who knows man, you coulda put the piston in backwards for all you know. this stuff is touchy. since its a 125 id just bore it bro. otherwise your going to need a new sleeve and that shit gets pricey. did you atleast coat the cylinder walls with 2 stroke oil when you installed it? did you heat cycle it in the drive way 2 or 3 times bro? i bet you didnt break in that top end right. its a process....lmk when you got the parts for it again i'll help you out.