small valve shim

11 replies to this topic
  • bigthump426

Posted April 05, 2013 - 07:43 PM


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

  • grayracer513

Posted April 06, 2013 - 09:29 AM


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.

  • bigthump426

Posted April 06, 2013 - 04:00 PM


So what am I looking to get reseated

  • grayracer513

Posted April 06, 2013 - 06:59 PM


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.

  • bigthump426

Posted April 06, 2013 - 09:17 PM


Yeah I think all the valves need re seating the biggest shims I have is 1.50 on the exhaust side I have 1.20 and 1.30 on the intake side

  • cmgyz450fs77

Posted April 08, 2013 - 03:25 PM


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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  • grayracer513

Posted April 08, 2013 - 03:52 PM


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.

  • bigthump426

Posted April 08, 2013 - 06:53 PM


Ya I have Ti valves so not doin that so if its just needs reseated probably won't be an arm and a leg

  • grayracer513

Posted April 09, 2013 - 06:17 AM


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.

  • bigthump426

Posted April 09, 2013 - 09:34 AM


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

  • grayracer513

Posted April 09, 2013 - 03:36 PM


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.

  • bigthump426

Posted April 09, 2013 - 04:54 PM


Ok thanks grey

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