Shim now or shim later

[cadmandu]

Shim thickness from 2.60 to 2.65 = .002

If the required clearance is .03 to .08 mm which is between .001 and .003 why do the shims come in .002 increments?

[mike_of_bbg]

Ummm, because when you get down to the min gap, you put in the next lower size and then you're at/near the max. If you're in spec there's no need to change the shim. If you're out of spec .05mm should get you back in.

When the bikes were made there were "x" sizes, where x is between the printed size and the next size (e.g., 2.70x =~ 2.73mm). Nobody seems to sell those any more.

[Steve]

If the required clearance is .03 to .08 mm which is between .001 and .003 why do the shims come in .002 increments?

Because of the simple math of it all.

If your clearance gets below .001, installing a shim that is .002 thinner will get your clearance back up to just under .003.
If your clearance gets above .003, installing a shim that is .002 thicker will get your clearance back down to just over .001.

Now, before everyone else chimes in here, the shims are marked in METRIC values.
They do not come in .002 increments, they come in .05mm increments.
It makes it MUCH easier to also measure in metric values so you don't confuse the issue.
What confusion, you say? Minimum clearance is 0.03mm, maximum clearance is 0.003". Have you every lost or inserted an extra zero?

Nah, me neither.

.

[AirCooledFour]

Shim Math

Ummm, because when you get down to the min gap, you put in the next lower size and then you're at/near the max. If you're in spec there's no need to change the shim. If you're out of spec .05mm should get you back in.

When the bikes were made there were "x" sizes, where x is between the printed size and the next size (e.g., 2.70x =~ 2.73mm). Nobody seems to sell those any more.

So if I buy a 29.5 - 29.45, this is a .05 shim? I'm horrible at math!

[cadmandu]

.05mm is equal to .0019"

Is this not correct?

[Wallowgreen]

So if I buy a 29.5 - 29.45, this is a .05 shim? I'm horrible at math!

Hmmm.... I think you may be getting a little confused here bloke. There are two dimensions you need to worry about, the diameter and the thickness. One at a time...

The diameter you need is 29.5mm nothing else. If you get in there and find you have some 29.0mm shims fitted, take them out and replace them even if the clearance is correct. At high revs they can be thrown out the bucket and have a great time bouncing around boogering everything up.

The thickness is the number everyone's talking about the math on. In metric (which is real money of course ) they step in increments of 0.05mm. So for example a 2.80 shim is 2.80mm thick. Next size up is called 2.85 and is... yes you've guessed it... 2.85mm thick. Only other thing is sometimes the thickness is referred to without the decimal point so 2.80mm shim can be noted as 280.

Hope that helps.

[AirCooledFour]

Thank you!

Hmmm.... I think you may be getting a little confused here bloke. There are two dimensions you need to worry about, the diameter and the thickness. One at a time...

The diameter you need is 29.5mm nothing else. If you get in there and find you have some 29.0mm shims fitted, take them out and replace them even if the clearance is correct. At high revs they can be thrown out the bucket and have a great time bouncing around boogering everything up.

The thickness is the number everyone's talking about the math on. In metric (which is real money of course ) they step in increments of 0.05mm. So for example a 2.80 shim is 2.80mm thick. Next size up is called 2.85 and is... yes you've guessed it... 2.85mm thick. Only other thing is sometimes the thickness is referred to without the decimal point so 2.80mm shim can be noted as 280.

Hope that helps.

Thank you very much, it helps a lot!!

[BassCliff]

.05mm is equal to .0019" Is this not correct?

Hi,

Technically, yes. There are metric equivalents for Standard American measurements and vice-versa.

Personally, in order to avoid confusion, since mine is a metric bike, I use metric tools and metric measurements. I know a lot of folks use nothing but .001" to .003" when spec-ing their valves, but when in Rome....


Thank you for your indulgence,

BassCliff

[Steve]

Hmmm.... I think you may be getting a little confused here bloke. There are two dimensions you need to worry about, the diameter and the thickness. One at a time...

The diameter you need is 29.5mm nothing else. If you get in there and find you have some 29.0mm shims fitted, take them out and replace them even if the clearance is correct.

You may think, "what's the big deal, there's no chance of that happening". WRONG.

Kawasakis and some Yamahas use 29.0mm diameter shims. If the bike was ever taken to a dealer that handled either of those two makes, there is a remote chance that the wrong shims had been installed. Worse yet, if a previous owner had either of those two bikes, there is a better chance that the wrong shims were installed.

A couple members here have recently reported doing their first valve adjustment and found multiple 29.0mm diameter shims in their bike, forcing them to buy more shims than they would have otherwise needed.

.