Have a 2004 yz450 and noticed oil being used at a much greater rate than say 6 weeks ago. No smoking, can't find a leak anywhere, and the bike hauls total ass. There is however a noticeable amount of air being blown out of the crankcase vent hose. But again no oil leaking here either. A thin film of oil is present at the tip of the hose, but i assume that is from the condensation of crankcase oil vapors. This airstream does seem to increase in pressure with higher revs. Deep down i think it may be the oil or a compression ring going out on the piston. Say it ain't so!