'82 GS650, running very oddly, someone help me make sense of this please...

[Cmarino]

Hi all,

I just put the bike back together after doing some work, part of which involved taking off the exhaust. The bike ran pretty well before, but now it has a lot of problems. So, first off, when I first reattached the exhaust and started it back up, I noticed I had a lot of leaking smoke out of the headers. I took it back off and reattached it tighter and added some JBWeld gasketmaker, and now there is no visible leak, but I'm assuming it's still not a perfect seal, but should be good enough. Now with the bike, I can not make any sense of how it currently runs. Depending on how I have the idle and choke set, it will either idle way too high, which makes sense for the idle being high, idle perfectly but will die if I give it gas, or idle around 1500 and run great for about 10 minutes, until it ultimately dies, and I have to mess with everything again. (which is extra frustrating because I thought I had it all fixed and took it on the road, and it died in the middle of the road and I had to sit in a parking lot for 20 minutes trying to find a good mix). My guess is that the fuel/air mix is off because of the header leak, but I can't find any resources that show where the screw actually is! Everything I see says it's on the side, but there is no screw visible on the side of these carbs. There's a screw on the top, on the engine side that I thought could be it, but messing with those screws has no affect. I don't think it's a dirty carb problem, because once again, it was running pretty decently before I had to take stuff apart. Any help / resources would be appreciated. Thanks

[Cmarino]

I guess this is probably a dumb question, but how do I adjust fuel and air mix on the carb?

[Rob S.]

I would do only one thing at a time. If before exhaust it was running good, after not, and you do anything other than tinker with the exhaust, you may be complicating things by a factor of...a lot.

Ask me how I know.

[Big T]

I guess this is probably a dumb question, but how do I adjust fuel and air mix on the carb?

you adjust the air/fuel mix by changing the components for each carb circuit - idle jet, main jet, needle, etc

The idle mixture screws are on the top front of each carb

[Nessism]

You might want to check out the Newbie Mistakes link in my signature to see if anything applies. The idle inconsistency sounds similar to an air leak. If you haven't chanced the intake boots & o-rings now would be a good time.

[cowboyup3371]

Did you remove the old and install new exhaust gaskets between the pipes and the head - item number 2 on the fiche:

2
GASKET
14181-05010 14181-18C00
$5.64

https://www.partsoutlaw.com/oemparts/a/suz/50d3fdbbf8700230d8b4daf7/muffler

[salty_monk]

Sounds like you need new exhaust gaskets, maybe new intake O rings, seal up the airbox with new foam, perhaps dip & clean the carbs.... it's normal on these bikes unless it's been done in the last few years.

Good luck. You're in the right place to find info & ask questions.

[tom203]

Get new exhaust gaskets..

“There's a screw on the top, on the engine side that I thought could be it, but messing with those screws has no affect”

sounds like you’ve been messing with the mixture screw on each carb....if so, you probably got it far off its happy spot. It needs to be about 2 to 3 turns out from a careful bottoming. This controls a fuel/ air mixture....once bike is sorta warmed up and “choke” is fully off this maintains a stable idle and supplies enough mixture to let bike transition to higher loading where the main jet/ needle takes over.
the mixture screw looks like this
70171CBC-DA42-4B28-823C-1907E4B8FA45.jpg

[Cmarino]

Ah, good catch. Didn’t even think about changing those big rings, figured they weren’t a problem. I’ll look into that

[Gorminrider]

There's a screw on the top, on the engine side that I thought could be it, but messing with those screws has no affect. I don't think it's a dirty carb problem,

the effect of turning a single idlemix is much less noticeable on a four-cylinder versus a two cylinder. If you have fiddled with them, without taking note of original positions it's Best to set them to spec. in the manual

but I can't find any resources that show where the screw actually is!

available here:
BikeCliff's Website