Cams/Shims - no gap - double checking procedure

[Gregory]

78 gs1000. I may be missing something about the process, or just dont understand.....

I took valve cover gasket off and have now found the right set of feeler gauges to use. .04 mm, .06mm, .08mm, .09mm They are super thin and flimsy.

I followed the instructions on turning the cams facing forward but cant even get the .04mm to go between the cam roller and shim.

My question is this: Since the shim goes up and down, and seems spring loaded, what keeps it from not having a gap at all, even when the cam is positioned the highest?

Am I missing something other than brains?

 

[hampshirehog]

The shim sits in (on top of) an upside down bucket. The bucket sits on top of the valve and that valve is closed by a spring - a strong spring that takes a fair bit of compressing. Once the valve is closed the spring is still exerting an upward pressure but it is restrained from moving by the closed valve. So when the valve is closed the bucket is under no pressure.

 

[Steve]

The only thing you are missing is some clearance, and possible the smallest shim. :-k

Smallest clearance allowed is .03mm, which isn't all that much thinner, but might tell you that you at least have minimum clearance.

Also need to make sure you are checking the shims correctly, as it is rather confusing in any of the manuals. I like to start with exhaust #1. (Note that #1 is under your clutch hand, #4 is under your throttle hand.) With the cam lobe for exhaust #1 pointing FORWARD, you will see that #2 EX is pointing UP. In that position, measure BOTH #1 and #2 exhaust. Use the 19mm nut on the right end of the crank to turn the crank 1/2 turn (180 degrees). You will see that intake lobe #1 is pointing UP, #2 intake is pointing REARWARD. In that position, measure BOTH, #1 and #2 intakes. Rotate the crank another 1/2 turn, you will see that exhaust #4 is pointing FORWARD, and #3 is pointing UP. Without moving the crank, measure BOTH, #3 and #4 exhaust. Rotate the crank a final 1/2 turn, check intakes #3 and #4.

The manual shows a picture of two lobes in the proper position, but is not very clear that you measure BOTH valves without moving the crank.

If that is how you measured the clearances, it's time to inventory your shims, as it seems that every one of them needs to be at least one size thinner, but you won't know what you need until you know what you have.

Reading your description, it appears that you might have had the cam lobe pointing away from the valve when measuring the clearance. That is not the proper orientation for consistent results.

There are two methods to remove the shims for inspection. One involves using the official tool, but some of us have not mastered the knack of using it. Many of us use what we call the "zip-tie method" to hold the valve open far enough to remove the shim. Whichever method you use, REMOVE ONLY ONE SHIM AT A TIME AND PUT IT BACK IN PLACE BEFORE MOVING THE CRANK. Record the size of the shim as you inspect it. I offer a handy spreadsheet that does this quite well, see details in my sig.

Once you see what shims you have, you can see if you can shuffle some of them around (AFTER getting your new replacement shims, so you don't move the crank with an empty shim bucket) so you don't have to buy as many shims.

.

 

[Guest]

.04mm is still within range, so the fact that you can't get a .04mm in there might mean you need to go lower. (.03-.08mm is the range.)
Here's the service manual. Checking and adjusting valves start on page
3-5.
http://www.mtsac.edu/~cliff/storage/gs/GS1000_C-E-S-L_Manual.pdf

This might help you,
http://members.dslextreme.com/users/bikecliff/images/gs850valve_adjust.pdf

Perhaps this also.
http://members.dslextreme.com/users/bikecliff/images/valve_tool_zip_tie.pdf

 

[Big T]

78 gs1000. I may be missing something about the process, or just dont understand.....

I took valve cover gasket off and have now found the right set of feeler gauges to use. .04 mm, .06mm, .08mm, .09mm They are super thin and flimsy.

I followed the instructions on turning the cams facing forward but cant even get the .04mm to go between the cam roller and shim.

My question is this: Since the shim goes up and down, and seems spring loaded, what keeps it from not having a gap at all, even when the cam is positioned the highest?

Am I missing something other than brains?

See the advice above and the links - just a rookie mistake, I'll bet

One thing not mentioned is that when you have the cam lobe properly positioned, you should be able to rotate the bucket with your finger. You'll want to do this so that little cut out in the bucket is towards the outside, so you can get a pick or tweezers in there and pull out the shim. Rotation generally means there's some clearance

Also, get a cheap caliper at Harbor Freight and measure the shims as they come out. The stamping isn't always accurate and this can drive you crazy trying to get the necessary clearance. Get a Sharpy and write the true measurement on the shim if it's different from the stamping

Do the inventory and email Steve for his spread sheet. It's a great tool that will come in handy in the future.

