Bike died at the track few weekends ago. Came out of a corner and just died. It did start up after but sounded awful, so I killed it and put in a new top end. Again, Bike started up, but still sounds bad, almost like a deep echo coming from in the engine. Took the cylinder off and found this oily residue on the new piston. Oil looked kind of milky and didn't really have a distinct smell. Also I’ll lost a picture of the piston that came out after it died, which looks like lots of blow-by. Complete engine rebuild had 16 hours on it. All seals and bearings replaced. Cylinder has not been replated or conditioned for as long as I've had it. Ring gap checked good but that's all I checked.
I’m thinking now possibly warped head and that antifreeze mixed with premix on the piston... or possibly bad right side crank seal and it’s tranny oil.
Any suggestions? Bike is a 05 YZ250.
