Valve Adjustment Shims

[dave]

While my question does apply to the CB1100, it also applies generically to most modern motorcycles sold today. I'm posting my question here because I know we have a lot of very talented, and experienced people who frequent this site, and I am hoping someone can provide some informative feedback.

While performing a valve adjustment on a system that uses the small, metallic shims to achieve the proper clearance, has anyone ever encountered shims that have worn to where the surface that contacts the top of the valve stem is concave (cupped), and therefore is not a parallel surface to the opposite side of the shim?

I believe that I just encountered this condition on my VFR800. I performed all my valve clearance measurements, removed and measured all the shim thicknesses, selected the new (thinner) shims required to achieve the proper clearances, and reassembled everything. Upon remeasuring all the new clearances, I discovered the two exhaust valve clearances that I put .003" thinner shims into did not change at all! I double-checked all my measurements before and after reassembly, and triple checked my math. Even if my math was wrong, I know that the replacement shims were .003: thinner than the shims I removed.

I initially blamed myself for just doing something stupid, but when I did a search on the internet concerning this subject I discovered that I am not the only one who has experienced this problem. I learned that my old shims were most-likely cupped where they contact the valve stem, and when I used my caliper to measure the shim thicknesses (the laser-etched markings were not visible), the flat, parallel edges of my caliper could not provide an accurate measurement. I tossed my old shims into a jar, along with the dozens of other shims I have accumulated over the years, so I can't go back and reexamine them now because I don't know which ones they are.

However, I did just order a point micrometer from Ebay, which will accurately measure the shim thickness, even if they are cupped. As soon as I receive my new micrometer I'll finish my valve adjustments (I've only disassembled the rear cylinder at this time).

If anyone can provide some information on this topic it will not only be valuable to me, but I'm sure there are other members who visit this forum who would find this information helpful

Thank you.

 

[rdprdp01]

When I read your post, here are the thoughts that I had:

The cupped shims could also be caused by a bad spring or a damaged tappet. I defer to the pros on the Forum. Hopefully, I did not embarrass myself with this post. David

 

[Gone in 60]

I got nuthin. If I need a new shim, I order from Amazon (none of the local dealers even know what shims are), check ‘em wirh my Harbor Freight digital micrometer to verify thickness and toss them in. If the final reading is close to what I want I call it good.

I’ve never seen a non-flat shim.

 

[dave]

I got nuthin. If I need a new shim, I order from Amazon (none of the local dealers even know what shims are), check ‘em wirh my Harbor Freight digital micrometer to verify thickness and toss them in. If the final reading is close to what I want I call it good.

I’ve never seen a non-flat shim.

What do you consider "close"? Within the +/- .001 inch tolerance from nominal?

 

[Gone in 60]

I got nuthin. If I need a new shim, I order from Amazon (none of the local dealers even know what shims are), check ‘em wirh my Harbor Freight digital micrometer to verify thickness and toss them in. If the final reading is close to what I want I call it good.

I’ve never seen a non-flat shim.

What do you consider "close"? Within the +/- .001 inch tolerance from nominal?

I'd call .001" a tolerable tolerance. I tend to do the math to put my valves on the slightly loose side, so if the variance is to the tight side, I'll still be happy. 

That being said, I'm currently monitoring valve clearances on six BMWs, my Enfield 650 and my Bonneville (which I just measured and shimmed within a few thousand miles ago).
My NC750X hasn't gotten to a mileage that needs an inspection yet.  I still haven't touched my CB1100, and probably won't.

 

[1973cb750]

shimming can be not fun i always run the bike and let it cool after adjustments made and recheck the clearance before sealing it up always let it cool over night before rechecking also i use after market shims so i always mic the old and the new often when i need .003 i need to use a .004 or .004 to equal the .003 needed nothing is perfect anymore also dirt will take up clearance keep everything sanitary clean like spotless one eyelash will have you chasing your tail most cb1100 require not adjustments even at 100k up to .002 over is ok to tight is a problem even .001 too tight if my spec is like .005 and i see .009 ill leave it be

 

[dave]

shimming can be not fun i always run the bike and let it cool after adjustments made  and recheck the clearance before sealing it up always let it cool over night before rechecking also i use after market shims so i always mic the old and the new often when i need .003 i need to use a .004 or .004 to equal the .003 needed nothing is perfect anymore      also dirt will take up clearance keep everything sanitary clean like spotless one eyelash will have you chasing your tail most cb1100 require not adjustments even at 100k      up to .002 over is ok to tight is a problem even .001 too tight if my spec is like .005 and i see .009 ill leave it be

"i always run the bike and let it cool after adjustments made and recheck the clearance before sealing it up always let it cool over night before rechecking"

Can you please clarify how you do this? You have to "seal it up" before running it, don't you? Are you saying you put everything back together after making adjustments, run the engine, let it cool, then take it completely back apart again?

