew. Can I just fit a bigger one? No. The fuse rating is chosen to protect the wiring, and wire that is protected by too large a fuse can overheat before the fuse ever blows. A fuse that blows is reporting a fault. Fit the correct rating and find the cause. About this guide Published by MotoGearRater. Universal procedure only, with no model-specific specifications. Not reviewed by a qualified motorcycle technician, and we say so rather than implying a review that has not happened. Read our editorial standards.