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bigthump426

small valve shim

12 posts in this topic

Have to re shim valves on 2000 yz426 went to the dealer to get a 1.50 he said I was nearing the end is this true or can they go smaller

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I think you can get them down to 1.25 for a Honda , but if the valve has that much wear on it, you're running the risk of snapping one off because of seat scrubbing as the valve closes (flexes the stem) or putting so much wear on the seats the they may need to be replaced.

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Depends on where you go an what needs to be done, but you can figure that replacing (as opposed to just refinishing) each seat will add a low of around $50 to the job.

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id try laping your valves before you have the reseated see if you have any gap i know for your bike in your valve clearence is suppose to be .int0.006-0.008 exh0.010-0.012 id lap your valve see if you can see any gaps where the valve sits in the head are you haveing a compression issue?

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Under no circumstance should you attempt to lap the valves you have in there if they have receded that far. The seats WILL be worn, and lapping a new valve to a worn seat will simply transfer the wear pattern on the seat to your new valve, which is NOT what you want to happen.

BTW, absolutely NEVER lap Ti valves (for those who have them; your 2000 model came with stainless steel valves.

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I don't know why a 2000 model would have Ti valves. They were built with stainless, and the SS valves are a third or less the cost of the '01 Ti valves.

Take the head and your new valves to a competent small engine machinist who is familiar with the YZF and have him decide whether the seats can be refinished or need to be replaced.

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The guy I bought it from put ti valves in it but ok that's what ill do thanks

You can rebuild it wit Ti if you want. I wouldn't if it was mine, simply because they cost more than the stainless ones for the 426. If you rebuild with stainless, be sure you get the springs for the 2000 model and not for the '01-'02.

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