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Those valve clearances

  • Thread starter Thread starter rickt
  • Start date Start date
R

rickt

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After the three hour struggle to remove the cam cover from the '78 GS750C, I finally got back to garage last night to check the valve clearances. The history: bike was parked in 1981 with 2009 miles. Has not been started since.

Somehow I assumed that an extremely low mileage cycle would not even need the valves touched. Wrong-O! Three of four intake valves have clearance less than 0.004 mm (smallest feeler gauge I own). One exhaust valve is 0.10 mm. All others are within the 0.03-0.08 mm specification.

So, is my next step to remove the shims one at a time to determine thickness? I believe I need a tool to depress the tappets. Who is the best vendor for this? Will I have any problems removing the shims from the valves with the <0.04 mm clearance?

Thanks,
rickt
 
If it has not run in 27 years I would get it running first and then adjust the valves to let things settle. Dan
 
Z1 enterprises has the correct tool, some folks like the zip tie method. I think the tool is easier, quicker, and safer but I've used the zip ties too, just depends on what you have.
No worry about getting the shims out.
Pull them out, read the shim sizes and measure them too, figure out which ones you can swap and which you need to buy.
Don't rotate the engine with any shims missing.
 
rickt said:
After the three hour struggle to remove the cam cover from the '78 GS750C, I finally got back to garage last night to check the valve clearances. The history: bike was parked in 1981 with 2009 miles. Has not been started since.

Somehow I assumed that an extremely low mileage cycle would not even need the valves touched. Wrong-O! Three of four intake valves have clearance less than 0.004 mm (smallest feeler gauge I own). One exhaust valve is 0.10 mm. All others are within the 0.03-0.08 mm specification.

So, is my next step to remove the shims one at a time to determine thickness? I believe I need a tool to depress the tappets. Who is the best vendor for this? Will I have any problems removing the shims from the valves with the <0.04 mm clearance?

Thanks,
rickt
Click to expand...


Wait, you say they are closer than .0004 or is that a typo? Cos if so, where in the world did you get a feeler that goes that small, and where can i get one?? Hehe. I am assuming that you actually meant .04mm? So lets go from there. The problem you may run into is something that i dealt with recently on a motor that i picked up off ebay with low miles, but had sat a while. My exhausts were all in good clearance..thankfully, but some of my intakes i had to drop as many as THREE shim sizes, which if you didnt know, is quite a bit. Basicly those valves simply were never closing. Thankfully, that side of the valve train doesnt get as hot as the exhaust, so no burnt valves, but that would be the serious risk there. Basicly, if your valves are tighter than your smallest feeler, you're going to have to kinda guess, or bracket, your shim size, especially if you try the next smallest and it doesnt work out. There are a few methods to depressing the bucket in order to get at the shims. One is naturally, purchasing the tappet tool, which, if you want it fast and cheap, go to www.Z1Enterprises.com If you order it tomorrow, you'll likely have it wednesday or thursday. The tool works, but is somewhat fiddley, especially on the inside cylinders. I ended up busting my knuckles up something fierce with it slipping off the bucket, slipping off the cam, etc etc. Eventually i got it to work, but there is another way that is much easier, tho there is SLIGHT risk involved. Do a search here on the board for the " Zip Tie Shim method" or something like that. Basicly what you would do here, is use a nice long NEW (very key that you use a nice new pliable one) zip tie. You would turn the motor over by hand, untill you can see the valve that you need to replace/remove the shim in open thru the spark plug hole. You then insert the zip tie (which you want to fold over, and tape so that if it breaks, it doesnt fall into the cylinder...ask me how i know) above the valve, and slowly turn the motor so that the valve begins to close, the zip tie will trap the valve, keeping it open, and the bucket down, so that you can get the shim out when you turn the motor so the cam lobe is out of the way. Read up on this method, If done right and attention is paid, its much quicker than fighting with the special tool, and CHEAP, and you can do it TODAY instead of waiting for your tool...

BTW, your shim thats .10mm, is fine. Its okay to be a little bit LOOSE ( i wouldnt suggest being more loose than .11 or .12 tho, for risk of floating a shim at high RPM) and with time, it will get beaten into spec anyway. And NEVER turn the cams without a shim in the bucket, as they will get scored up. No good.
 
I agree with Dan in that the clearances may move around some due to contamination on the valves if the engine has not run recently. I'd go ahead and adjust them now but check again shortly after you get it up and running just to make sure.
 
Missed just one decimal point in my number: 0.004 should have been 0.04 mm. Always put a zero to the left of the decimal point (i.e. 0.0...). Just a habit after 30+ years as a chemist! Sorry, I don't have a source for the 0.0004 mm feeler gauge - don't think you could actually hold on to it, let alone slide it between the cam lobe and shim!

rickt
 
And while you are at it, send me an e-mail (not a PM) with a request for my valve adjust spreadsheet. It will help you with the math, determining which shims you need for proper clearance. It will also keep track of your shims from one adjustment to the next.

