What is the biggest change?

[egent]

I have been working on checking my vavle clearance. I have had to go back three times so far to get progressivly smaller shims. On exhaust #3 I have gone from a 2.80mm shim down to a 2.60mm shim, and still need to go smaller. The #3 intake made the same change, but is now good at 2.60mm. My question is are changes of this range normal and what is the larges shim differance anyone had delt with in the past?

thanks,
Dirk

[focus frenzy]

you have gone down .2mm and still need to go more? :shock: eeek!

thats a bunch, I have only needed to do small changes and only on a couple at a time.

you need to get a referance shim, 2.20 pop out old shim pup in the referance shim and using feeler gauge use gap to calculate the size shims needed.

[Nessism]

2.80 shims are typically what you find in a new engine. I'd bet you lunch that either the engine has never had a valve adjustment, or that particular shim is an original. Hopefully the valve(s) in question are not burned. Also, make sure you are using the factory cam positions to check the valves. If not, the adjacent valve can be pushing on the valve spring and skew the adjustment clearance within the camshaft journal clearance.

Good luck.

[egent]

I had the feeling that the 2.80 was the starting point on this engine. as 5 of the valves had that shim to start. Most only had to be adjusted by one shim to 2.75 however the cylender three needed more. intake went too 2.60 and exhust I hope to know tonight. Is there anyway to tell if the vavles are burnt without removing the head? I am trying to follow the factory PDF manual I have for the procedure, so I don't think that is an issue.

[Nessism]

Sorry my comment about burned valves caused alarm. The way to tell is with a compression test. Warm up the engine first and hold the throttle wide open while checking.

BTW, how many miles on the engine? 2.60 shims are not thin so most likely you will be okay. These GS engines are pretty stout.

[egent]

the bike is a 78 750E with about 43,000 miles. Ok, when I get the right shim in that last cyclender and can run the bike again, I'll check the compression.

[BassCliff]

Mr. egent,

After replacing a shim, spin the motor a few times. This will seat it properly in the bucket. Then take the measurement with the cam lobe at the proper angle. I've had to go down 2 sizes, but not 4. I guess it's been a while since your last valve clearance check. Keep us informed.

My experience is documented here.

Thank you for your indulgence,

BassCliff

[tomm]

I have a 78 GS750E with about 40K miles, and just completed a routine valve adjustment. I have one valve at 255, three at 270, one at 275, two at 265, and one at 260. The stock shims were mostly 280 and 285.

[TheCafeKid]

smallest i had to go on my 77 was 2.60...most were in the 2.7 or 2.75 range i think i have 2.65 in there too...

[egent]

I don't know when, or if, a valve adjustment was done on the bike last. I bought the bike back in June and have put about 5000 miles and decided that it was time to check the valves. Well 4 didn't need to be changed at all (1 at 2.80, 3 at 2.75), 2 need to go one size smaller (From 2.80 to 2.75). The last 2 valve(Both number 3 cylinder) needed major changing. One, as already mentioned, went from 2.80 to 2.60; the other started at 2.80 as well, but went down to 2.45 to finally get into the correct spec.

As to your suggestion of turning the crank to seat the shim, I was making sure to make at least two revolutions of the cams before checking the clearance. Do you think I needed to make more turns to seat the shim?