Also, order a valve cover gasket right now if yours tore. You won't believe how much oil sloshes around in there

 

[bwringer]

This always seems to spark an incredibly stupid argument for some reason, but... it's worth mentioning just in case:

Are you TRIPLE-DOG 110% SURE that you're using metric feeler gauges that read in .01mm increments and NOT inch feeler gauges that read in .001 inch increments?

Sometimes both measurements are written on each blade, and it's VERY VERY easy to get confused as to which measurement system you're using.

Also, it's VERY VERY EASY (like, I do this at least once every valve check) for these thin feeler blades to get stuck together.

'Nuff said.



With all that out of the way, it is indeed fairly common to find that several valves in a neglected engine are at zero or close to zero clearance. GS valve clearances tighten over the miles, and valve checks were widely considered "scary" for some strange reason, so lots of owners simply ignored this required maintenance.

Around 10,000 to 15,000 miles, the bike became harder and harder to start, started backfiring, became less and less pleasant to ride, and one sunny morning refused to start at all. It was then shoved to the back of the garage for a couple of decades, and all too often the title was lost and the carburetors removed, disassembled, and scattered to the four winds.

 

[bwringer]

Also, get a cheap caliper at Harbor Freight and measure the shims as they come out. The stamping isn't always accurate and this can drive you crazy trying to get the necessary clearance. Get a Sharpy and write the true measurement on the shim if it's different from the stamping

Agreed on all points.

HF also now carries a VERY nice digital micrometer that is more precise than the calipers and reads in millimeters (.001mm) or inches (.0001").

$34.99 list price, and under $30 with one of the ubiquitous 20% off coupons you'll find in any gearhead-oriented magazine.

http://www.harborfreight.com/digital-micrometer-68305.html

 

[Steve]

This always seems to spark an incredibly stupid argument for some reason, but... it's worth mentioning just in case:

Are you TRIPLE-DOG 110% SURE that you're using metric feeler gauges that read in .01mm increments and NOT inch feeler gauges that read in .001 inch increments?

Sometimes both measurements are written on each blade, and it's VERY VERY easy to get confused as to which measurement system you're using.

Also, it's VERY VERY EASY (like, I do this at least once every valve check) for these thin feeler blades to get stuck together.

All very true. :clap: :clap:

Although it is recommended to use metric feelers, it's not all that necessary, just be sure which one you are using.

If your feelers have both inch and metric measurements, there is a very good chance that they are inch feelers with metric approximations printed on there, too. I don't think I have ever seen metric feelers with inch approximations.

One other souce of confusion (not yet apparent in this case) is the fact that the metric specs are .03-.08mm and the inch specs are (roughly) .001-.003". The confusion comes from the fact that there is a "3" in both sets of specs, but one is the maximum, the other is the minimum, and some people lose track of how many zeroes there are between the decimal point and the three.

It is VERY easy to have two feelers stick together, so if you are using your .04mm feeler, make sure you can see your .05 to make sure you are not actually trying to measure .09mm.

.

 

[Gregory]

Thanks All. I am going to spend some time this morning re-reading these posts.

Yes I have the mm readings on the guages and yes they have both on them. I was also using the manuals and links that were suggested.

I guess I was wondering how this bike could have started and ran with dirty carbs AND zero valve gap. I also woke up wondering if the paper towels I shoved in the spark plug holes could create enough back pressure to push the shims up to where it appears there is no gap.

The statement above....

"With all that out of the way, it is indeed fairly common to find that several valves in a neglected engine are at zero or close to zero clearance. GS valve clearances tighten over the miles, and valve checks were widely considered "scary" for some strange reason, so lots of owners simply ignored this required maintenance."

....makes me feel more assured of the fact that i really will need new shims. BUT if there is zero gap, could there actually be less than a zero gap? Meaning, if I order shims that are .08mm thinner than the ones on the bike....would I definetily be at about .08mm gap?

I already ordered the new gasket... but also read that the half moons have to me replaced. They apear to look fine. Are they like gaskets?

By the way, let me say again how much I really appreciate you guys and this site. I sure hope I am able to pay you all back somehow, by at least passing the knowledge on to other GS'ers down the road.

 

[Steve]

Several issues here, let's address them:

Yes I have the mm readings on the guages and yes they have both on them.

In that case you have INCH feelers, please use the INCH markings, not the metric ones.

I guess I was wondering how this bike could have started and ran with dirty carbs AND zero valve gap.

You don't know that it has ZERO gap, only that it has less than you can measure. There might be .03mm, which is allowed, but you can't measure it, so you don't know.

I also woke up wondering if the paper towels I shoved in the spark plug holes could create enough back pressure to push the shims up to where it appears there is no gap.

