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YZ250 Puking oil


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I've been doing some hillclimbs on my 03 YZ250, and I noticed there's oil all over the crankcase halves after a few climbs.

I noticed this problem when I first got the bike, but it was coming out the crankcase vent hole on the left side of the bike which didn't have a tube attached. I installed a breather hose, and routed it up and over the air boot so oil doesn't spill out when climbing now, but I'm still seeing oil from somewhere else. Last weekend the right half (clutch side) was covered in oil. The oil filler cap was tightened and forms a good seal. The cover for the powervalve assembly on the right side may not be sealing well but I don't think its bad enough to let oil out like I'm seeing.

Is anyone else having this problem with their YZ on hillclimbs? The only other thing I can think of is that the gasket between the case halves is bad, or the case halves aren't aren't torqued properly.

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I very rarely do hill climbs but in the few Ive done Ive never had any problems with oil leaking. It could be that somethings not torqued right but does this only happen on hill climbs, or does it always leak? Possibilty youre putting too much oil in your bike? Could be the base gasket but I very highly doubt it if your not having any problems with jetting. This would cause mixture issues as well, so my guess would be that the bad seal is ruled out.

Also should mention that my buddy has a YZ that leaks oil from the vent hole even though theres a hose on it, it just doesnt seem to fit tightly enough to stop the oil from pushing through the connection once the bike warms up and the oil gets thin.

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I was doing serious technical rocky climbs and after I saw a lot of gearbox oil on the clutch side. Turns out its from the o ring seal on the power valve actuator arm which comes through the engine case, Replaced it and its been good ever since,

by the way its the same size as the one at the top of the powervalve linkage going into the cylinder head

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