I'm in the process of checking my valve clearences.  I couldn't get my .04mm feeler gage into any of them, so they're all potentially tight.  I pulled each shim and replaced with my 2.15 mm test shim, then checked for the size of the gap.  Adding the test shim size to the feeler gage gives the exact gap, which I then need to subtract .03 - .08 mm from to get the new shim size?  If that's the case then my results are as follows:

              Original   Test   Measured             Minus      New
                Size     Shim      Gap     Total   Clearence   Shim
              ----------  ------     -----------  ------   ------------    ------
Valve 1       2.38   2.15       0.23    2.38        0.08     2.30
Valve 2       2.38   2.15       0.22    2.37        0.07     2.30
Valve 3       2.60   2.15       0.37    2.52        0.07     2.45
Valve 4       2.60   2.15       0.39    2.54        0.04     2.50

Does that seem right?  I'm losing .08 on each intake valve and .10 - .15 on the outtake valves...

Wait, measured gap is .23 to .39 with the 215 shim in?

If so, then you need a shim that is thinner than the 215.

Otherwise, I'm We Todd Did, and you're correct.  It's normal to go one or two shim sizes up or down, but three, hmm...is valve 3 an intake valve?  If so, just go to a 250 as well.

Valve 1 & 2 are towards the back of the bike, 3 & 4 are in the front.    I think the back are the intakes and the fronts are the exhaust, but I'm not sure...

Quote from: scratch on March 08, 2006, 11:34:45 AM
Wait, measured gap is .23 to .39 with the 215 shim in?

If so, then you need a shim that is thinner than the 215.

Huh?  With the 215 shim in, the gap is .23 to .39...that's a big gap.  A smaller shim would make that gap even bigger.

FlyingBeagle...some of those numbers are surprising.  It looks like valve 4 was open all of the time...Not good, especially if it is an exhaust valve.  Is the bike still apart?  I call for a remeasure.

-Turd.

You're right, my math is bad.  Can't even put the decimal in the right place (mentally).

I'll double check valve 4 tonight.  Would the bike sound weird of the valve was open at all times?  Would it even run?

I think if an exhaust valve is always open, you'd basically be putting a blowtorch to the exhaust pipe.  That would lead to failure of the exhaust system and big $$$ to replace it.

Quote from: flyingbeagle71 on March 08, 2006, 11:46:33 AM
Valve 1 & 2 are towards the back of the bike, 3 & 4 are in the front.    I think the back are the intakes and the fronts are the exhaust, but I'm not sure...

Look at the valve layout this way; two of the valves are near the exhaust side (front) of the engine, directly behind where the exhaust pipes are located, closer to the front wheel than to the back. Those MUST be the exhaust valves, because they open to let the burned fuel escape through the exhaust pipes.

The two other valves are located closer to the intake side (back) of the engine, where the carburetor intake boots and carbs are located. Those MUST be the intake valves, because they allow air and fuel to enter the cylinders from the carbs.

Traditionally, when you sit on the motorcycle facing forward, the cylinder next to your left leg is the Number 1 cylinder, and the others are counted moving across the engine. Since our GS only has two cylinders, that means the cylinder next to your right leg has to be the Number 2 cylinder.

Now, you can re-do your chart to show the clearances for Number 1 cylinder intake valve, Number 1 exhaust valve, Number 2 intake valve, and Number 2 exhaust valve. That will help us determine which cylinder you're referring to when you post the clearances.

Hope this helps you understand the valve layout better; now, I hope you'll recheck ALL the clearances again. It won't hurt you to double-check them; in fact, do it often enough, and you'll quickly become an expert on adjusting valves, and be able to advise others.

If you hit a snag, or just want someone to "look over your shoulder", post your location; there might be a member nearby who can help you through this. Good luck...

Quote from: flyingbeagle71 on March 08, 2006, 01:10:17 PM
I'll double check valve 4 tonight.  Would the bike sound weird of the valve was open at all times?  Would it even run?

The valves would not be open all the time since the valve clearance increases as engine temp increases.  If your measurements are accurate, the bike should idle lousy while cold but run smoothly after warm up.  If left uncorrected for a long time the exhaust valves could become burned.

That's a good indicator of needing a valve adjustment, the idle gets rough cold and smoothes out as it warms out if you have tight valves.  Too loose valves can be heard ticking.

Too satisfy my own curosity on this years ago, I checked the valves hot on a CB750 with shim over bucket valves set at about .003-.006" clearance cold and all the gaps were .015" or larger hot.  Valve clearance increases considerably on an overhead cam engine with an aluminum head.  Aluminum head expands more than steel valves as temp increases.

Set your valves to your calculations and recheck when done changing the shims.

i had the same problem when i did my valves after the 600 mile check. i don't think however had the bike before got them done. i just left it till i was able to take it to the dealer to get it fixed.

                             Original   Test     Measured               Minus        New
                                Size     Shim        Gap       Total   Clearence     Shim
                             ----------  ------    -----------  ------   ------------    ------
Cylinder 1 Intake         2.38     2.15       0.23       2.38        0.08         2.30
Cylinder 2 Intake         2.38     2.15       0.22       2.37        0.07         2.30
Cylinder 1 Exhaust       2.60     2.15       0.37       2.52        0.07         2.45 Probably going with a 2.50
Cylinder 2 Exhaust       2.60     2.15       0.39       2.54        0.04         2.50


I double checked the numbers and these seem solid.  I can add .01 mm to each and it will still go, but it's really rough.  I feels like the bucket is moving in that case.  The numbers in the table wipe the oil off the feeler gage, like in Kerry's video.

