To measure shims or not.......

Over the weekend I did my top end and re-shimmed my valves for the first time. I was able to use 3 of the 4 stock shims to get my valve clearances within spec. I went to my local dealer to buy a 2.93 mm shim and they stated that they always use an electronic micrometer to measure the thickness of the shim instead of going off of the numbers on the shim. When I did my calculations in my garage, I just used the numbers on the shim to figure out what size I needed. My thoughts were that their micrometer could be off and not calibrated properly and that I would have to use the same micrometer on the shim that I removed to truly be accurate? Keep in mind that this is a dealer that also gave me the wrong size diameter shim when I told them it was for an 07 kx250f.

Long story short, I bought a 2.90 mm shim that my dealer measured it to be 2.87 mm because that was the largest they had in stock. I put everything back together and all valve clearances are within spec so I am not that worried about it. But I am curious to see who else measures them and doesn't go off of the numbers on the shim.

I always measure them. There can be a couple thousandths difference between shims. I measure them and then use the ones that will get me right where I want to be for clearance. Let’s say you are .002 in. too tight. Measure the current shim and then find one in your kit that measures .002 in. less. Install that shim, torque the cap and check it. It should be right on the money. Remember, thinner shim to achieve more clearance and thicker shim to achieve less. Hope this helps. :busted:

I always measure them. There can be a couple thousandths difference between shims. I measure them and then use the ones that will get me right where I want to be for clearance. Let’s say you are .002 in. too tight. Measure the current shim and then find one in your kit that measures .002 in. less. Install that shim, torque the cap and check it. It should be right on the money. Remember, thinner shim to achieve more clearance and thicker shim to achieve less. Hope this helps. :busted:

Thanks, it does help. I guess I just got lucky with not measuring them with my micrometer. Although, I always question the accuracy of an inexpensive tool that measures out to the hundreths of a millimeter!

yep, always measure. you would be surpised how far out some manufacturers are from their printed numbers

Although, I always question the accuracy of an inexpensive tool that measures out to the hundreths of a millimeter!

If you have a cheapie set of calipers then you can measure the same shim over and over...20 times or more. checking your results you can see the variablilty of your calipers. i've found some cheapies very repeatable, maybe slightly off, but very repeatable. so then when you buy new shims use your calipers to measure the new shims. then you know if they fit your needs.

I guess that measuring them is common knowledge. I have been reading about valve shims for awhile now and I can't recall anyone mentioning that the shims should be measured. Thanks for all the replies. :busted:

Thanks, it does help. I guess I just got lucky with not measuring them with my micrometer. Although, I always question the accuracy of an inexpensive tool that measures out to the hundreths of a millimeter!

A normal human hair is about 6/100 of a mm. Just for comparison.

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