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coop63

Please! 3rd time request for help!

8 posts in this topic

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!

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Air normally moves in and out of the breather pretty vigorously at idle, but if there's a noticeable increase when you open the throttle then that's probably an indication that your rings are weak. A leak down test is the best way to verify this. Most shops can do one for you pretty inexpensively.

There are really only three ways oil can go missing other than leaking. Rings, valve guide seals, or blowing out the vent hose. You say it doesn't smoke. Maybe. But it doesn't really have to so that it can be seen easily. To use 100cc of oil an hour, you have to burn about 0.00033cc each time the engine fires. That won't make a lot of smoke.

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Thanks a lot gray and brian. I will monitor it and get the leak down test. Dang, i was hoping to invest in a rekluse system. Now it might have to be engine work. :devil:

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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

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!

Valve stem seal leakage? The oil is either leaving out the exhaust , out the valve cover breather, or leaking from the casing. Where else would it go? While you are replacing rings, change the valve stem seals. They are very cheap and they are easy to change with just a valve spring compressor.

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...While you are replacing rings, change the valve stem seals. They are very cheap and they are easy to change with just a valve spring compressor.

Good advice

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@ Bbrown, right if it comes to it, i plan to go through it top to bottom and replace all oil leaking candidates.

Might even go to a big bore kit, but first must do some research on these. Thanks! Will do a leakdown

test today as a diagnostic measure.

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Attempted a leak down test, but every time i connected to compressed air the piston would move and take me off TDC, this opens the exhaust valve and air flows out. Tried everything i could to keep the engine from turning to no avail. How do you get anything useful diagnostically when the piston won't stay at TDC?

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