Bench sync- what is the stock mixture?

[samp615]

After cleaning my carbs I am trying to do a bench sync. Does anyone know the stock screw settings? I have a 1982 gs1100. everything stock.

[Steve]

The stock setting is what you are trying to avoid.

They were set up too lean to run properly.

By the way, you are using the term "bench sync", but describing the mixture setting.

What you need to do for your bench sync is to visually adjust the sync screws (the ones between the carbs) so the throttle plates are opening the same amount at the same time. You will see recommendations of using small drill bits, piano wire, and other various bits of things, I prefer to use LIGHT. Just hold the carbs up to a light and look at the sliver under the throttle plate. Adjust the sync screws so they are all the same.

Here is what you are lookng for:



Now, for your mixture adjustment, start with the screws three full turns out from lightly seated. After the bike is warmed up, slowly turn each screw in to see if there is any increase in engine speed. It might not speed up any (and it won't be much), so listen for a decrease in speed, then back the screw out 1/8 turn and move to the next one. When you have done them all, go back, check them again to verify. Stop the engine, turn each screw in, counting the turns, record that number for future reference. Note that they might not all be the same number of turns.

About this time would also be a good time to do your vacuum sync. The engine needs to be warm to do it. I like to set the mixture, adjust the vacuum sync, then re-check the mixture, now that I know each carb is pulling properly.

By the way, you should really do a valve adjustment BEFORE a vacuum sync. If you have to change any valve adjustments, you will have to re-sync the carbs.

You say you have an '82 1100. Chain or shaft?

.

[GateKeeper]

Steve thanks for your post, this has helped me to better understand, but I have one question, I get what you mean by having the same amount of light, or what ever one is going to use for clearance to ensure the throttle plates are open the same, my question is how much should they be open, or left open, or fully closed, once I go to put them back on the bike ? Or is what that big screw in the middle is for, to open them up the amount needed to keep the bike running, with choke off ?

[samp615]

great response.

Shaft

[thewiz]

BassCliff has a great website that explains all of this in great detail.....

http://members.dslextreme.com/users/bikecliff/images/GSR_Greeting.html

[BigD_83]

Once you have done the bench synch, turn the idle adjust all the way until the butterflys are closed, and then back in about 1 1/2 turns. That should get you close to 1100rpm. Just be prepared to kill the engine when you start it back up if it starts to race on you.

That info is somewhere in BassCliff's site, and it worked for me

[duaneage]

Use a 1/16th drill bit to gauge the throttle plates opening so they are the same. You will have to turn in the idle speed adjustment knob to open them up this far. After you have them the same, back the idle speed knob out until the plates rest in the bores. Then turn it back in 1 1/2 turns to initially set the idle speed. Any more and you will have a runaway engine when it starts.

This by no means excludes a proper vacuum sync. But it will get you in the ballpark. Don't crank down the 8 mm nuts that lock the adjusters, you will need to fiddle with them once it's on the bike.