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Valve Leak Down Issue

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Looking for a few opinions in here if you dont mind. I have performed a valve leak down test on my 2011 kx250f and have came up with 40% leakage at TDC, which I can hear coming out of the intake side. Exhaust side is quiet with no leaks. I have also done a cylinder compression test at 75 psi dry. My valve shims are all within spec so my issue is what other damage to the valves could possibly cause the intakes to leak? Next step is to pull the head and valves and eyeball it. Can the valves be shot but still be withing spec? The bike has no trouble starting and has no backfire etc. Opinions please :)

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Yes the valve faces and the valve seats wear with use,

despite the valve to cam clearance being set within the tolerances, the valves still leak due to poor sealing on their seats.

Also meaning you can't simply install a new valve on a worn seat, the seat has to be re-cut. (not lapped)

 

Edited by mlatour
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Sounds like this engine may have been eating dirt.  The intake valves have it pretty good compared to the exhaust as long as all they see is fuel and air.

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