clutch slip
Well, usually clutch slippage is due to worn friction discs or springs that no longer exert enough force. Essentially, when these are worn, you kick the motor over and that torque causes the plates to slip.
Some of this is caused by modern day oil...they have friction modifiers in them to the point where it affects clutch performance. So, as a recommendation, I never use any car motor oil or synthetic oil in these motors....Never. If you suspect that your discs slip because you added synthetic oil or car oil, you can take the plates out and rough them up with 80 grit sandpaper or just replace them.
The other reason they slip is due to increased displacement/compression where the clutch cannot take the sudden torque brought on by kicking the engine. For motors with on this side of the spectrum, it is always best practice to get the piston to just after TDC before each kick. This will not only make your starting easier, but it will reduce the chances of you shearing off the kickstarter shaft, or stripping it.
There is always the chance that the clutch needs to be adjusted too or that the motor was sitting for so long that the plates are corroded and not up to task. If your clutch is slipping with a stock bore, adjust the clutch and if that doesn't work, you need to replace the plates and springs. If you have high compression bbk on the bike, you need to either adjust the clutch or change your kicking habits.
