Screamin' Eagle Stage Kits Explained: Stage 1 to 4 Costs, Gains, and the Warranty Truth
- jamesjordan
- 2 hours ago
- 4 min read
Quick answer: Screamin' Eagle stage kits are Harley's factory performance ladder. Stage 1 is intake, exhaust, and a tune. Stage 2 adds cams. Stage 3 adds big bore displacement. Stage 4 adds ported heads and a bigger throttle body. Installed by an authorized dealer, the street legal kits are designed to preserve your factory warranty.
Stage | What it adds | Typical parts cost | Typical gain |
Stage 1 | High flow air cleaner, freer exhaust, ECM tune | About $1,000 to $1,500 | Roughly 5 to 10 percent |
Stage 2 | Performance cam and pushrods (torque or power grind) | About $450 to $550 plus Stage 1 | Up to roughly 15 to 25 percent depending on grind |
Stage 3 | Big bore cylinders, pistons, valve springs, cam | About $1,700 to $1,900 plus supporting parts | Roughly 15 to 39 percent depending on engine |
Stage 4 | Stage 3 plus CNC ported heads and larger throttle body | About $2,200 to $3,800 | Roughly 40 to 52 percent depending on base engine |
How the ladder works
Each stage builds on the one below it. Stage 1 lets the engine breathe and recalibrates fueling, and it is the single best value step for most riders. Stage 2 changes the cam profile, and Harley sells both torque grinds for around town and power grinds for top end. Stage 3 raises displacement with big bore cylinders, taking a Milwaukee-Eight 107 or 114 to 114, 117, 122, or beyond depending on kit and year, and Stage 4 finishes the job with ported heads and a larger throttle body. Labor rises with each rung: Stage 1 is a driveway job for a competent owner, while Stages 3 and 4 are engine work best left to a dealer or specialist, and installed totals can add four figures of labor at the top of the ladder. Costs above are typical published parts figures; get a current quote from your dealer because kit contents and prices change by model year.
The warranty question, answered straight
This is the entire reason the Screamin' Eagle line exists. Harley's position, stated in its own announcements of the current stage kits, is that street legal Screamin' Eagle performance kits installed by an authorized Harley-Davidson dealer do not void the factory or extended service plan coverage. The details that matter:
Dealer installation is the key that keeps warranty coverage intact. A self installed cam or big bore invites a coverage argument you may lose.
Street legal kits (50 state or 49 state compliant parts) are the warranty safe path. Race only parts are exactly that, and warranty coverage on affected components ends with them.
Keep every receipt and work order. Warranty disputes are won with paperwork.
A proper dyno tune with the flash tuner is part of the job, not an optional extra. A mistuned Stage upgrade is how engines get hurt, and heat is the enemy of an air cooled motor running lean.
What we would actually do
Most riders, most bikes: Stage 1 and stop. Best cost per smile on the ladder, and the bike stays dead reliable.
Riders who tour two up or with luggage: Stage 2 torque cam. The midrange gain is where touring engines live.
Power chasers with budget: skip the incremental path and price a Stage 3 or 4 kit as one dealer visit, because doing stages one at a time pays for labor twice.
Buying used: a documented, dealer installed staged bike is nothing to fear. An undocumented home built one prices as a project, not an upgrade.
Which bikes this applies to
Current kits target Milwaukee-Eight touring and Softail models, and the pattern reaches back through Twin Cam bikes with era appropriate parts. We have rated the common candidate bikes: see our Street Glide, Road Glide, Low Rider ST, and Street Bob reviews. Our Milwaukee-Eight engine guide covers what the base engines tolerate happily.
FAQ
Does a Stage 1 void a Harley warranty?
Not when it uses street legal Screamin' Eagle parts installed and tuned by an authorized dealer. Harley states this explicitly in its stage kit announcements. Self installs and race parts are where coverage gets murky.
How much does a Stage 1 cost installed?
Plan on roughly $1,000 to $1,500 in parts plus dealer labor and dyno time, with regional labor rates moving the total. Get a written quote; packages vary by dealer and model.
Is Stage 2 worth it?
If you ride loaded or two up, the torque cam version is the most noticeable seat of the pants upgrade on the ladder. Solo riders happy with their midrange can skip it without regret.
How much horsepower does a Stage 4 add?
Harley's published figures and independent write ups put combined gains in the roughly 40 to 52 percent range over stock depending on the base engine, which is why Stage 4 costs what an entire used Sportster does.
Do stage kits hurt reliability?
Street legal kits, dealer installed and properly tuned, are engineered within factory tolerances and warranted accordingly. The reliability risk in staged bikes comes from bad tunes, mixed parts, and undocumented home assembly, not from the kits themselves.
Can I do the stages out of order?
Stage 1 underpins everything, and cams before breathing is money wasted. If you know you want big power, buy the ladder in one step; it is cheaper than climbing it rung by rung.
Sources
Last updated: August 22, 2026. MotoGearRater is independent. We do not sell parts or installs and nobody pays for a recommendation.
