Help with Shim Puzzle

[Norseman]

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.


Norseman

[robertbarr]

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?

[tomcat24551]

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.

[Norseman]

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

[Steve]

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.


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[robertbarr]

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.

[Norseman]

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.

Now I have to revisit the strategy...

Norseman