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Discussion Starter #1
Hi Folks

New user and owner here!

I bought an 81 GL1100 with 23000km on the clock.

It was standing for a while, so after buying it I bought carb kits and had all the carbs serviced and balance, so they all in sync.

The bike is running well until you get to high revs then there is a hesitation that almost feels like it is getting intermittent fuel or spark at high (5000+) revs. If you do not nail it and ride it more sedately then it runs well.

Another symptom is that carb 3 is running the plugs black, dry black soot not wet.

From my own research (Google and Youtube mechanic here) it should be either the carb running too rich, but then the plug will be wet as well, or the coil is not delivering sufficient spark, but we've swapped the coils around, and also replaced with another set and it remains plug no 3 that is black.

Any ideas to pass onto the mechanic will be greatly appreciated!

This is a brand new spark plug I pulled after riding for about 5km's.

323129
 

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I suspect the coils are at fault,my 82 did the same thing,was coils but you said you changed them?
 

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If you switched coils and its still the same cylinder, then its the carb. Simple.
carb can be running too rich for a lot of reasons.
Leaky needle and seat
Mis adjusted float
Sunk float
Dirt in the needle and seat.
There is a metering rod in the slide that could be in wrong.

Thinking about it, you could have 2 problems. If you want to beat on it and it does not respond, it could be lots of things.
If you back off on the throttle and it runs better, then its lack of fuel, like a plugged filter or pinched line.

If it just misfires after a certain RPM, then it could be spark related.
does this bike have points and condenser?

Does it matter if the tank is full or empty?

David
 

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It’s 1100 ,won’t have points
 

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You have a stopped up air jet under the slide and a kidney shaped plastic piece, goes to the main jet. I would almost guarantee it.
 

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Discussion Starter #7
I suspect the coils are at fault,my 82 did the same thing,was coils but you said you changed them?
I have used two sets of coils, the original and another used set. I do have another set here, but that is from a Volvo so need to work the wiring, might have to fit it just to test.

We have also swapped leads around to test, remains plug 3.
 

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Hi Folks

New user and owner here!

I bought an 81 GL1100 with 23000km on the clock.

It was standing for a while, so after buying it I bought carb kits and had all the carbs serviced and balance, so they all in sync.

The bike is running well until you get to high revs then there is a hesitation that almost feels like it is getting intermittent fuel or spark at high (5000+) revs. If you do not nail it and ride it more sedately then it runs well.

Another symptom is that carb 3 is running the plugs black, dry black soot not wet.

From my own research (Google and Youtube mechanic here) it should be either the carb running too rich, but then the plug will be wet as well, or the coil is not delivering sufficient spark, but we've swapped the coils around, and also replaced with another set and it remains plug no 3 that is black.

Any ideas to pass onto the mechanic will be greatly appreciated!

This is a brand new spark plug I pulled after riding for about 5km's.

View attachment 323129
You have to be careful, they can confuse you.
At first glance you might say rich. No doubt about it but you might be wrong.

A cylinder can run just lean enough that it lacks enough fuel to fire and make power. Then the gas that is in the combustion chamber can foul the plug because of the misfire. Not saying that is the case but just be aware,

Try creating a small vacuum leak to that cylinder. If things improve the engine is rich. Also try a little spritz of gas and if it comes to life that cylinder is lean. Clean the plug before testing
 

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If I had a dollar for everyone who came on a Forum and stated my engine is fine except ????? I would be at my villa in the Caribbean.
A cylinder with low compression can also cause that. Do a compression test first to get that off the table.
 

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Discussion Starter #10
If you back off on the throttle and it runs better, then its lack of fuel, like a plugged filter or pinched line.

If it just misfires after a certain RPM, then it could be spark related.
does this bike have points and condenser?

Does it matter if the tank is full or empty?

David
Thanks David, some answers.

Up to about 4000-4500 revs it seems fine, when you reach 5000 you feel the hesitation, it feel like somebody is holding the bike back, ease off the throttle and it goes away.

You have a stopped up air jet under the slide and a kidney shaped plastic piece, goes to the main jet. I would almost guarantee it.
We did the carb kit and also replaced the air cut all valves, that is all that was replaced in the carbs, but they were synchronized as well. I will have this checked out.

