New valves equals new shims but what size?

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.

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.

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

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

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.

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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