Posts
19
Joined
3/4/2018
Location
Middleburg, FL
US
Edited Date/Time
5/17/2018 10:39am
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.
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.
The Shop
You could also have it checked with a bore gauge to ensure the bore is straight and circle, not oval.
How about up and down play in the crank?
You said the bike was rebuilt, but not the crank?
If the crank gets loose, it will take out the right crank seal. Loose crank can be growly/echo and possibly vibration.
If you inspect the right side crank seal from behind the clutch cover, check that the primary drive gear is still held on tight by the bolt.
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