Valve Shims - Stamped Size vs. Actual Measured Thickness

[FJ1100mjk]

Hello, and Happy New Year (or thereabouts):

I'm in the process of checking the valve clearances on my '87, and found myself needing to adjust a few of them. While in the process of removing the existing shims I noted that some of them were lacking any identification number, or the one that existed was illegible. When I ran across this problem, I brought out my trusty Harbor Freight measuring device (digital caliper) to measure their thicknesses. I know that I should be using a outside micrometer for a more trustworthy measurement of the shims, but feel that based upon the feel and look of the shims, that there doesn't exist enough wear on the shims that if using a set of digital calipers instead of an outside micrometer will throw off my measurements that much. I know that the digital calipers are measuring very closely, because the shims' OD's are measuring very close to 25mm, or spot-on to that value.

Problems/discrepencies exist between what I'm finding when I perform measurements of the shims, and what I am finding on their stamped ID numbers. I'm under the impression that their stamped number is their thickness in millimeters moved two decimal places over (i.e. 280 = 2.80mm thick). However, I am finding conflicting values such as a used shim stamped 285 that measures 2.71mm. And there's a number of these used shims that are having this issue, but they don't show any outward/evident signs of wear.

I've measured all of the valve clearances and cataloged their values. My next step will be to remove each shim and measure it, so I know the "real" size of the shim, and then use that value as to what should be the stamped size, then order a new shim based upon the thickness that is required to get the correct valve clearance.

Can one (or more) of the FJ sages tell me if the above makes sense, or you've run across the same experiences when doing your valve clearances, and if I am approaching the problem and solution correctly?

I don't mean to open another can of worms, but should I also compensate for the lack of an oil film that will now be missing since I am cleaning it off the shims when I'm making my measurements? Such as subtracting one or two thousandths of an inch off of the new needed shim size because in the actual running of the engine, the oil film will compensate for the extra clearance, and be correct at that point? Maybe it's so close anyways, so that it doesn't matter, but I thought that I'd throw it out for opinions before I order the shims.

Thanks in advance.
Marty

[FJmonkey]

Having only done my vales once I will offer what I can on this.
Using calipers is a rough means of measuring your shims. Not only because they will only measure the highest spots along the surface of the shim but also because of a lack of finer graduation that micrometers provide. If your shims are not visibly worn then you are likely getting about +/- 1/2 MM. This should get you close to a decent valve adjustment. Don't compensate for oil film thickness, that is already factored in. Make sure your engine is at ambient temperature, not hot or really cold (30 F). I found that the oil does affect measuring clearance just after putting a shim in. I chose to insert the new size shim, turn the motor so the cam is pushing the valve down and let it sit for a few sips of beer. This will push some of the oil out of the seat before I check the new clearance. Once the engine is back together and running the shims fully seat and clearances change again but this is why there are tolerances. Getting your clearances within tolerance is all you need to do. FWIW, I do not have a collection of shims so I needed to chose between a tight valve and a loose one. My #1 intake valve is a tappy (happy) valve till next adjustment.

[FJ111200]

That different measurement in the shim from 285 to 271 says one thing to me, and that the shim has been ground down on a surface grinder to the required size.
It's a common enough occurence. I run a "shim library" on the UK XS1100 forum and have come across this sort of thing on XS shims, but never on a FJ shim, though it must exist,  even though i've got about 60 each of both types of shim.
There also seems to be an argument for not grinding the shims to fit, as some say it takes away the case hardening. I've used and are using ground down shims in my XS's without any problems so far, fingers crossed.
But i suppose just for safety's sake you are wise to get a un-molested   shim.
I do things as an experiment just to see sometimes, so you takes your chances.

[FJmonkey]

There also seems to be an argument for not grinding the shims to fit, as some say it takes away the case hardening.

If one must grind, then remove material from the seat side, not the cam side... Plus it removes the now incorrect size etched on it. Might be good to scribe that side to keep it identified for seat side.

[racerrad8]

I've measured all of the valve clearances and cataloged their values. My next step will be to remove each shim and measure it, so I know the "real" size of the shim, and then use that value as to what should be the stamped size, then order a new shim based upon the thickness that is required to get the correct valve clearance.

Thanks in advance.
Marty

Marty, that is the best way to do it. As already mentioned the common practice years ago was to "grind" the shim to obtain the correct lash. And since the lash always gets tighter you can continually grind the same shim and never have to buy a replacement.

This was done primarily based on cost. Before there were aftermarket shims available, Yamaha was charging almost $20.00 a shim. I know because I bought some back in 94 and could not believe the price. At that time I found a tool that was made to hold the shim so that they could be ground on a valve machine, you can still get it today too.

Now that you have determined the shims have in fact been ground then you need to do it exactly as you explained above. If you remove the shim and reinstall them, the oil "film" between the bucket & shim must be pushed out. Mark gave an example of what he does, which I have never tried, but I might for next time. I always run the engine to temp so the oil is hot and then let it cool back down, that ensure the oil is out and the shim is properly seated as well.

If you are talking about the film of oil when measure the shim outside of the engine, they should be wiped clean prior to measuring.

I throw all "ground" or modified shims in the garbage and install the proper thickness shim into all engines. This save the owner to ton of grief, much like you are experiencing now.

You can find all of you shim needs from 230 -320 right here;  
http://rpmracingca.com/proddetail.asp?prod=Head%3AVs

Randy - RPM



[edit] fixed link.

[simi_ed]

 

Randy, you are such a help! 

[FJ1100mjk]

Guys:

Thanks a lot for all of the feedback and insight. Much appreciated.

Looks like I will be ordering the correct shims to properly baseline my valve clearances.

Happy New Year
Marty

[Mark Olson]

Marty ,

most of the time you will end up moving the shims around between the different valves and only end up needing 2 or 3 shims.

loose is better than tight on the fj engine , cause if you run it hard they get tight and burn valves. 

use a micrometer to measure the shims accurately as the calipers only hit the high spots. 

[FJ1100mjk]

Mark:

I just spent a few hours going over the valves in both of my FJ's. I set them up for shimming on the loose side as you advise.

Happy New Year.
Marty

[Horse]

I measure each shim 3 times  & then get someone else to do it as well... Never trust anything when it comes to shims !!!!! they are $2.00 each exchange here in the big OZ...