Valve shims on a 82 gs550mz

[Steve]

If you hear ticking, I would be surprised to find out that it's the valves. They usually wear tight, meaning that it will get quieter. If they get too tight, the bike will be harder to start when cold. It will start just fine when warmed up for a bit, but will be a bear to start when cold. Decreased gas mileage could be valves, could be carb adjustment, might just need to adjust the nut that holds the handlebars.

If you don't know when the valves were adjusted last, it's probably past time for them to be adjusted. I think most of the manuals call for either 3,000 or 4,000 miles between adjustments. If you have not had the bike that long, can you guarantee that the previous owner did them? One nice thing is that you are supposed to check the valves that often, but they don't always need to be adjusted. If you keep your bike long enough and follow regular maintenance, you may find that you can extend your intervals, but please don't do that until you have established a pattern.

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[Gumbo76]

You should really check valve clearances and adjust as necessary. If you do have to adjust them, you'll have to resync your carbs.

So adjusting the valve Shim wil require Carb adjustment as well, huh? EEgad! Then I will need the Special Sync Tool to measure the Carb adjustments. Are those expensive?

I guess if I am going to have to adjust the carbs anyway, I might as well upgrade to Pods while I'm at it, and then why not Hollow out the Exhaust too? The Syncing is the only reason I haven't done that yet. Ugh!

thanks for the advice!

-Gumbo

[Griffin]

So adjusting the valve Shim wil require Carb adjustment as well, huh? EEgad! Then I will need the Special Sync Tool to measure the Carb adjustments. Are those expensive?

I guess if I am going to have to adjust the carbs anyway, I might as well upgrade to Pods while I'm at it, and then why not Hollow out the Exhaust too? The Syncing is the only reason I haven't done that yet. Ugh!

thanks for the advice!

-Gumbo

If you aren't looking forward to syncing the carbs, about the last thing you want to do is install pods. The carbs will require rejetting if you do that,a nd lots of fiddling around in all likelihood.

Been there, done that, pain in the ass, went back to stock a couple years later.

[Ghostgs1]

I can't imagine these shims are nitride case hardened, the cost would be too high for mass production. They do appear to be an air hardening type alloy steel such as 4140. This is consistent with the thinning rate I've seen using a lapping machine, removes around .001 inch per hour of process time, whether I've removed .001 or .020. Heat input can lead to cracking in this type of steel, if the surface temp gets up to around 1200 it is very likely. When lapping shims they never get hot enough that you cannot handle them with bare hands, maybe 120 degrees. Ray

Neither will surface grinding if done properly, and heat treatment is not the issue.

Regardless whether lapping or grinding is being used, the nitriding case-hardening process (I'm just assuming here that this is what's being used) can certainly be less than .005 (on each side, of course), which is not out of the theoretical range of alteration required.

Of course if you've done it and it works, the point is moot. Maybe the parts really are just hardened all the way through. Seems unlikely to me, but it's possible.

[Commodus]

I can't imagine these shims are nitride case hardened, the cost would be too high for mass production. They do appear to be an air hardening type alloy steel such as 4140. This is consistent with the thinning rate I've seen using a lapping machine, removes around .001 inch per hour of process time, whether I've removed .001 or .020. Heat input can lead to cracking in this type of steel, if the surface temp gets up to around 1200 it is very likely. When lapping shims they never get hot enough that you cannot handle them with bare hands, maybe 120 degrees. Ray

Nitride case hardening is used for mass production all the time.:

Nitriding, also known as nitridization, is a process which introduces nitrogen into the surface of a material. It is used in metallurgy, for example, for case hardening treatment of predominantly steel but also for titanium, aluminium and molybdenum.
Nitriding is widely used in automotive, mechanical and aeronautical engineering. Typical components receiving this metallurgical process are gears, crankshafts, camshafts, cam followers, valve parts, extruder screws, die-casting tools, forging dies, extrusion dies, injectors and plastic-mould tools.

http://en.wikipedia.org/wiki/Nitriding

And I guarantee you can surface grind any of these materials without cracking them. I do it all the time.

All this being said, however, I have no direct experience with these shims so I will certainly defer to your direct experience.

[zacheriaj]

i think i have to find the shim club and see if anyone will trade me. first i gotta find out what size i have in mine. why are the shims so thick though? thick enough to where there is no space between the shim and the lobe. is it because of something else that is wrong?

[Steve]

i think i have to find the shim club ...

Look just a couple of posts above this one for Ghostgs1. In his sig line, you will find a link to the shim club.

... why are the shims so thick though? thick enough to where there is no space between the shim and the lobe. is it because of something else that is wrong?

They are thick so that they are easy to handle, but they come in different thicknesses. By changing to a shim of a different thickness, you can adjust the clearance between the cam and the shim. The clearance that is specified is there because of the expansion rates of the materials in the head and valves. When they get to operating temperature, there needs to be enough clearance to do the job. Only the engineers that designed the engine know what the operating clearances are, and they don't really matter. What matters is that if we set the clearance to 0.03-0.08mm when the engine is cold, it will be proper when the engine is hot.

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[mike_of_bbg]

why are the shims so thick though? thick enough to where there is no space between the shim and the lobe. is it because of something else that is wrong?

The gap which is supposed to be there is very narrow. The spec for your bike is going to be 0.03-0.08mm. At minimum gap - still within spec, mind you - that's thinner than the foil-like 0.0015" thinnest feeler that you can find in most gauge sets. It's been noted several times that the gap tends to tighten with wear. When you stop to think about it, if your valve is closed, what wear points exist in the valve assembly (open you might see the effects cam lobe wear, if you had some method for measuring the "open-ness" of your valves)? The part of the cam you're measuring against should not be in contact with anything, and thus should never wear. The only parts to wear are the valve faces and valve seats to tighten the gap, and the hardened shims to loosen it. The shim is winning the wear-resistance battle there.

Thinking about it more deeply, the camshaft journals can also wear. With the shafts under downward tension from the chain, that would tend to tighten the gap also.

Nothing is wrong - that's just how it works on this motor.