 

[1973cb750]

shimming can be not fun i always run the bike and let it cool after adjustments made  and recheck the clearance before sealing it up always let it cool over night before rechecking also i use after market shims so i always mic the old and the new often when i need .003 i need to use a .004 or .004 to equal the .003 needed nothing is perfect anymore      also dirt will take up clearance keep everything sanitary clean like spotless one eyelash will have you chasing your tail most cb1100 require not adjustments even at 100k      up to .002 over is ok to tight is a problem even .001 too tight if my spec is like .005 and i see .009 ill leave it be

"i always run the bike and let it cool after adjustments made and recheck the clearance before sealing it up always let it cool over night before rechecking"

Can you please clarify how you do this? You have to "seal it up" before running it, don't you? Are you saying you put everything back together after making adjustments, run the engine, let it cool, then take it completely back apart again?

i take the cover off check clearance ,cams out adjust etc the  i just set the valve cover on the head warm the engine up then the next day i recheck if all is good i will reinstall the valve cover and new gasket seal it up always check when stone cold left over night

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does not have to be done that way i just dont want bikes coming back so ispend a little extra time to make sure they are good to go

 

[LucienLeFranc]

Noob question here, quite possibly a dumb one, so apologies in advance:

I seem to remember reading here or somewhere that some experienced folks skip checking CB1100 valves "since they're never out of spec for this precision machine," or something to that effect.

Did I misunderstand that? Or maybe I generalized one member's extreme minority opinion? Do folks truly not hassle with checking the CB1100 valves, or am I on the wrong track and they definitely need checking per the maintenance schedule?

Thanks in advance for helping the new guy.

 

[Cormanus]

LucienLeFranc, there is no such thing as a stupid question.

Try these threads for further information, The CB1100 Community Forum and The CB1100 Community Forum.

I'm no mechanic and I've never attempted to test the valve clearances on the bike by myself, but everything I read here about the experience of many members has led me to the conclusion that it's not such a big deal. There's certainly no need to check them per the service schedule as evidenced by Honda's decision with the 2017 bike to double that interval.

Over the years I've had some adjustments made to mine, but I haven't bothered to have them checked for about 50,000 kms and have noticed no ill effects.

The threads above contain a deal of empirical information about what people found when they checked the clearances.

 

[LucienLeFranc]

Thank you sir! I will read!

 

[1973cb750]

Noob question here, quite possibly a dumb one, so apologies in advance:

I seem to remember reading here or somewhere that some experienced folks skip checking CB1100 valves "since they're never out of spec for this precision machine," or something to that effect.

Did I misunderstand that?  Or maybe I generalized one member's extreme minority opinion? Do folks truly not hassle with checking the CB1100 valves, or am I on the wrong track and they definitely need checking per the maintenance schedule?

Thanks in advance for helping the new guy.

all this people i have done flashes for and talked too report most bikes dont need adjustment at all i checked mine at 8k and all were in spec     i have talked to a few owners with 150k plus and theirs didnt need it either a check is not bad to do every 10k or 20k

 

[dave]

It doesn't matter what you ride (unless it's electric), but all valves will eventually go out of adjustment. I believe that the majority of people who visit this forum ride their CB1100's quit conservatively, and what I mean by that is their bike rarely, if ever, sees redline. I've only had my CB1100 past 6,000 RPM twice since I've owned it. The higher the engine RPM, the more stress on the valves, and the more wear. Some people may choose to never check their valve clearances, and I understand why. It's a PITA if you do it yourself, and very expensive if performed by a shop (do you really trust the shop to work on your bike?). Can someone please respond who has had a recent valve adjustment performed by the shop and tell us how much it cost? As much as I hate checking the valve clearance on my "modern" motorcycles (I can adjust all the valves on my 1976 CB750F Honda in less than two hours), I still believe it is better safe than sorry, so I check mine. The damage caused by an out of adjustment valve (too tight) my appear to happen suddenly, but it doesn't. Excess wear accumulates over the course of several thousand miles until suddenly one day your bike fails to idle smoothly, or fails to start at all. By this time the damage is done, and you're talking a very expensive bill.

 

[MagnaRider]

I do agree with you Dave, but just to anyone else who comes into this thread I know 1973cb and my CB1100 see plenty of redline or full throttle runs.
I can't say for 1973 but my last valve check everything was in spec at 20k miles two years ago, but I will be checking it again this winter just for the sake of it. Hoping it is just a valve check again as to do the adjustment and pull the cams sounds like less fun lol