Adjusting the valves- went one size up and it still wasn't enough?

[AudiA4_20T]

Hey guys, so I'm starting to not get overwhelmed by this bike anymore. It seems that there is a proper approach and system to this and I'd like to have everything in line one at a time so I know that my GS is 100%! After this comes syncing the carbs and finally possibly adjusting the idle screws in the carbs.

Anyways, I started doing the valves on my bike and I measured all 8 valves. One was .08mm, one was .06mm, a bunch were .04mm, and 3 were under .04mm (smallest one I had) so I decided to change them.

After I got one size under shims for each one, they STILL would not clearance my .04mm feeler gauge. Thinking this was odd, I went back and measured the others, and they were just like I had measured them.

Now, when I take the shim out, there is most certainly clearance there, but what would cause the .05mm shim to still make the clearance under .04mm? It seems almost impossible. The only way I'm thinking that this could have happened is if possibly the previous owner put the wrong shims in?

TIA,
Clint

[cowboyup3371]

What size shims do you have in each cylinder? Are you also using Steve's worksheet?

[Big T]

Do you have a caliper and are you measuring the shims?

If there's not enough clearance, go down another size

Are you using Steve's spreadsheet?

[mike_of_bbg]

They can have negative clearance cold. Did you try turning the buckets to see if they could? If they can't you certainly have negative clearance. Have you tried turning the motor over a couple of times by hand to see if the shims seat down a bit?

It's often recommended to have a very thin "measuring shim" of for just such occasions.

[Nessism]

Many owners abuse their bikes and never adjust the valves. The clearance goes down as the valve hammers into the valve seat and eventually the valve never closes and burns.

Your bike has been abused in the past as evidence of the lack of clearance on those valves. If the next step smaller shim doesn't put the clearance in spec, you have no option but to go down one more size and try again.

Many experienced GS mechanics have a thin "checking shim" in the tool box for occasions such as you are experiencing: install the thin shim, measure the clearance, then calculate the proper shim to get the clearance in spec.

Good luck.

[esj001]

i had same thing happen to me--had to go down 2 sizes on like 3 valves to get good clearance on them---just go down another size and save those shims you dont use for next time

[Steve]

Are you also using Steve's worksheet?

Are you using Steve's spreadsheet?

Seems to be a general theme here. read my sig.

... If the next step smaller shim doesn't put the clearance in spec, you have no option but to go down one more size and try again.

Many experienced GS mechanics have a thin "checking shim" in the tool box for occasions such as you are experiencing: install the thin shim, measure the clearance, then calculate the proper shim to get the clearance in spec.

If you don't have a "checking shim" (yet), a quick check is to see if the bucket will turn easily. If it will turn, there is at least some clearance, so one shim size will probably do it. If it takes a lot of effort to turn, you will need to drop two or more sizes, there is no way to tell without changing and measuring.

Just for information, my spreadsheet will handle a "checking shim" up to SIX sizes smaller than what is necessary, but there is no way to guess how many sizes to change if it is too tight.

.

[AudiA4_20T]

Many owners abuse their bikes and never adjust the valves. The clearance goes down as the valve hammers into the valve seat and eventually the valve never closes and burns.

Your bike has been abused in the past as evidence of the lack of clearance on those valves. If the next step smaller shim doesn't put the clearance in spec, you have no option but to go down one more size and try again.

Many experienced GS mechanics have a thin "checking shim" in the tool box for occasions such as you are experiencing: install the thin shim, measure the clearance, then calculate the proper shim to get the clearance in spec.

Good luck.

Well that sounds like fun! Glad to know the bike's been beaten up. It was $500 so I can't complain that much. Plus, if everything worked great, I wouldn't be able to learn right?

i had same thing happen to me--had to go down 2 sizes on like 3 valves to get good clearance on them---just go down another size and save those shims you dont use for next time

Well it's nice to know someone else had this problem. I was pretty worried

If you don't have a "checking shim" (yet), a quick check is to see if the bucket will turn easily. If it will turn, there is at least some clearance, so one shim size will probably do it. If it takes a lot of effort to turn, you will need to drop two or more sizes, there is no way to tell without changing and measuring.

Just for information, my spreadsheet will handle a "checking shim" up to SIX sizes smaller than what is necessary, but there is no way to guess how many sizes to change if it is too tight.

.

Steve, what position are you referring to when talking about turning the bucket? Like should it turn when the lobe is on it? Or when the shim is out? etc. Thanks again

I'm already somewhat worried because one of the slots in the bucket was submerged under some oil so it was tough to get to, and I remember having a tough time trying to spin it around so I just gave up.

[Nessism]

Sorry to jump in and speak for Steve, but basically he is saying that if you can turn the bucket with your finger when the cam is in the proper adjustment position that means there is some clearance (above zero). In that case it's a reasonable guess that changing to one size smaller shim will put the valve in spec even if you can't get your feeler gauge in to measure the clearance.

[AudiA4_20T]

Sorry to jump in and speak for Steve, but basically he is saying that if you can turn the bucket with your finger when the cam is in the proper adjustment position that means there is some clearance (above zero). In that case it's a reasonable guess that changing to one size smaller shim will put the valve in spec even if you can't get your feeler gauge in to measure the clearance.

I see. So it's not a HUGE deal if the bucket won't move, just won't be as easy.. That's fine. I might try to see if I can get a caliper in there. If I can't just more guessing

[tkent02]

You're not understanding it, the shim spinning thing is just to tell you how much smaller you need to go... If the shim spins, you need to go one size smaller, if it is too tight to spin, go two sizes smaller. You still need a caliper to see how thick the one is that's in there now. Take the shim out, measure thickness with the caliper, get one the right size, install it and check the clearance again.

If it is way too tight, you may need to use the zip tie technique to get the shim out.

[MisterCinders]

Which method are you using for taking the measurements?

The Clymer method is inaccurate and might be part of your problem. I got whacky clearance results from it.

The better method is in the Service Manual. It involves fewer turns of the crankshaft, is faster and more accurate. win-win-win.

[AudiA4_20T]

You're not understanding it, the shim spinning thing is just to tell you how much smaller you need to go... If the shim spins, you need to go one size smaller, if it is too tight to spin, go two sizes smaller. You still need a caliper to see how thick the one is that's in there now. Take the shim out, measure thickness with the caliper, get one the right size, install it and check the clearance again.

If it is way too tight, you may need to use the zip tie technique to get the shim out.

I understood that, the buckets still aren't moving so I'm gonna try 2 smaller on each

Which method are you using for taking the measurements?

The Clymer method is inaccurate and might be part of your problem. I got whacky clearance results from it.

The better method is in the Service Manual. It involves fewer turns of the crankshaft, is faster and more accurate. win-win-win.

I looked at the service manual and the write-up on BassCliff's site

Another general question, What do you all do about the cam lobes spinning when the shim is out? Like when I need to pull all 3 shims out to exchange them, so I need to turn the crank over with the shim removed

[cowboyup3371]

Never turn the crank without shims in the buckets. Only replace one at a time.

[hampshirehog]

If you're going to spin the cams with the shims out you need to replace the shims with something. I've got some foreign coins that fit spot on for the job. Handy when playing musical chairs with the shims.