250r fried piston????

joe22883 · #1 (**permalink**) 02-09-2007

I ended up talking to the kid i bought my R of off last night and he finally told me why he got rid of the bike he said he only got a little rding time in on a new top end before he fried it again.So my question is why would that happen? On the flange on the exhaust where it connects is missing a nut somebody stripped it right off by either over tightening or tryin to take it off but it doesnt seem to be leaking out of there although he said when he was riding he had some shit pooling up on him in front of the frame there and he could never figure out what it was.I havent got enough time on the bike yet to really see yet cause its too damn cold here. So what should i check to make sure this wont happen to me? I just finished the new top end and have only rode it mayeb an hour so far...

joe22883 · #2 (**permalink**) 02-09-2007

Nobody has any ideas??

carl250r · #3 (**permalink**) 02-09-2007

it could have been bored to tight. that will F up a piston.

it could be to lean. read about how to do a plug chop. learn about reading your spark plug. so you can tune your carburetor. if it is needed.

joe22883 · #4 (**permalink**) 02-09-2007

yea the top end he did the piston did have some uneven wear.My machine shop said it could be it was heated up to fast and that was what caused it.

joe22883 · #5 (**permalink**) 02-09-2007

Here is a few pictures of the piston that came out...

BlueDiablo · #6 (**permalink**) 02-09-2007

Mkae sure pictures smaller next time lol. The head may have not been torwued to spec. I dont know why people over look one of the most important steps. A crank seal and ruin a topend so quick also. There alot of factors and the best thing to do is to look at everything closly and make your own educated conclusion.

joe22883 · #7 (**permalink**) 02-09-2007

Yea sorry about that i didnt realize they were so big till i clicked on them myself. The bottom end has all new seals so i knwo its not that. I mean it seems to be running ok right no just bogs from 0 to about 1/8 throttle i just havent had a chance yet to mess with the air screw. I just dont want a brand new top end to go to waste ya know.And he got me a little worried when he told me it was a new top end and blew so quickly.So before i go toolin around on it wanna make sure its 100%. Would it have anything to do where the exhaust flange is? There is a bolt stripped of so there is only 2 bolts holding it on.I dont really see and blow by but then again i have not really rode it since the new top end.

ky 2stroker · #8 (**permalink**) 02-09-2007

looks like the piston started to sieze up. the piston cylinder clearance could be too tight most likely. and it looks like to me where it shows the scuff marks on the exhaust side that it maybe wasnt getting enough oil? what ratio you running and what kind of oil? and also a really lean jetting would cause not enough oil for lubrication.

joe22883 · #9 (**permalink**) 02-09-2007

Well that is the piston i took out.That was from the kid who owned the bike before me.So im not really sure who did the machine work or what ratio mix he was running.Maybe im just being paranoid i just dont wanna ruin a brand new top end.Im going to do a plug chop tomorrow and see what i come up with.