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changing shims is not a pure science...

  • Thread starter Thread starter vtskier
  • Start date Start date
V

vtskier

Guest
One would think that if the gap is .03 and you decrease the shim size by .05mm that the new gap would be .08. This is not the case on my bike? I had to jump down two sizes to get a .05 clearance.

Do others find this too? Weird!

By the way, the zip tie method works beautifully!
 
Hmmm yes, i found this too.
What is the zip tie method?

Xxx
 
vtskier said:
One would think that if the gap is .03 and you decrease the shim size by .05mm that the new gap would be .08. This is not the case on my bike? I had to jump down two sizes to get a .05 clearance.

Do others find this too? Weird!

By the way, the zip tie method works beautifully!
Click to expand...

Are you sure you are measuring correctly? You must go exactly by the book or you will get wrong measurements.

Did you measure the shims or just go by what is says on the back? Shims are not always what they say they are. I've been caught on that one.
 
Not an exact science is a very appropriate description. Some times it takes a few shims to get your gap to be correct. I also found this to be true, but..think of the extra shims you'll have laying around for next time!
 
vtskier said:
One would think that if the gap is .03 and you decrease the shim size by .05mm that the new gap would be .08. This is not the case on my bike? I had to jump down two sizes to get a .05 clearance.

Do others find this too? Weird!

By the way, the zip tie method works beautifully!
Click to expand...

Something is wrong if you are seeing so much difference.

Did you rotate the engine a couple of turns after installing the new shim to make sure it's fully seated in the bucket? Are you using the Suzuki instructions on how to position the camshafts before measuring? Another thing, using a tie wrap may dislodge a piece of carbon, trapping it between the valve and seat, and skew the clearance reading on subsequent checks. Not saying a tie wrap is bad, just that there may be some short term consequence.

Another thing to be aware of is the shims themselves vary. Suzuki labels the "thick" shims with an X after the number. For example, a 2.55X is thicker than a 2.55. Aftermarket shims don't have the same marks though. When changing shims I like to measure the old shim first using a micrometer, then hand select the new shim after measuring my stock of possible replacements. I've found that shims vary up to .025mm so it's best to account for that variation (if you have the correct tools).
 
It might not be pure science, but it is basic math.
Something doesn't sound right...
 
Last edited:
1_v8_merc said:
It might not be pure science, but it is basic math.
Something doesn't sound right...
Click to expand...

I thought the same thing when I first starting re-checking, only to find out, the oil film was causing my inconsistency, make sure you properly seat them by rotating them by hand a couple revolutions as stated earlier. You may have even mis-read them at first due to oil on the shim.
 
Thanks for all the responses. I will rotate the engine a few times and recheck.
 
I don't know what the other guys (and gals) do, but after changing shims, I will push the starter button for about 5 seconds. This will turn the engine enough for the cams to press the shims into place a dozen times or so.
Then I will line up the cams properly and check clearances (and record them in that handy spreadsheet that some guy offers).
down2.gif


.
 
Last edited:
hi all...
Maybe im being a bit blonde but i still dont get exactly what the zip tie is doing...
Is it just showing that the piston has risen to its fullest extent or is it being pushed under the valve head?

Please enlighten me oh wise ones from the West.

Xxx
 
The zip tie method is a way to hold the valves open without the special tool. The zip tie goes between the seat and the valve to hold the valve open while changing shims. Ray
 
Seana23 said:
hi all...
Maybe im being a bit blonde but i still dont get exactly what the zip tie is doing...
Is it just showing that the piston has risen to its fullest extent or is it being pushed under the valve head?

Please enlighten me oh wise ones from the West.

Xxx
Click to expand...
We don't really care about your hair color, just ask the question. :rolleyes:

I though I had saved a neat little diagram showing a zip-tie in use, but will have to settle with giving you the link to The Zip-Tie Supplement that is found in Mr. BassCliff's "little" library.

In a nutshell, you rotate the engine so the cam is fully opening the desired valve. If you look through the spark plug hole, you can see the edge of the valve sticking down. Insert the folded end of a zip-tie under the edge of the valve, rotate the crank a full turn to get the cam lobe pointing away from the valve. The valve is being held slightly open by the zip-tie, giving you the clearance that you need to reach in and pull the shim. when the new shim is in place (make sure it's FULLY in place), rotate the engine one turn so the cam is pushing on the valve again, pull the zip-tie, move to the next valve.

A word of caution for those who, like me, are too cheap to throw anything away. :eek:
Yeah, zip-ties are relatively cheap, but I keep mine for several adjustment sessions. Because of the 'victims' I find while out on my travels, I have done DOZENS of valve adjustments. I have found that a folded zip-tie only lasts for about 5 or 6 full inventorying sessions before breaking. Because I also use shrink wrap around the zip-tie to keep it folded, no pieces fall into the cylinder. Note also that an "inventorying session" involves doing EVERY valve to be able to pull the shim, read the value and enter it into my spreadsheet. If shims need to be moved around, the zip-tie is used a few more times that session. On subsequent adjustment sessions on the same bike, you would only need to use the zip-tie on a few (if any) valves, not all of them, so it would last longer.

.
 
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