.
 
Get yourself a feeler gauge that goes to .03 mm. They are worth it. Problem is, if your clearance is just less than .04 mm (say .037), you have to use the next smaller shim which is .05 mm smaller. Then you end up with clearance of .087 which is over tolerance.

It saves a lot of time and grief because lots of my clearances are > .03, but not > .04.
 
Last edited:
flyingace said:
Then you end up with clearance of .087 which is over tolerance.
Click to expand...
Yes, they are technically over tolerance, but well within the realm of useability.
Since they will likely be just under tolerance on the next adjustment interval, it will not hurt anything to change them now, and not wait until next time.

.
 
Steve said:
Yes, they are technically over tolerance, but well within the realm of useability.
Since they will likely be just under tolerance on the next adjustment interval, it will not hurt anything to change them now, and not wait until next time.

.
Click to expand...

True , I'm just saying there is no reason they can't be kept within the factory recommendations. The extra noise of looser valves is enough motivation for me to keep them within tolerance.
 
flyingace said:
True , I'm just saying there is no reason they can't be kept within the factory recommendations. The extra noise of looser valves is enough motivation for me to keep them within tolerance.
Click to expand...
What extra noise? People keep complaining on here about valve clatter on the 8v motors. Im sorry but i just dont hear it. Sounds like sweet music to me...
 
Thinking about shims!

Thinking about shims!

As I wait for my tappet depressor to arrive, I've been thinking about the procedure and how to manage the shim situation. From my initial measurements it appears I will have to change a number of shims. As I understand the procedure I must not rotate the cams without a shim for every valve. Therefore, I can remove only a single shim and it would seem to be impossible to use any of my current shims on other valves since this will require rotating the cams with at least one shim missing. Speaking of missing - am I missing something???

It would appear that I need to remove one shim at a time, measure it and determine what the replacement shim should be. Then I will need to order the proper replacement shims and replace them one at a time.

Does this sound right?

rickt
 
Measure every clearance, and record them on a spreadsheet or just a plain old drawing. When your shim tool arrives, remove each shim, read the thickness on it, measure it with calipers or a micrometer, reinstall, and record that info. Now look at your data. You might be able to switch a few shims around without having to buy replacements. Of course, you need at least one extra shim to do this.

I've done clearance adjustments where all eight valves were out of spec, but I only needed to buy a couple new shims to make everything kosher, because I could swap most of them around.

It sounds a lot harder than it is. You just have to take your time and analyze what you have.
 
rickt said:
As I wait for my tappet depressor to arrive, I've been thinking about the procedure and how to manage the shim situation. From my initial measurements it appears I will have to change a number of shims. As I understand the procedure I must not rotate the cams without a shim for every valve. Therefore, I can remove only a single shim and it would seem to be impossible to use any of my current shims on other valves since this will require rotating the cams with at least one shim missing. Speaking of missing - am I missing something???

It would appear that I need to remove one shim at a time, measure it and determine what the replacement shim should be. Then I will need to order the proper replacement shims and replace them one at a time.

Does this sound right? rickt
Click to expand...

As Griffin said, measure all your clearances, record them. You WILL likely be able to swap some. But you WILL need an extra shim (should have ordered one when you ordered your valve tool...DRAT :P ) Then you can do what he said, OR..(and i find this HONESTLY to be easier to inventory your shims, and if you know what you're doing too..) You CAN remove your cams to inventory them all at once, frankly, i find this both easier, and actually safer than rotating the motor by hand a couple 20 times. Now, if you've NEVER done this, i wouldnt recommend it, just follow others advice, because removing the cams requires you to RETIME them when you put them back in...its really NOT hard, but ive youve never done it before, it can be tricky.
 
TheCafeKid said:
What extra noise? People keep complaining on here about valve clatter on the 8v motors. Im sorry but i just dont hear it. Sounds like sweet music to me...
Click to expand...

Take your shims out and replace 'em with nickels. That should be a real symphony for ya.
 
Killer2600 said:
Found a new way to sink money into your bike have ya :lol:
Click to expand...
HAHA! That was pretty good :) I dunno, none of my 8vs make that much clatter. Well, my 1100 is a bit clattery at the moment, but thats cam CHAIN clatter, cos my tensioner needs cleaned and rebuilt. but ive never really heard valve clatter from my motors... maybe im deaf? All those years playing metal have finally taken their toll...lol
 
I am another one that just cant hear the difference between a valve adjusted to 0.08mm and another at 0.09mm. :-s

Might be able to hear the difference between 0.09mm and 0.04mm (one shim size), but once the helmet is on and the engine is singing at 5,000 rpm down the road, who cares? \\:D/

.
 
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