Sportbike chain clunks or jerks: chain slack and wear
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Applies to: Aprilia RS 660 and Tuono, Triumph Speed Triple and all chain-drive bikes
Symptoms
- Clunk when getting on and off the throttle
- Chain slaps the swingarm
- Tight and loose spots as you turn the wheel
Why it happens
Chains stretch and wear unevenly, and slack outside spec makes the drive jerky and wears sprockets. Too tight is just as bad for bearings.
How to fix it
- Measure slack at the midpoint with the bike positioned as the manual says.
- Find the tightest spot and adjust there.
- Align the rear wheel using the adjuster marks.
- Replace chain and sprockets together if stretched or hooked.
Tools and parts
- Rear stand
- Torque wrench
- Chain lube
What the factory service manual covers
Final drive: chain slack spec, wear limit, axle torque. The full procedure, specs and wiring diagrams are in the factory service manual for your machine.