Best way to find air leak?

[danny01975]

I am the new owner of a 1982 GS1100GK. This bike is in excellent condition and was "restored" by the PO. The bike runs pretty good but stumbles a bit in different throttle positions when it's cold. Only after about an hour or so of riding does it clear up. Even then, sometimes it doesn't. It stumbles at launch (only when cold) , and at WOT (most of the time). It's fine in the middle and when cruising. Following the advice of the Top Ten Newbie Mistakes on this forum, I'm going to do a full teardown and cleaning of the carbs and document exactly what jets are installed. I know they're larger than normal but I don't know what size. Will do all of the other maintenance items as well before I start troubleshooting.

My question is, if spraying starter fluid around the intake boots isn't a reliable method for finding air leaks, what is? When I re-install the carbs I want to make absolutely sure there are no air leaks.

[Rich82GS750TZ]

Good idea to just go ahead and do a thorough clean like you plan. Don't take shortcuts. Follow this tutorial by Nessism.

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

Good Idea to just go ahead and order a new set of o-rings from Nessism for the rebuild.
You'll want to order new o-rings for the carb boots, the ones that seal the boots to the head. You'll have to evaluate whether the boots themselves are still pliable enough to seal. Spraying almost anything around those boots while running should reveal any leaks in that area, even water, WD-40. Doesn't have to be starting fluid. In fact, I don't think I would use starting fluid. Just my opinion. You're looking for any change in engine RPMs when you spray something around those boots.
While you're at it, also a good idea to refurb the cam chain tensioner.

https://www.bwringer.com/gs/camchaintens.html

Oh, and you ride your GK at Wide Open Throttle "most of the time"?

[danny01975]

That's the tutorial I plan to follow. Will check out the cam chain tensioner link as well. Thanks for the tips!

Oh, and you ride your GK at Wide Open Throttle "most of the time"?[/QUOTE]

And is there any other way to ride! lol.

What I really meant there is that most of the time, when at WOT, it will hesitate. But sometimes it doesn't which is weird that it's inconsistent.

[Rich82GS750TZ]

I kinda thought that's what you meant. But, figured I'd bust you ba!!s about it anyway. Good luck with your project.

[rphillips]

Just thinking, just for kicks, while waiting for "O" rings, run a tank of fuel with a big dose of "Seafoam" through it. Wouldn't count on fixing problem, but what if it does?... And No, I don't own stock in Seafoam.

[danny01975]

Just thinking, just for kicks, while waiting for "O" rings, run a tank of fuel with a big dose of "Seafoam" through it. Wouldn't count on fixing problem, but what if it does?... And No, I don't own stock in Seafoam.

Couldn’t hurt. I’ve always used seafoam but never been sure if it’s actually doing anything. That would be a good test!

[LAB3]

Seafoam is your friend! Also, I was recently in a spot where I was getting low on gas and the only thing available was 93 octane ethanol free gasoline. At $4.75 a gallon I only bought enough to get me to a gas station but holy cow, the bike ran great after running some of that through it!

[Rob S.]

...93 octane ethanol free gasoline.

We don't have any of that here in the Big Apple.