You have to de careful they can confuse you. At first glance you might say rich. No doubt about it but you might be wrong. A cylinder can run just lean enough that it lacks enough fuel to fire and make power. Then the gas that is in the combustion chamber can foul the plug because of the misfire. Not saying that is the case but just be ware,

Try creating a small vacuum leak to that cylinder. If things improve the engine is rich. Also try a little spritz of gas and if it comes to life that cylinder is lean. Clean the plug before testing
That this is very helpful, will get that done.

If I had a dollar for everyone who came on a Forum and stated my engine is fine except ?????
A cylinder with low compression can also cause that. Do a compression test first to get that off the table.
Compression test was done, good compression on all cylinders.
 

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Is it misfiring on one cylinder or is it losing power on all at 5000 RPM?

What you say sounds like it’s starving at higher Revs. Fuel volume could be holding you back. Whse is your fuel flow like?
David
 

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We did the carb kit and also replaced the air cut all valves, that is all that was replaced in the carbs, but they were synchronized as well. I will have this checked out.
A carb kit & air cut offs has nothing to do with it, that jet is fixed in place, is very small and easy to overlook. I have seen several with the same symptom and same problem.
 

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Discussion Starter #13
Is it misfiring on one cylinder or is it losing power on all at 5000 RPM?

What you say sounds like it’s starving at higher Revs. Fuel volume could be holding you back. Whse is your fuel flow like?
David
Does not feel like it is misfiring, no backfire either, cannot comment on fuel flow, actually have no idea how to test/check, but yes it definitely feels like it is not getting fuel at higher revs.
 

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A carb kit & air cut offs has nothing to do with it, that jet is fixed in place, is very small and easy to overlook. I have seen several with the same symptom and same problem.
Are these the pilot jets that you are referring to? Those were blocked when I got the bike.
They were all blocked, but now it is only that only plug that is showing black carbon.
 

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Are these the pilot jets that you are referring to? Those were blocked when I got the bike.
They were all blocked, but now it is only that only plug that is showing black carbon.
No it is not the pilot jets, again, remove the slide cap & the slide, remove the screw holding the little plastic kidney shaped cover, there is an air jet under it, it is plugged I will bet. You don't even have to pull the carbs.
 

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I have very little experience with the 1100 carbs but I did some work for a friend I worked with who owned an 83. That was years ago so I could be wrong. Between what I remember and what I found on the internet here is what I think.

I think Dave is referring to the primary air bleed jet. , The main (fuel) jet is supposed to deliver a mixture of air and gasoline to the engine, (an emulsion) If the air passage or the air orifice (air bleed hole/jet ) gets plugged the main jet can only deliver liquid gas instead of an emulsion. It doesn't take a lot of imagination to realize that running on gas alone will make the engine MUCH richer than an emulsion of air and gas. So.....when tou are in there if the air bleed looks fine clean it anyway. Also be sure the air passage from the air bleed to the emulsion tube is open.

Here is a picture I found and a link that might help/

323142
 

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I still think you have 2 problems.

#3 cylinder is too rich. Try the fix posted above. Check that the metering rod is in its correct spot and not bumped out of place.

For fuel flow, pull a line off a carb. Put the line in a clear jar or pop bottle. You might need to make it longer. Start the bike, See how many quarts or pints per minute. Rev the engine and see if flow increases or decreases.

There is a spec, I don't know it, but some one will pop in I hope and tell us.

I agree with some posts above. In 1978 when I was in school, I was told most carburetor problems are is the distributor. In this case since you swiched coil and no matter what you do, its still #3. I agree, its #3, not ignition.

David
 

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Just a couple other thoughts. I keep thinking if your pilot jets were plugged, other things could be plugged too, like fuel filter, or a restriction between tank and carbs.

ALSO I have seen it a few times in my life, exhaust can be partially plugged from sitting. This can cause loss of High RPM especially pulling up a hill, or any time you try to reach red line. The only way to test is pull the mufflers and drive it. You wilk know instantly if its the problem. We get plugged catalytic converters now and then. It is usually accompanied by intake backfire at high RPM, but not always.

We usually pull the O2 sensor and drive the car to see. I have seen it on old vehicles that sat for a long time. Worth checking into.
 
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