Shim calculation question

[JTGS850GL]

First let me say, pardon me for the newbie question if this has been asked over and over.

After reviewing many posts related to shim selection and calculations I found myself thinking of what would be the best way to baseline my 82 GS850. Since I have no maintenance history on her I though it best to go through a complete inventory of all shims currently used. I then began to become concerned with the possibility of many shims being too tight and no good way to identify just exactly how tight. What I'm wondering is, why not just replace each shim with the thinnest shim available and then measure the gap using larger feeler gauges to determine the exact size for each shim needed? Does this make sense or am I missing something? I can also use that shim as a place holder as I rearrange the shims for the correct size.

Also, I'm planning on doing a carb rebuild and the valve adjustments before the bike goes back on the road. Any opinions on which to do first or does it matter? I was thinking of doing the valves first since that may affect the vacuum test when syncing the carbs.

 

[1980GS1000E]

You are on the right track. Order a single 2.30 shim, install it at the different valves measuring the clearance as you go.

 

[Steve]

What I'm wondering is, why not just replace each shim with the thinnest shim available and then measure the gap using larger feeler gauges to determine the exact size for each shim needed? Does this make sense or am I missing something?

Yes, it makes perfect sense, but you are still missing something.

What you are missing is ... reading the instructions that came with your valve adjust spreadsheet. That very item is covered in instruction #8.

Also, I'm planning on doing a carb rebuild and the valve adjustments before the bike goes back on the road. Any opinions on which to do first or does it matter? I was thinking of doing the valves first since that may affect the vacuum test when syncing the carbs.

You are very correct in your final thinking, but they can be done concurrently.

Break the carbs down, get the first one in "the dip".
Remove the valve cover (you have to remove the breather cover first, on your bike), check your clearances, inventory your shims.
At this point, you will now know what you need to order: valve cover gasket, breather cover gasket, shims, float bowl gaskets. All of these items can come from Z1 Enterprises, and they will be there by the time the last carb is out of the dip.

You can order your o-rings for the carbs and intake boots at any time, but you KNOW you will need them, so go ahead and order them first from cycleorings.com. They will be there in just a couple of days, you can install the intake boot o-rings while waiting for your other parts to arrive and for the last carb to come out of the dip.

You should "bench sync" the carbs before installation, just to get them adjusted close enough to give them a fighting chance of letting the engine run. After the bike is started and warmed up, do the vacuum sync.

Any time you make a shim change, you should also do a vacuum sync, as the amount of air that each cylinder can ingest will be slightly changed by the shim change.

.

 

[tom203]

I'd probably get a 2.5 shim as my measuring stick to avoid addition errors. no shim on my 650 was less then 2.55 (42k miles). make sure you get a micrometer or somesuch to measure the shims you remove ,cuz they won't be exactly as marked.

 

[Agemax]

I'd probably get a 2.5 shim as my measuring stick to avoid addition errors. no shim on my 650 was less then 2.55 (42k miles). make sure you get a micrometer or somesuch to measure the shims you remove ,cuz they won't be exactly as marked.

and some may not be marked at all if they were fitted incorrectly!

 

[JTGS850GL]

You are very correct in your final thinking, but they can be done concurrently.

Break the carbs down, get the first one in "the dip".
Remove the valve cover (you have to remove the breather cover first, on your bike), check your clearances, inventory your shims.
At this point, you will now know what you need to order: valve cover gasket, breather cover gasket, shims, float bowl gaskets. All of these items can come from Z1 Enterprises, and they will be there by the time the last carb is out of the dip.

You can order your o-rings for the carbs and intake boots at any time, but you KNOW you will need them, so go ahead and order them first from cycleorings.com. They will be there in just a couple of days, you can install the intake boot o-rings while waiting for your other parts to arrive and for the last carb to come out of the dip.

You should "bench sync" the carbs before installation, just to get them adjusted close enough to give them a fighting chance of letting the engine run. After the bike is started and warmed up, do the vacuum sync.

Any time you make a shim change, you should also do a vacuum sync, as the amount of air that each cylinder can ingest will be slightly changed by the shim change.

.

Valve cover gasket, new half moons, intake O-rings, carb O-ring set are already ordered from cycleorings.com. Couldn't find the breather gasket at Z1 but I'll look again. If not, I'll pick one up form another source or local. Forgot the float bowl gaskets Guess I'll have to order those from Z1 as well.

Good suggestion on getting all the valve measurments done and working on the carbs while the shims arrive. I haven't talked to my local Suzuki dealer yet, but they may have a shim swap + $ program that could expedite the process of getting the shims I need though.

Thanks for the help guys.

 

[Steve]

Valve cover gasket, new half moons, intake O-rings, carb O-ring set are already ordered from cycleorings.com. Couldn't find the breather gasket at Z1 but I'll look again. If not, I'll pick one up form another source or local. Forgot the float bowl gaskets Guess I'll have to order those from Z1 as well.

Good suggestion on getting all the valve measurments done and working on the carbs while the shims arrive. I haven't talked to my local Suzuki dealer yet, but they may have a shim swap + $ program that could expedite the process of getting the shims I need though.

Thanks for the help guys.

On second thought, Z1 might not carry the breather gasket. If yours comes off cleanly, just re-use it. If it tears, cut a new one out of a cereal box.

If your float bowl gaskets come off without tearing, re-use them. It's not like they have to hold any pressure.

Talking to the local shop is a good place to start, but many of them will only sell you new shims. Some have been known to exchange, though. Some are free, others will charge a token amount. Just for reference, new shims from Z1 are just over $6, so keep that in mind when you discuss exchange prices.

You can also check into the GSR Shim Club for shim exchanges. I don't know any of the details how their system works, as I don't use them (I have my own stash for my bikes), but you can find them in the GS Parts and Services forum.

.

 

[Guest]

The shim club is an exchange also, send in a shim and get one back, cover the postage both ways. We also ask for a donation to join the group. The shim club uses the USPS for all swaps, so 2-3 days usually to get the shims. This would make the dealer swap the way to go if they don't gaff you too badly and if they have what you need. Ray