Rebuild Time???????????

99 yz400 here are the sympthoms

high idle, it does not get affected by idle screw

could get it turned on like a two stroke without much effort

smells like its burning oil

after running for a while it started to puff out white smoke out of engine vent hose and afterwards it started to leak a little oil thru the same hose

other than that the bike runs fine but it smells like s**t, high idle but it doesnt semm to have a power loss (not that i would be able to tell the difference i bought it used about three weeks ago and never ridden a 400 before only 250) its just pretty fast.

so is it time to replace piston and rings or it couls be something else :D

Sounds like you need to tear it down and do some work....

You could do some testing (compression/leakdown) without tearing it down just yet. Also, old gas and sitting for a while will produce some of those symptoms (the smell particularly), since you've rode it some, I assume you've been through a tank already though.

rebuild time. My 99 YZ400F did exactly the same things yours is doing & I had to have it rebuilt. $850 bucks later it was fixed

thank you guys i'm tearing it down as we speak :D

here is what i found

piston is good

oil ring is not

oil is not milky however the is no coolant, where did it go?????

so it overheated and fried the ring but where did the coolant go

here is what i found

piston is good

oil ring is not

oil is not milky however the is no coolant, where did it go?????

so it overheated and fried the ring but where did the coolant go

Have you popped open the clutch side of the case?

yes changing water pump seals and shaft they are bad (more like melted and the shaft is f*****d)

the bike was put all back together and i still have little compression however it runs good do i have to wait till the rings seat to do the compression test

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