Dec 23, 2004
Hey guys, I recently rebuilt my 87(?) YZ250 and after riding it for alittle while it began to blow alot of white smoke and eventually died out. Also right when I started the bike up it started to literally pour oil out of the exhaust. The motor has been bored out pretty far so im not sure if it can be done again. What is something that could have caused this? It also sounded like it was pinging when you rode it right before it died. Is there anyway I can get it running again? The bike ran great for a few days and then this happened. I took the proper break in procedures and assembled everything as the manual said. What happened :(
May 9, 2007
The white smoke was probably steam. That, combined with the pinging, would indicate to me that you blew the head gasket, followed by the engine overheating.

The oil out of the exhaust could either be a lot of build-up from previously being ridden very slowly, and you were riding hard enough to blow it out, or maybe the crank seals are gone.
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