Valve Shim Thickness

[79GS850]

Hi All!

I'm baffled.

I've started the valve adjustment on my 850 and I'm confused about the shim thickness. So far I've pulled, measured and re-installed each shim. Good practice!

I'm working with Steve's spreadsheet. (Helps tremendously!)

Some of the shims still had the size marked on them and others were a blank.

Now here's where I'm mystified.

A marked 2.70 shim measures 2.68 for example.

Unmarked shims read 2.79 2.78 2.72 etc. Math nightmare?

Should I work with the actual measurements or round up or down to 2.80 or 2.75 etc.?

Also, initially I'm working with a feeler gauge that goes down to .038mm and then jumps to .05 something. I should get my Snap On gauge tomorrow. Then I can get the accurate clearances.

I'd like to end up as close as possible to .08mm.

[BassCliff]

Greetings and Salutations!

Hi Mr. 79GS850,

It's always a good idea to measure the shims, whether they are marked or not. The 2.79 shim would probably have been marked 2.80. The 2.72 shim would probably have been marked 2.70x, the "x" meaning oversized.

With odd sized shims you can really dial in your clearances. It's OK to run them even a little looser. Some of my exhaust clearances are .09mm - .1mm.

I think you can plug in the actual numbers and let Mr. Steve's spreadsheet do the math. It sounds like you are doing good work so far. Feel free to check out the valve clearance guide on my website for more information. Now let me roll out the welcome mat for you...

Please click here for your mega-welcome, chock full of tips, suggestions, links to vendors, and other information. Then feel free to visit my little BikeCliff website where I've been collecting the wisdom of this generous community. Don't forget, we like pictures! Not you, your bike!

Thanks for joining us. Keep us informed.

Thank you for your indulgence,

BassCliff

[Steve]

It is also good to make sure that your caliper gets re-zeroed every once in a while.

I agree that the 2.72 is probably a 2.70x shim, but enter it as a 2.72 on the spreadsheet. I have found that most of the X shims are just about half-way between the full-numbered sizes, and the spreadsheet does not know what to do with an alpha character when adding or subtracting, so just enter any X shim as the number plus .02. Enter that 2.72 shim as a 2.72. If your clearance is tight on that one, it will suggest a 2.77, so you will have to evaluate whether you actually have a 2.75x shim or if a 2.75 will do the job. The spreadsheet helps a lot, but you still have to do a little bit of thinking. If you stay consistent with that entry system, you will see that all your standard shims will have numbers ending in 5 or 0, and all your X shims will have numbers ending in 2 or 7.

.

[tfb]

I always err on the side of wider clearances, because valve clearances will close with time. Also, from what I can tell you get a bit better low-end power with clearances which are at the wider end of the stipulated range.

[Dre]

It is also good to make sure that your caliper gets re-zeroed every once in a while.

.

+1 on that, "Wow, this float is way off... Wait I forgot to zero it."

[79GS850]

Thanks for the replies!

Steve and BassCliff, you two have been a great help even before answering my post.

BassCliff- I've been all over your site. I even printed a couple of pages from your valve adjustment pdf. and had them in the garage for guidance. Steve- Your spreadsheet helps keep all the #'s in order.

I was better at English...YOU do the math.

Stay tuned...

Oh! I did zero the calipers. Brand new set. I zeroed before each measurement. Of course, ya gotta allow for that + - variance.