I recieved a YFM200 free, it would not start, I fixed the carb ans it started but smoked like a desiel... I took off the head and cylinder to replace rings and change valve guides and seals... while doing the work I thought I would replace the timing gears, chain, and guides... I am down to the lower gear and it appears to be a repss fit on the shaft... anyone know if this is true? If so I am thinking of leaving it and just replacing the upper and chain since I donlt have the cases demated.

 

I found out that it is mated to the crackshaft and to replace it requires the crack to come out and split into sections... I decided against it and put the enign eback together without changing it.