yz400fmaniac

valves, need help

5 posts in this topic

ok just checked valves on my yz400f all intake valves are at .004, inch or .102mm and all exaust are at .009in or .227mm. in spec on my bike is.

intake: .15mm to .20mm, or .0059 inch to .0079 inch.

exaust: .25mm to .30mm, or .0098 inch to .018 inch. 

so i need to know what shims i need to get my bike in spec thanks.

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You need to take out the shims already installed , there is a bit of a process, plenty of threads on it though.

Most bikes from late 90s to now use the same procedure.

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Find out what shims you have (if the numbers are rubbed off use a caliper/micrometer if you don't have one you can get one at harbor freight for like 10 bucks) and do the math to find the shim that will put you the closest to the middle of the specified range. You will need a smaller shim as that will increase the gap. Shim kits are nice to have but not neccessary if you don't mind going to going to a dealer for the shim you need. Also, atleast on hondas, the hotcams shim kit comes in .05mm or 2 thousandths increments while honda offers shims in .025 increments allowing you to get the valves closer to where you want.

Edited by problem_child
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