Need a different carb perspective

[Fishead36x]

Hey folks I have an 82 gs650gl that I've brought back from sitting in my grandfather's barn for at least 15 years. Went over the electrical and sorted it out. Ultrasonic cleaned the carbs and rebuilt with kl kits. Also adjusted valves o-rings ext. Ext. Thanks to this site btw. The problem I have its drinking fuel as if it were through a straw. The floats shut the fuel flow off. Confirmed that today. I just need to know where to look next. It literally ate 3+ gallons of fuel in 30 miles and only fouled one plug. So I know it's one carb I don't know how it could possibly pull so much fuel while running. Thanks.

[Nessism]

https://gsarchive.bwringer.com/mtsac/~cliff/storage/gs/Mikuni_BS-CV_Carburetor_Rebuild_Tutorial.pdf

http://www.thegsresources.com/_forum/showthread.php?t=171846

https://www.thegsresources.com/_forum/forum/consumer-information/gs-parts-and-services/1703182-mikuni-bs-cv-and-vm-o-ring-kits#post1703182

[unfocused]

One cylinder, one vacuum line coming from the fuel petcock. Coincedence?

The GS's with the vacuum petcock are known for this. You have multiple options for repair.

I went with a tank adapter for 3/8" NPT and then purchased the appropriate petcock. Pingle has the adapter plates.

[Who Dat?]

Did it foul number 2 plug? That is the one with the vacuum nipple attached to the petcock. Check the diaphragm in the petcock for leaks.

[tom203]

Start by getting a new petcock…it’s most likely your problem…or will be soon. But you can test old unit by pulling off vac line at number 2 carb nipple and ensuring fuel doesn’t flow unless you suck on it in “on or res” spot.That’s a lot of fuel flow in 30 miles, so beware of fuel overflowing into crankcase….the angle of carbs means an overflowing carb drains into crankcase (when bike is parked level)

[Suzukian]

I think that fuel is going into your crankcase. there's no way you could burn that much fuel without fouling the plugs. It just doesn't make sense. As mentioned, just sucking on the tube the leads to the petcock vacuum line, and disconnecting the fuel line from it, should have the gas just immediately flow. or it's not working, the gas will flow in the on position (and Reserve). Check you crankcase level, and suck out some oil to see and smell if there is gas in there. Gas in the oil will lower the viscosity by a lot, you could ruin your engine.

[Fishead36x]

It's the number 4 cylinder. The other 3 are fine. Plugs look great. Thr plug is fouled in 30mi of riding. I just can't figure out where the fuel getting pulled from

[Fishead36x]

Thr petcock is new suzuki btw.

[Suzukian]

If it's Number 4 cylinder only, there's really only a couple of things that could cause that. A leaky float bowl, or one that is not adjusted correctly, or for some reason has gone out of adjustment, or a sticking float, or a broken needle valve seat. All involve taking the carb apart and checking in though. There isn't much left as far as gas supply left in the system. Still seems like a lot of gas to pass through one cylinder. I'd do the carbs over, as eventually, it's going to be your only option.