Will not run below 3000 rpm after carburetor rebuild when warm


Information and questions on GL1100 Goldwings (1980-1983)
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Hansmann
Posts: 8
Joined: Thu Aug 30, 2018 2:08 pm
Location: Copenhagen, Danmark
Motorcycle: 1982 GL1100A standard

Will not run below 3000 rpm after carburetor rebuild when warm

Post by Hansmann »



Hi forum,
I have run into a very frustrating issue with my GL 110 carburetor that I hope the forum can guide me to a solution. I’ve had my carburetors off and sent for a professional overhaul. The bike was running ok before service. After the carburetors came back, I had some issues with no 2 that wasn’t delivering fuel at all. I took it off and sent it for service separately, and got it back fixed. The throttle has both wires replaced, it is perfectly mounted, and the return pull is strong and closes with a “snap”. The air filter is fit and tight to the plenum. When I start the bike, it only needs very little choke but starts swiftly! It runs very unevenly, but this expected because no attempt at balancing has been made.
The situation is now that the bike runs well over 2500 – 3000 rpm, and all the carburetors are fed fuel, although no 1 seems a bit rich. This is probably just a matter of pilot air screw adjustment. It takes the throttle well and is very smooth.
However, when the bike is warm, it will not idle below 3000 rpm. I have completely loosened the three throttle balancing adjustment screws and loosened the idle speed adjustment (see pic # throttle).
What am I doing wrong! The carburetors are entirely closed, and the idle speed is set to the lowest (the idle screw is free from the lever), yet the idle is very high when warm!!!! Can this be an issue with the pilot mixture screw, or did I assemble the linkage wrongly? I have included pictures of the throttle and choke linkage, and maybe someone has a clue. It seems like the throttle at no 4 is a slightly open adjustment (see pic # no 4), but this shouldn’t drive the idle speeds that high? I am completely out of solutions, and any advice is welcome
Cheers,
Hans
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the_big_h
Posts: 34
Joined: Thu Oct 01, 2015 7:35 pm
Location: Gads Hill, ON, Canada
Motorcycle: 1984 GL1200 Aspencade
1999 GL1500 Aspencade
1984 VF1100S Sabre

Re: Will not run below 3000 rpm after carburetor rebuild when warm

Post by the_big_h »

Yes, it is possible that #4 being slightly open can cause your high idle problem.
If you have (or can have) the carbs removed, you can to a "bench sync", using a strip of paper as a feeler gauge. Adjust the balancing adjustment screws and idle speed screw until there is a light drag pulling the strip of paper from between each of the throttle plate and the body.
Assuming the assembly is rigid enough to not disturb this adjustment as you assemble to the engine, this will give you a good starting point for balancing. The idle may be a bit high, but can be brought down with the idle speed screw.
Without doing a bench sync like this, if the balancing screws are way out of adjustment, one carb may end up holding others open too far.
If you don't want to remove the carbs, then you would need to sync them the usual way (with manometer or sync gauges), but it can be frustrating if you don't have a reasonable starting point.

The other things that could cause high idle are air inleak between the carbs and the engine (you can check by blowing some propane from an unlit blowtorch around the carb mountings, if it affects the idle at all then there is a leak in that area). One other possibility is if the choke plungers are not fully closing with the choke off.
User avatar
Hansmann
Posts: 8
Joined: Thu Aug 30, 2018 2:08 pm
Location: Copenhagen, Danmark
Motorcycle: 1982 GL1100A standard

Re: Will not run below 3000 rpm after carburetor rebuild when warm

Post by Hansmann »

I am not sure it the “invisible” opening on # 4 that makes problem. The idle screw is all that way out and completely free of the lever, and cannot be released any further. That is, even with idle screw completely release the engine runs wild. I would expect that with the throttle balancing screws fully release, and the idle screw all the way out, the engine would stall? New O-rings are installed and the seals between manifolds and engine are closing perfectly.
I have the carburettor out and I did wonder if anything associated to the chock or the linkage could be the root cause?
Thanks Hans
MattMcCoy
Posts: 71
Joined: Tue Aug 25, 2020 5:31 pm
Location: Fort Worth, TX, United States
Motorcycle: 1983 GL1100A Aspencade

Re: Will not run below 3000 rpm after carburetor rebuild when warm

Post by MattMcCoy »

I would:

Ensure the idle jets are clear and everything upstream is spotless.

Turn pilot jets 3 turns out.

Make sure the washers/springs on the linkage between each set of carbs are installed correctly. There should be a washer on each side.

Visually bench sync the carbs.

Check the o-rings between the heads and intake runners.

Tighten runners and band clamps when warm.

Synchronize the carburetors.


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