You hear grinding, crunching or a high screech when you press start, or just after the engine fires. The starter turns the engine through a set of small gears and a one-way starter clutch. Grinding means teeth are not meshing properly, or the starter clutch is slipping or not freeing itself. The timing of the noise is the main clue.
Is it safe to ride?
Yes, carefully, if the engine runs normally and the noise stops at once. If the noise continues while the engine runs, or the starter keeps turning, stop the engine with the key and go to Starter keeps turning after I let go of the button.
Quick checks first
- Does the noise come while cranking, or only after the engine fires?
- Does it stop the moment you release the button?
- Are the starter mounting bolts tight?
- Is the battery fully charged?
Diagnose it step by step
1Does the noise continue after you release the button, while the engine runs?
- Yes: the starter is still being driven or is not disengaging. Switch off with the key. Go to step 5.
- No: go to step 2.
2Is the noise a short screech or bang just as the engine fires, sometimes with a kick?
- Yes: the engine may be firing too early or backfiring against the starter. See Pops or bangs when trying to start and Ignition timing suspected wrong.
- No, it grinds all the time while cranking: go to step 3.
3Are the starter mounting bolts tight and is the starter fully seated?
- No: tighten to your manual's value. K-Light 125: starter mounting bolts 10 to 12 N·m. A loose starter lets its gear jump teeth.
- Yes: go to step 4.
4Remove the starter. Are its gear teeth chipped, rounded or worn on one side?
- Yes: the gear it drives is probably damaged too. Remove and inspect the starter motor, then have the idle gears checked.
- No: the starter clutch or idle gear is the likely source. Check the starter clutch.
5Does the starter keep spinning with the button released?
- Yes: the relay contacts may be welded or the button stuck. Test the starter relay.
- No, the motor stops but a screech continues with the engine running: the starter clutch is dragging. Check the starter clutch.
What happens if you ignore it: broken gear teeth can fall into the engine and cause much bigger damage.
Causes, most likely first
| Cause | How to confirm | Fix |
|---|---|---|
| Loose starter motor | Bolts loose; starter moves by hand | Tighten to the manual value |
| Worn starter clutch | Slips then grabs; screech on start | Check the starter clutch |
| Damaged starter or idle gear teeth | Chipped teeth when starter is removed | Remove and inspect the starter motor |
| Engine kicking back at start | Bang or kick as it fires | Check the ignition timing |
| Starter not disengaging | Noise continues after release | Test the starter relay |
Reference values (K-Light 125)
| Item | Value | PDF page |
|---|---|---|
| Starter motor mounting bolts | 10 to 12 N·m | 92 |