GL1100 carb mystery.

[kerryb]

1983 interstate to date: whole bike overhauled (woke up & put back in service) 3 years ago and parked in my garage near the ocean in Florida. Carbs were rebuilt then with new oem needles & seats. All new seals from Randakks. Stabil & non-alcohol gas for 9 months of storage. That worked fine till this year when the accel pump diaphragm failed, so replaced and checked to see nozzles squirt well. Now to the mystery, there is a little new hesitation just after butterflies open, then the power comes on fine. I found an idle mixture screw fell out of it’s place during carb removal (see pic) so I put that back in. What causes can you think of to explain the (new) stumble? I sprayed around the base of the manifold elbows for leak detection with no leaks found. I didn’t do anything to the carb rack except replace the accel pump diaphragm. How about some fresh armchair brainstorming to iron this out.

 

[mcgovern61]

If the accel pump diaphragm disintegrated, that is not good. There are chances that pieces of that diaphragm circulated the carbs. One other place I would look is the right here in each carb right below the butterfly. These holes can easily clog:

 

[kerryb]

That was another odd thing. The accel pump was spewing fuel out the top, but when it was removed, there was no apparent damage! After the new diaphragm went in I saw the accel nozzles squirt properly.

 

[Lowrider Bud]

Could it be a timing advance sticking? That can cause a stumble coming off idle. Hope you figure it out.

Later, Bud...

 

[mcgovern61]

Another thing will cause stumble off idle, the sync being off at higher RPM. I used to first bench sync, then idle sync with a hot engine and then sync at 3K rpm to verify all carbs are pulling the same. One time I had a good sync at idle, but could not get a good sync at 3K plus there was a stumble when I flipped the throttle. Turned out to be a sticking carb slide.

 

[kerryb]

I rode it about 20 miles today. The stumble is now running on only 3 cyls between 1500 rpm to 3 grand. Uneven banging (1 cyl missing) goes away at 3300rpm and above. If I whack the throttle open at any speed, you can tell the accerator pump & nozzles work right. So I’m off to pull the carbs again and find the plugged idle jet. Hope I’m right. It idles fine, so I could be way off base.

 

[kerryb]

Good news, there was a plugged idle jet in carb #4 hopefully that was it. I was nervous, the first three idle jets were clean. I’ll let you know tomorrow if I was right.

 

[mcgovern61]

Here's to hoping that was it!

 

[kerryb]

Nice to have my good runner back!

 

[kerryb]

Yup, good guess, it was a plugged idle jet. I love it when I guess right, not so much when I work sloppy and get dirt in a line.