Gl1000 carbs


Information and questions on GL1000 Goldwings (1975-1979)
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Martinsyderob
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Gl1000 carbs

Post by Martinsyderob » Fri Jan 11, 2019 10:56 am



One for you smart techs out there.

I've got a gl1000 that's been stood a fair while and didn't run well at all.
I've stripped and cleaned the carbs with new rebuild kits.
Done all valves, put new coils and electronic ignition on it. Compression was good on all 4 cylinders.

When the bike is ideling it's smooth as a smooth thing but when you get to 2500rpm it starts to spit and miss, looking at the vac gauges it's only on cylinder 1 and the vacum is bouncing all over.
If I blank the 2 air valve holes off on top of the bank of carbs it stops the bouncing but it's like it's not letting the cv plunger move so I assume it's not lifting the needle?
Any thoughts?

Thanks

Rob



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Maz
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Re: Gl1000 carbs

Post by Maz » Fri Jan 11, 2019 1:57 pm

When you say "bouncing all over the place " are you referring to the vacuum guage needle? If so, I would suggest you close the valve on that gauge a touch, until the bouncing stops.
If you think the carb piston isn't lifting, it may be sticking in its chamber. When you cleaned the carbs, did you ensure that the pistons moved absolutely smoothly? They have to move perfectly smoothly.
If cylinder #1 has little or no vacuum, I would do a compression check to rule out a sticking valve.
Also, check for air leaks all around the carb joints and make sure the tiny 'O'ring in the air cut off valve on top of the carbs is present and correct.
Maz
Ironically, Common Sense is the LEAST common of all senses!

Martinsyderob
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Re: Gl1000 carbs

Post by Martinsyderob » Fri Jan 11, 2019 3:15 pm

Thanks for the reply. The damping on the vac gauges are fine and you can hear the engine poping and missing quite badly. The pistons were smooth it was only the pilots that were gummed up. Sprayed all round and can't find a leak, got 2 new o rings for the air valve.
Does the air valve hole at the front just go to the no1 cylinder?

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Maz
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Re: Gl1000 carbs

Post by Maz » Fri Jan 11, 2019 3:48 pm

It feeds all 4. I'm sure you know that its function is to richen the mixture on deceleration, which needs to be done on all 4 carbs.
I'm wondering if you still have some crap in one of the tiny passages in #1carb. You've probably read on here how scrupulously clean these carbs have to be and you really do have to clean, clean and clean again.
Any chance of checking with a Colortune to get a better idea of what's happening in the cylinders when the misfiring happens?
Maz
Ironically, Common Sense is the LEAST common of all senses!

Martinsyderob
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Re: Gl1000 carbs

Post by Martinsyderob » Fri Jan 11, 2019 4:15 pm

Miss happens at 2500 ish rpm and you can see it clear as a bell on the vac gauge, the needle drops off and comes back quickly. It's not ignition related as I've had the strobe light attached to that cylinder and it's sparking fine.
I assume the piston in the carb is jumping up and down and when I blank the hole off it stops the piston moving or holds it wide open?

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Maz
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Re: Gl1000 carbs

Post by Maz » Fri Jan 11, 2019 4:27 pm

Martinsyderob wrote:
Fri Jan 11, 2019 4:15 pm
Miss happens at 2500 ish rpm and you can see it clear as a bell on the vac gauge, the needle drops off and comes back quickly. It's not ignition related as I've had the strobe light attached to that cylinder and it's sparking fine.
I assume the piston in the carb is jumping up and down and when I blank the hole off it stops the piston moving or holds it wide open?
The strobe will show you that the coil is working (but not necessarily that the plug is sparking), but a colortune will let you see the combustion in the cylinder (or not, when it misfires!) and get an idea from the flame colour of what the mixture is doing.
Your thoughts on the carb piston can be checked with a mirror in the 'plenum' chamber if you run the engine without the air filter.
Maz
Ironically, Common Sense is the LEAST common of all senses!

Martinsyderob
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Re: Gl1000 carbs

Post by Martinsyderob » Sat Jan 12, 2019 4:01 am

Thanks

Not got access to a colortune so will have to stick to the strobe light. I'll try the mirror and see what's happening. Any ideas why when I blank the air valve holes off it stops the vacuum on that cylinder.

