How to Test a Motorcycle Starter Relay and Solenoid

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.