Carb Sync Question - 82 Suzuki GS1100G

[williamcryan]

I'm currently beginning to sync my carbs, but I wanted to verify my valve clearances before I did the sync. I found two intake valves tight and one exhaust valve loose. I replaced shims to bring the valves within range of 0.03 to 0.08mm, no problem.

#1 - Adjusting idle air mixture. I picked up Colortune to check firing at idle. I first used it on a friends 82 Suzuki GS1100L and he got yellow color and adjusted to blue as recommended. He took the bike for a ride and said the bike was running much better than before. I tried it on my bike and I can't get yellow, only blue.
Don't know why his idle air adustments have an effect and mine don't.
Any feedback?

#2 - Syncing carbs with Carbtune. I've used it before and it works great. I pulled the carbs, my main idle adjuster was very stiff and binding. It was making it very difficult to adjust idle. I realigned the idle adjuster and put the carbs back on.

Beginning the sync of carbs 3 & 4 with #3 idle adjuster, the bar on Carbtune goes to the top. The manual says, maybe a leak between carb and airbox or the carb and head.

Question: I'm thinking the link is from the clamps not seating properly. Intake boots have been replaced two years ago. The carbs were rebuilt last year. The bike has been running great. I just wanted to tune it up to run the best.

What else should I look for with #3 carb since I have the carb out and before in put the carbs back on?

Feedback would be appreciated. Bill

[Nessism]

Did you plug the vacuum line that normally runs to the petcock when syncing?

Regarding the "carb rebuild" performed before, did you install all new O-rings inside?

[Steve]

Did you do a "bench sync" before putting the carbs back on the bike?

Also be aware that the recommended sequence is to balance #2 to #3, then set #1 so it's just a bit higher than 2&3, then finally set #4 to the same level as #1.
Not sure why the order is important, but that is what is detailed in the Suzuki manual.



.

[williamcryan]

Response to 82 Suzuki gS1100 carb sync

Hi Ed, I have carbs out.
1. Plug vacuum line - No I didn't. I connected fuel and vacuum line to fuel petcock as for normal riding when doing sync.
By plugging vacuum line, if I understand, I would plug the vacuum line at the carb inlet and then switch fuel valve to run on prime, bypassing vacuum opening up petcock diagphram. Is that correct and what's the difference in the way I have set it up?

2. Carb rebuild replaced o-rings.

Bike had carb rebuild with new o-rings, nine months ago and carb sync was done and the bike has been running great. The only reason I'm resyncing is because I wanted to make sure the carbs were in sync after valves were adjusted to spec. Three valves were adjusted - #2 & 4 Inlet, #1 Exhaust.

Steve

1. I'm not sure what or how to do with a bench sync. With carbs out, prior to reinstall, I have set all four idle adjustment screws to 1/2 turn out, main idle adjustment screw to touch idle adjuster. I have set idle air/fuel mixture scews to 1 1/2 turns out, but adjustment seems to have no effect, maybe a touch of increased or decrease speed. I go with the setting that just increases the speed. I didn't change float settings, the bike ran great before rebuild and has been running great since rebuild.

Could you please explain 'bench sync' please.

2. Sequence of syncing - Thanks for clarifying the sequence and the manual reference.

Thanks guys, Bill

[BassCliff]

Hi,

You might find some of this information helpful.

Carb Notes: Synchronizing/Troubleshooting

Carb Specs: Float Height/Jetting/Cleaning


Thank you for your indulgence,

BassCliff

[williamcryan]

Reponse - 82 GS1100G Carb Sync

Bike is running smooth and strong. Thanks very much guys.

I missed reading basscliff's tips and links before I reinstalled the carbs, but I did the basic settings that was close but not as good. I'll catch up the next time.

I put the carbs back in and followed the sync sequencing order. I ran fuel off prime and plugged the vacuum hose from #2. That must have been where I got off track in the carb sync. My #3 reading in the Carbtune column showed the rod going to the top of the case and the others carb column readings were way lower. Now #3 shows near mid range and the other carb columns match up closely right away. #2 and #3 match and #1 and #4 match.

BUT, I wasn't able to get the distances between the inner and out carbs to match as shown in the manual. They are about 1" apart. It looks like I need to resync and go one more time on adjusting to bring the distance closer to match that of the manualing.

The bike is running very good and I'll evaluate whether to resync again now or later.

Thanks all for the help. Bill

[BassCliff]

Hi,

On my last carb sync, this is where I started.



And this is where I ended up. Close enough.



According to the factory manual for my bike (because I have the crossover "pre-muffler":



It's very difficult to get the levels exact. Pretty close is close enough. My bike runs smooth, almost no vibration at the handlebars at freeway speeds.


Thank you for your indulgence,

BassCliff