Which valve shim to use...

2 replies to this topic
  • cereal killer

Posted February 04, 2013 - 03:50 PM


I'm in the middle of a valve adjustment, and I'm wondering about which shim to use when I seem to be in between sizes. I think being on the tight side of "in-spec" is better than loose, but maybe I'm over thinking it.

The valve in question had .087mm clearance (should be .1-.15) and a 182 shim under the bucket (I presume from the factory). The manual says to round the 182 to 180 and then use the chart to find the recommended replacement. It suggests 175.

But when I do the math, this would put me at .157... .007 over spec. Whereas if I used a 180, that should put me at .107. - just barely within the standard clearance.

So should I:
1. Listen to the manual and go slightly looser than the recommended clearance.
2. Use the 180 to stay within the recommended range.
3. Find something else to worry about since we're talking about 100ths of millimetres.

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  • grayracer513

Posted February 04, 2013 - 04:11 PM


First, .007mm is .00027". NO ONE can accurately measure the difference between .157 and .150 with a feeler gauge. I know the gauge says that on it, but really?

Second, tighter is better, and .107 is in spec, so go that way.

In the end, the whole of the specified clearance range, .10-.15mm, is only .002" wide, so more often than not, the concern over which end of it to be closer to is indeed overthinking.

  • cereal killer

Posted February 04, 2013 - 04:23 PM


Thanks Gray!

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