Off-idle stumble

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MtnMan

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Boulder County, Colorado, USA
Hello,

My new to me 1981 GL1100 Standard (~28,000 mls) starts, idles and runs very well with the exception of an off-idle stumble at low throttle openings. It always runs well at larger throttle openings (> ~40%).

It feels like it is not getting enough fuel off-idle, but I might be wrong.

The previous owner who has quite a bit of Goldwing knowledge, has told me that he just cleaned the carburetors before I got this bike. Before he got it it sat for some time so maybe there is still some varnish in the carbs left.

I ran three tanks of gas with Seafoam through the carbs which did not help, put in new plugs, which, as expected, didn't help either.

I tried Starting Fluid around the intakes, which did not affect rpms.

I am planning also to check the slides; perhaps one of them is not moving freely.

I also connected vacuum gauges and the carbs seem to be well synchronized.

I have read the the vacuum advance could cause the stumble, but can this engine run smoothly at higher rpm's (>~3,500) and larger throttle openings when the vacuum advance does not work properly?

I would appreciate any advice!

Armin
 
MtnMan":1vy5cze3 said:
but can this engine run smoothly at higher rpm's (>~3,500) and larger throttle openings when the vacuum advance does not work properly?
Click to expand...

It could, for sure...depends on if the advance mechanism is stuck, and if so, in what position. From what I've learned here, tho, seems like most of the off-idle stumbles usually winds up being a carb issue.
Others with way more knowledge will chime in. :good:
 
slabghost":3uk3bd6o said:
Check your vacuum advance. If it's bad you have the wrong timing and an air leak.
Click to expand...

Thank you for your quick responses! I don't want to take short cuts, but do I have to remove the rear wheel and swing arm to do the test?

Is there any other way I can test the vacuum advance? Could I use a timing light?

Armin
 
I used a MightyVac hand vacuum pump to check mine. You can reach the vacuum advance canister from the right side of the bike. If it's bad at least plug the vacuum line and it will run okay.
 
It could be the vacuum advance for sure, but I would be more inclined to think clogged carbs. Even though they may have been cleaned, they may not have been completely cleaned (not uncommon).

Also, if the floats are not set right you can have a very similar issue.
 
:good:
mcgovern61":1j1mgip0 said:
It could be the vacuum advance for sure, but I would be more inclined to think clogged carbs. Even though they may have been cleaned, they may not have been completely cleaned (not uncommon).

Also, if the floats are not set right you can have a very similar issue.
Click to expand...
:good:
Absolutely. Just pointing out a problem that I overlooked far too long which is an easy check.
 
slabghost":16gfvvyg said:
I used a MightyVac hand vacuum pump to check mine. You can reach the vacuum advance canister from the right side of the bike. If it's bad at least plug the vacuum line and it will run okay.
Click to expand...

Thank you! I am still trying to understand how a faulty vacuum advance (or its effect) can be fixed by plugging the vacuum line.
I think I read that there is also a mechanical advance. If this is true, why are there two advance mechanisms?

Would I see it with a timing light if the advance wouldn't work properly?

Armin
 
if its bad ...the vacume canister ,,,then essentaly you have direct vacume leak that effects the carbs too ...plugging the line fixes vacume leak on carbs ....dosent fix the vacume cylinder at all ...but there is also a machanical advance system also ...so as long as its and moves right you dont loose that part of the advance ....hope i explaned that right sometimes im hard to understand
 
MtnMan":3n5d1501 said:
slabghost":3n5d1501 said:
I used a MightyVac hand vacuum pump to check mine. You can reach the vacuum advance canister from the right side of the bike. If it's bad at least plug the vacuum line and it will run okay.
Click to expand...

Thank you! I am still trying to understand how a faulty vacuum advance (or its effect) can be fixed by plugging the vacuum line.
I think I read that there is also a mechanical advance. If this is true, why are there two advance mechanisms?

Would I see it with a timing light if the advance wouldn't work properly?

Armin
Click to expand...
Plugging the vacuum line only fixes the air leak as explained above. Yes it has a mechanical advance too. Not sure why engineers decided to use both mechanical and vacuum advance. But they did and it will run okay on just the mechanical. Maybe it was because of the off idle stumble? No idea if it can be seen with a timing light or what to look for.
 
a good chance realy these ignitions are rather good on the electronics ..as in pluse generators ..they do go out some ....but wires.... plug end caps.....and coils go sub par alot ...there thirty plus yrs old...and are not no where as tuff as the wing motors ...carbs and ignitions sould be brought up to par on any new to you oldwing
 
joedrum":2oz56t2n said:
a good chance realy these ignitions are rather good on the electronics ..as in pluse generators ..they do go out some ....but wires.... plug end caps.....and coils go sub par alot ...there thirty plus yrs old...and are not no where as tuff as the wing motors ...carbs and ignitions sould be brought up to par on any new to you oldwing
Click to expand...

I want my bike to be healthy and reliable...

Can you please give me a recommendation for high quality coils, wires and plug end caps?

Armin
 
hmmmmwell 1 buy irridium plugs...2 call dyna get the teck guys on ..tell them exactly what you have ...as in yr of bike and assesories like radio or not ...they can set you up with a coil thats right for your bike ....and get the wire set too ..that works with the coils they will be complete with ends and then write every thing down ...and post here so we can look at it and check it out to conferm it all sounds right ...if it dose ...buy it ....there a web site i think z1 enterprises that handles dyna stuff ...im not good emough on puter to paste it myself ...but thats what id do its hard to beat dyna coils or service
 
I think you could still have a problem with the carbs. Stumbling can be caused by a miss alignment of the pilot screws and you could get a rather close vacume sync, but the vacume won't come all the way between 10 and 15 on the vacume gage.
 
Sir you have a 81 and it has slow jets that are pressed in, you might need to pull them and clean them to achieve your goal of a smooth take off.
 

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