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spc mike

another valve clearance question on 426 ...

7 posts in this topic

i checked my valves about 10 min ago because i wasnt to assured that i did it right last time and iam going to pismo for spring break and i want it to be in top operating order, but on the intake side i measured .102 mm...and i know thats almost to the edge of its acceptable range(.10-.15) But my question is do you think they would of been around that range from the factory?(currently still factory shims in my bike) and would you reccomend going down a shim size to get near the middle of the reccomended range? if i went down a shim it would be 185's for all three intake's...and thats coming down from a 190,190,189 size shims currently. so pretty much what would you guys reccomend? :thumbsup:

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... on the intake side i measured .102 mm...
Then you should leave them alone. The specification states that if a valve has clearance between .10-.15mm, it is as it should be. That includes valves that have either .10 or .15mm exactly, too.

For one thing, our English unit minds get far to wrapped up in the whole thing without realizing that the total tolerance range of .05mm is not quite .002" (0.00196"). The middle of that is only 1 thousandth of an inch different from either end.

And for another, the reason you found them both that way is more than likely because that's exactly where they were set when they left the factory. Yamaha deliberately sets up the valve clearance as near the low end of the tolerance as they can to improve the operation of the valve train, even using shims in .01mm increments to do it. Your bike is fine. Cover it back up and give it a hug.

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its a little off subject, but since this post was involving valves, i just figured id throw my question in.

did any of the yz400f or yz426f come with titanium valves in them?

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its a little off subject, but since this post was involving valves, i just figured id throw my question in.

did any of the yz400f or yz426f come with titanium valves in them?

98-00 models had SS valves from the factory, 2001-2008 have Ti valves.

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