Should the valves have been this tight?  I'm dropping .08 - .10 in shim size on all valves...The bikes got ~4000 miles on it and I don't think they've ever been checked before.

I thought shim sizes only came in increments of .05"?

I did my 4000 mile valve check 400 miles ago and only my left intake was out of sinc. And I only downsized from a 265 to a 260.

I guess I am assuming that all GS engines came with the same size shims from the factory. Am I wrong in assuming this?

[quote author=flyingbeagle71 Should the valves have been this tight?  I'm dropping .08 - .10 in shim size on all valves...The bikes got ~4000 miles on it and I don't think they've ever been checked before.

Quote

No, they shouldn't have been that tight,  that is why I said above "If your measurements are accurate."

Do you have the crank set in the right position for checking?  It's best to check as indicated in the manuals.  However if you still have it opened up I'd suggest checking each one with the valve lobe turned up and directly away from the valve.  If a valve is not tight you can turn the bucket with your fingertip.  Make sure they are all tight as your measurements indicate.

Don't know about the wiping the oil off the feeler gage thing, but the feeler gage should have a light drag on it as you pull it thru and going to the next thinnest gage should move thru freely without drag.  It can be very difficult sometimes to get the thinnest feeler in the gap to start.

On a 97 GS I checked at 600 miles and then at every 8k miles after that.  No shim changes were required until 40k miles.  At 80k miles the intake valves still have original shims and proper clearance, but the exhaust valves have receeded into the seats and have been reshimmed several times until one is down to the min 2.15 shim.

Again assuming everything is as indicated and based on my experience, I'd be inclined to leave 1E with the 2.45 shim and .07 clearance and go to a 2.45 on 2E with .09 clearance. 

Someone questioned shim size increments above.  Replacement shims do come only in .05mm increments but the factory has sizes between these.  I've been thinking in inches for so many decades that I have to stop and figure constantly with all these mm thingys.  I set valves to .001-.003" clearance.   

Quote from: Budrick320 on March 09, 2006, 04:39:58 AM
I thought shim sizes only came in increments of .05"?

I did my 4000 mile valve check 400 miles ago and only my left intake was out of sinc. And I only downsized from a 265 to a 260.

I guess I am assuming that all GS engines came with the same size shims from the factory. Am I wrong in assuming this?

That is a good question, and the answer is that the shims vary from one valve to the next, and one engine to the next, as the engines roll down the assembly line. The engine builders check valve clearance and install whatever shims are needed; clearances are so tight that each head would have to be carefully assembled to spec ("blueprinted") if they even hoped to be able to use the same size shim for each valve. Since that isn't possible in the world of mass-production, the shims make up the controllable variable; IOW, the shim used with any valve is there to compensate for normal manufacturing tolerances. Since shims are available in a (relatively) wide range of sizes, it makes engine building MUCH easier than having to "blueprint" every engine that comes down the line.

If you've ever encountered the terms "blueprinted and balanced" when referring to engine building, "blueprinting" refers to an engine which has been carefully hand assembled (or more likely, RE-assembled) to make it as close to the engineering specs as possible. "Balancing" an engine requires weighing each piston, each connecting rod, and other components to find the ones that most closely match in weight. One connecting rod might weigh a few grams more than another, so the heavier one will have some excess material ground off to make the weights match as closely as possible. A few grams might not seem like much, but if you're building a racing engine with a 15K redline (just as an example), that minor difference in weight will become noticeable at redline in the form of vibration. The crankshaft will flex from moving the unbalanced conrod up and down, causing more wear in the bottom end... hopefully, you get the idea.

Bottom line is that modern mass-production doesn't allow the luxury of blueprinting and balancing the engine (except maybe at Ferrari), so variable shim sizes help to compensate for other variable tolerances during production. No two components are exactly alike, though they might only differ in minor ways, they are not identical. All Champion 809 spark plugs look the same, but there will be variations from one to the next that might not be visible to the naked eye. As long as they fit your GS and work as expected, should we really care about the variations? Of course not; the spark plug engineer designed the plug to be cheap and easy to manufacture, so engineering tolerances for certain sub-components (the electrode, the ceramic insulator, etc.) will be established that allow the majority of the plugs to pass QA inspections during the assembly process, which (among other variables), helps to keep the price down.

This is probably more than you wanted to know, but I'm hoping it will allow everyone to see the bigger picture about engine assembly from a different perspective.

Quote from: Budrick320 on March 09, 2006, 04:39:58 AM
I thought shim sizes only came in increments of .05"?

I did my 4000 mile valve check 400 miles ago and only my left intake was out of sinc. And I only downsized from a 265 to a 260.

I guess I am assuming that all GS engines came with the same size shims from the factory. Am I wrong in assuming this?

They come with all different sizes from the factory.  I have a couple in min that aren't to the standard .05 increment.  The replacements only come in .05 increments though, that is where judging what should go in to replace it can get tricky if you have an od size shim in there from the factory.