New valves equals new shims but what size?

5 replies to this topic
  • Brett1981

Posted February 16, 2009 - 09:30 PM


I have just replaced the intake valves in my YZ426 00' and now have found out I need new shims. I am wondering if there are any methods to measure what size I need or is it a trial and error thing? The shop told me that I should be able to measure somehow because they want me to swap and pay.

  • matt4x4

Posted February 17, 2009 - 06:43 AM


you really can't just measure, however, you should have some shims kicking around from your bike's previous valves - maybe even just give the smallest shim you have a try, if it fits with room for play so you can measure (even a BIG gap) you can always measure one at a time then calculate what you really need.
should be relatively quick with everything on the bench.

  • marknir

Posted February 17, 2009 - 06:46 AM


If you are doing this on the bench, be very carful or you will bend the new valves.

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  • mike_dean

Posted February 17, 2009 - 06:59 AM


If you are going to be riding and working on these bikes you should invest in a shim kit from HotCams, basically all the big bikes take the same size(9.48) its worth the the investment, check ebay or the HotCams website or TT. Mike

  • Brett1981

Posted February 17, 2009 - 02:10 PM


Thanks, yeah I wish I had the shim kit would save a lot of trips to the shop. But what I will do is as you suggested - put a small shim in and measure the clearance. Maybe a 150 I will start with. I want to sell and update asap.

  • grayracer513

Posted February 17, 2009 - 02:31 PM


If you are careful, you can get close by using a smaller shim and holding the cam down on the head by hand. Seat the ball bearing by tapping it down with a wood or plastic mallet, and hold pressure on the cam as you take your measurement. Saves a bit of time.

If you use a full set of gauges, you should be able to get in the ball park this way.

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