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Help with Shim Puzzle

  • Thread starter Thread starter Norseman
  • Start date Start date
N

Norseman

Guest
Ok, I just can't seem to wrap my mind around what shims I need to buy, and what shims I can swap. I thought I had it, but when I tried, my clearance went way high (>1mm).

So I thought maybe if I posted my worksheet, some of you may be so used to this you could quickly suggest a strategy. I know this is simple, but it seems I get lost between measured clearance at .0xx and translating it to the shim metrics. Appreciate any help by you gurus that have done this before.
ValveClearance040107.jpg


Norseman
 
It's been a long time since I've done this! In fact, I've forgotten what the IN/EX clearance specs are. Got'em handy?

It's curious that nearly all ofyour measurements are 0.03 or so higher than nominal... I'd be suspicious of the measured shim thicknesses. Maybe try a different instrument?
 
What kind of bike are we talking about here?

Usually the 8 valve bikes call for clearances between .03mm and .08mm COLD. I guess some could be different from this spec, but I don't know which ones.

Your "gauge clearances" are ALL measured in mm, too, right? If they aren't, you will get confused, so try to get them all measured in mm.
 
Specs

Specs

Sorry, I always forget to mention it's a GS650GLX. I am staying strictly metric, using an electronic caliper I just bought. According to Clymer, the clearance spec is .03 - .08, if I understood your question correctly.

I agree with your skepticism about the actual shim metrics, Robert. The shims appear to be factory, and my understanding was those are usually right on. I have a calibrated micrometer, and I am going to do a comparative measurement right now. The occasional "flyer" can be probable, but every one?

In fact, I'll use the micrometer on three and see what I get...

Norseman
 
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Are your clearance measurements in inches or millimeters?

If they are mm, #1&2 exhaust are right on. If they are in inches, they are WAY too loose.

I started to do an Excel spreadsheet to help me with this a couple of years ago. I got stuck doing some of the automatic calculations, but I can give it another try in the next couple of days.


.
 
Well, for starters -- you'll need to acquire a pair of 2.60's (maybe even go with 2.55's) for 1E and 2E. No way around that. Use the discard 2.65 in 2I and 4I (assuming you have a placeholder shim) to get those measurements. Possibly (probably?) the 2.65's will bump those clearances up to spec.

Looks like you'll get away with acquiring only two shims.
 
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Adjusted Measurements

Adjusted Measurements

Robert,

You were absolutely correct - my fancy electronic caliper is way off. I measured all 8 shims with first the caliper, then a micrometer. The yellow column is the micrometer metrics for the column to its left. As you can see, your skepticism was justified.
ValveClearance040107B.jpg

Now I have to revisit the strategy...

Norseman
 
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