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Maz
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Re: Gl1000 carbs

Post by Maz » Sat Jan 12, 2019 7:03 am

I can't explain that.
I'm hoping 'Old Fogey' will read your thread, as he owns Wingovations and knows these carbs inside out and upside down. It may be worth sending him a PM directly with your problem.
Maz
Ironically, Common Sense is the LEAST common of all senses!

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terryt
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Re: Gl1000 carbs

Post by terryt » Sat Jan 12, 2019 11:28 am

Sounds like valve bounce. recheck the valve gap. also swap no one spark plug with no two plug it could be breaking down load

Martinsyderob
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Re: Gl1000 carbs

Post by Martinsyderob » Sat Jan 12, 2019 1:25 pm

I've checked the valves but will recheck alothough I don't think valve bounce at 2500rpm would happen. Had 2 new sets of plugs in it so far but I will swap them around. Can't understand why when you block the holes of the air valve off it stops the the cylinder pulling on the vac gauge. Is seems the piston in the carb is staying down or up ( not been near the bike today) and it's only that cylinder as the others are fine and working well.

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terryt
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Re: Gl1000 carbs

Post by terryt » Sat Jan 12, 2019 1:53 pm

When you rebuilt the carbs did you polish the sliders and dash pot. also set the float level height.

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ekvh
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Re: Gl1000 carbs

Post by ekvh » Sat Jan 12, 2019 3:18 pm

Smooth at idle, starts missing at 2500, sounds like slide isn’t lifting up.

Martinsyderob
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Re: Gl1000 carbs

Post by Martinsyderob » Sat Jan 12, 2019 7:08 pm

These are the things I'm looking for as what to look at, I polished the slides and they moved free with a small amount of suction resistance(all 4 seemed the same) by dash pot I assume you mean the body it slides in?

What do you think would cause the lack of lift?
I think I'm getting a bit of lift with the vac gauge needle jumping at 2500 and then it drops down again? Seems to be lifting and dropping fairly quickly so where would you expect I'd be loosing the vacum?

Thanks for the comments.

Rob

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ekvh
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Re: Gl1000 carbs

Post by ekvh » Sat Jan 12, 2019 8:05 pm

You probably have checked this, but sometimes (rarely) people have found burrs on the carb throat (venturi area) that the slide moves up and down in.

Run your finger along each edge and see if there’s a rough spot enough to be causing the slide to lag. Also the brass “tooth” that protrudes to align the shaft.

kndw
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Re: Gl1000 carbs

Post by kndw » Sun Jan 13, 2019 4:30 am

+1 on the slides.

I've had a similar problem, whrre the bikr would idle fine and also run well except at ~2500 rpm. I found the slide on one cilinder to be sticking just a tiny bit. After proper cleaning and polishing it was resolved.

Martinsyderob
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Re: Gl1000 carbs

Post by Martinsyderob » Sun Jan 13, 2019 8:28 am

Good stuff, looking like it's pointing at the slide then. I'm working away till mid week so I'll have a good look at it again when I get home and report back.

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Fred Camper
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Re: Gl1000 carbs

Post by Fred Camper » Mon Feb 04, 2019 10:15 pm

Slides need to move free when near horizontal. Not good enough if the slide vertically.

Old Fogey
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Re: Gl1000 carbs

Post by Old Fogey » Sun Mar 10, 2019 4:47 pm

Also, check the plastic buttons for hairline cracks. It doesn't take much to lose the vacuum through a crack.
'Impossible' is just a level of difficulty! The only stupid question is the one you didn't ask first!

( Seriously, you haven't read all 115 pages of my http://www.wingovations.com website ?? :shock: )

Old Fogey
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Re: Gl1000 carbs

Post by Old Fogey » Tue Mar 12, 2019 9:27 am

I'm a little confused when you say 'blank off the two air valve holes'. Are you removing the air cut off valve to do this? If so, why? The valve only comes into play under deceleration ie. high vacuum condition, to richen the mixture to eliminate popping or backfiring in the exhaust.


'Impossible' is just a level of difficulty! The only stupid question is the one you didn't ask first!

( Seriously, you haven't read all 115 pages of my http://www.wingovations.com website ?? :shock: )

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