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racer164

08 yz450 larger valve shim

3 posts in this topic

did a freshen up on my 08 yz450 , iver never checked valve clearances , but thought i better while is was there ..

all the valves are within spec but 1 .. one of the outer intake valves needed a larger shim .. how is this possible ?

it had a 1.86mm in there and needs a 1.95-2.00mm to be within spec .. valves dont shrink in length ..

and valve is seating fine ( seals fuel when pouring into intake )

cam isnt worn , bucket isnt mushroomed or top of valve either ..

any ideas?

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Last month Mine had the same issue but measured .35mm. The top of the valve had worn off. Pop it out and one of the good ones, then place on flat surface and compare stem hiegth. If you have the manual I think the measurment for valve stem hiegth is in there. Mine was very obvious .

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ahh thanks for the reply .. yea didnt think they could wear down .. ( before the seats wear in/valve stretches )

bike has about 70 hrs on it .. i will shim it correctly and keep and eye on it. ( as the head is back on and bike running again )

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