deff the stock piston, i measured it all out. Im not dissapointed that it blew up because of the age i know it was time. Im more dissapointed that i was lied to when i bought the wheeler. The kid told me it had a hotrod crank and port and polish and 240 kit. He lied his ass off. so now that ive got the problem diognosed im goiung through and im gunna build this thing good and fast.