The left cover usually covers the generator and the right cover the clutch, oil pump and often a centrifugal oil filter. Oil can leak at the gasket between cover and crankcase, round the shafts that pass through the cover (kickstart, gear lever, clutch lever) or through a crack from a fall. Covers are aluminium; loose screws and a gasket that has aged or been pinched are the common causes. Overfilled oil and a blocked breather raise the pressure inside and make small weak spots leak.
Is it safe to ride?
Yes with care for a seep. Do not ride if oil is running, the cover is cracked, or oil reaches the tyre or brake.
Quick checks first
- Has the bike been dropped on that side? Look for scrapes and cracks.
- Is the oil level above the upper mark?
- Is the leak at the cover edge or round a shaft?
- Was the cover recently removed for a repair?
Diagnose it step by step
1Clean and find the exact point with Trace an oil leak. Is it from a crack in the cover?
- Yes: the cover needs replacing or welding by a workshop. A crack from a fall can grow fast. See The bike has been dropped or crashed.
- No: go to step 2.
2Is it round a shaft (kickstart, gear lever, clutch arm)?
- Yes: it is the shaft seal, not the gasket. Ask a workshop to replace the seal; the gear lever seal can usually be done without opening the case. Check the lever is not bent and pushing the shaft sideways.
- No, along the cover edge: go to step 3.
3Is the oil level above the upper mark, or is the breather blocked?
- Yes: correct the level with Check the engine oil level and clear the breather with Check the crankcase breather. Clean and recheck.
- No: go to step 4.
4Are any cover screws loose? Check each by hand with the correct tool.
- Yes: snug loose screws gently to the manual torque (K-Light 125: crankcase cover bolts 9.8 to 11 N·m). Do not overtighten; aluminium threads strip. Clean and recheck after a ride.
- No, all tight: go to step 5.
5Was the cover off recently?
- Yes: the gasket may be pinched or the wrong one. Return to the person who did the work.
- No: the gasket has aged. Ask for Replace an engine cover gasket.
Causes, most likely first
| Cause | How to confirm | Fix |
|---|---|---|
| Overfilled oil or blocked breather | Level, hose check | Check the crankcase breather |
| Loose cover screws | Screw turns | Snug to manual torque |
| Aged or pinched gasket | Wet line along the joint | Replace an engine cover gasket |
| Shaft seal | Wet round a shaft | Workshop seal replacement |
| Cracked cover | Visible crack after a fall | Replace cover |
Reference values (K-Light 125)
| Item | Value | PDF page |
|---|---|---|
| Left and right crankcase cover bolts | 9.8 to 11 N·m | 194 |