Hi- Have an '87 yfm225 Moto 4- Great old bike that my kids really enjoy. It was smoking badly, so I had a shop do piston, rings, valve seals, gaskets, etc- complete top end rebuild. The old piston was pretty bad, rings were frozen-- When they put it back together, they couldn't get it to start. They said it kept 'jumping time'. They would reset the timimg and then it would 'jump'. They said that the chain was jumping on the cam shaft (lower) gear. Anyway- It was going to be an arm and a leg to have them tear into the lower engine, so I paid the bill and brought it home. Before taking it in, the thing ran quite well--just smoked like a mosquito fogger-- Now it won't even start-- Any thoughts as to why it will no longer stay in time??

Brad