Why do you have paper towels stuffed in the spark plug holes while you are turning the crank? :-k

Even so, having paper towels in there is NOT going to create ANY pressure in the cylinder, and certainly not enough to move the valves. The valves are stopped in their travel by the edge of the valve sitting on the valve seat, and nothing short of physical impact from the piston is going to make it move any farther. Certainly not any "pressure" from a paper towel.

....makes me feel more assured of the fact that i really will need new shims. BUT if there is zero gap, could there actually be less than a zero gap?

Again, you don't know that it's "zero gap", only that it's less than you can measure. And yes, it's possible that something has happened to make it "less than zero".

Meaning, if I order shims that are .08mm thinner than the ones on the bike....would I definetily be at about .08mm gap?

You can't order shims that are .08mm thinner than what you have, they come in increments of .05mm, which happens to be the entire range of clearance spec.

Recommended procedure:
Inventory your shims. Remove one shim, inspect (or measure) the size, record it. Put it back in place. Continue until you have all sizes recorded. Determine which is your thinnest shim. Remove it, replace it with a quarter. Yes, that's a 25-cent coin. Move that thinnest shim to another location, measure the clearance, record it. You might have too much clearance now, but at least you can measure it and compare it to the size of the shim that you have in there now, and KNOW what shim size you will need.

Those of us that work on "new" bikes relatively often will have a thinner "checking shim" that we use instead of a quarter. (Don't forget to get your quarter back out.)

Also note that all of this effort is only necessary ONE TIME on this engine. After you get done, you will KNOW what shims are in there (especially if you get my spreadsheet

) so it will be a simple matter of looking to see which clearances are approaching the minimum level, noting the shim size that's in there, and ordering the next smaller shim ahead of time so you have it handy when you do your valve check.

.

 

[Gregory]

Thanks Steve. I like the suggestion of the using the quarter...

The three feeler gauges that I "thought" were in the spec range read:

.0015 and below it 0.04mm
.0025 and below it 0.06mm
.003 and below it 0.08mm

 

[Steve]

The three feeler gauges that I "thought" were in the spec range read:

.0015 and below it 0.04mm
.0025 and below it 0.06mm
.003 and below it 0.08mm

As I said before, the "below it" readings are APPROXIMATIONS.

.0015" = .0381mm
.002" = .0508mm
.003" = .0762mm

And yes, those are the only feelers you are likely to use, once you get them set correctly.

.

 

[Gregory]

Ok stage one is done. You guys made it sound a little quicker and easier than it actually turned out for this newbie.

Since the PO or factory put the shims in with the numbers up, I had to guage all of them. I learned how to convert from inches & hundreths of inches to millimeters by multiply by 25.4

All of my Exhaust Valves were basically 2.85 mm

#1 Intake and #2 Intake were both 2.80, #3 Intake 2.75, #4 Intake 2.70

It was kind of simple using the zip tie method on the Intake side but I had trouble doing it on the exhaust side. I actually cheated and ran a piece of plastic through the exhaust manifold ports instead of though the spark plug holes.

It took a lot longer than I imagined, so I am not looking forward to doing it all over again to measure with the thinnest shim.

 

[Steve]

The nice thing is, though, that you only have to inventory all your shims ONE TIME, if you bother to record them. Next time you need to check your clearances, you will already know what's in there. And, if you note which ones you leave with clearances on the low side, you will know which ones might need new shims, and will be able to have them already on-hand when you open it up.

Once you know what's in there and have shims ready, the whole process takes less than an hour.

Need a convenient way to record your shims? Read my sig.

.

 

[Gregory]

Hi Steve, Thanks for the calculator, ​

I hope it is not a bother for you to look at these. (For background, the originals were - Exhausts all 2.85 and intakes were 2.8, 2.8, 2.75, and 2.70) and couldnt get a reading on any of them. -- which is why the results are confusing to me.​

I used the 2.70 from the #4 intake to calculate everything EXCEPT #4 (the BIG gap on the quarter was .30" or 75mm)​

Assuming that I didnt make any mistakes with glued together guages or improper positioning, the spreadsheet results are below.​

BTW: On the #1 intake - .05mm was loose, but the .06mm wouldnt quite fit.​

oops, spreadsheet did not convert I will email it to you directly

2.80 2.80 2.75 2.80exhausts

2.70 2.80 2.75 ?? intakes

 

[matt1100]

Those may be the originals. No surprise there is no gap

 

[Gregory]

Since this last posting Steve has generosly given of his spreadsheet and time in helping me figure out which shims to order.

I had a couple that I found were ok after Re-Measuring the gap. (I may have had some feelers stuck together, cleaned the oil off with carb cleaner and WALA good results)