yes, it does it after it warms up, but not as often. no, i have no idea what type of pistons they are, is there any way to tell? I alwaya warm it up properly, however i cant say for the guy who owned it before me. when i do ride it i always let it idle until it is too hot to put my hand directly on the head. can i pull the head and jugs and have them mic'd to see what the clearances are, or do i just need to say, f$$k it and have it redone. I'd rather just drop 250 on a bore job than break a shirt and end up buying a top and bottom end.