As you let the lever out to pull away, the bike shakes, jerks or bites suddenly instead of taking up the drive smoothly. It can make the bike hard to control at walking speed. Common causes are a sticky lever pivot or cable, which stops you feeding the clutch in smoothly, and loose engine mounts or a worn cush drive, which let the drive line bounce. Inside the clutch, burnt plates, warped steels and notches in the basket slots make the plates catch and release.
Is it safe to ride?
Ride with care. Judder makes slow manoeuvres, hill starts and pulling out with a passenger harder to control.
Quick checks first
- Pull the lever slowly: is it smooth all the way, or does it stick and jump?
- Check the lever pivot for dirt and rust.
- Check chain slack: a very tight or very loose chain can feel like judder.
- Did it start after an oil change or a new clutch?
Diagnose it step by step
1With the engine off, pull and release the lever slowly. Is the movement smooth and even?
- No, it sticks or jumps: clean and grease the pivot, lubricate the cable. Service lever pivots, Lubricate control cables.
- Yes: go to step 2.
2Is the lever free play correct? (K-Light 125: 10 to 15 mm.)
- No: Adjust clutch lever free play.
- Yes: go to step 3.
3Is the chain slack correct and even around the chain, and is the rear free of clunks when rocking the wheel?
- No: Check and adjust chain slack, Chain is tight in some places, or Check the cush drive rubbers.
- Yes: go to step 4.
4Are the engine mounting bolts tight and the rubber bushes (if fitted) in good shape?
- No: Check engine mounting bolts.
- Yes: go to step 5.
5Did the judder start after an oil change, or is the oil old?
- Yes: change to the grade in your manual. Change the engine oil.
- No: go to step 6.
6Does it still judder?
- Yes: the plates are glazed or burnt, the steels are warped, or the basket slots or hub splines are notched. Go to Inspect and replace clutch plates and springs.
Causes, most likely first
| Cause | How to confirm | Fix |
|---|---|---|
| Sticky lever pivot or cable | Lever jumps when pulled slowly | Service lever pivots |
| Wrong free play | Measured at lever tip | Adjust clutch lever free play |
| Chain or cush drive | Uneven slack, play at the sprocket | Check the cush drive rubbers |
| Loose engine mounts | Bolts loose, bushes split | Check engine mounting bolts |
| Oil type or age | Started after oil change | Change the engine oil |
| Glazed plates, warped steels, notched basket | Persists after all the above | Inspect and replace clutch plates and springs |
| Plates fitted wrongly after a clutch job | Judder or slip started after the clutch was opened | Refit plates in the original order. The plate that carries the springs must mesh with the basket, or the springs cannot press the pack evenly. Oil new fibre plates before fitting (see your bike's manual) |
Reference values (K-Light 125)
| Item | Value | Source |
|---|---|---|
| Clutch lever free play | 10 to 15 mm | K-Light 125 manual, PDF p. 69 |