Carb? Vacuum? Fuel delivery?


Information and questions on GL1500 Goldwings (1988-2000)
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bri720a
Posts: 64
Joined: Mon Oct 12, 2020 3:20 pm
Location: United States
Motorcycle: 96 GL1500SE & 03 VTX1800r

Carb? Vacuum? Fuel delivery?

Post by bri720a »



98 1500se it had sat for a few years at least.
I purchased, pulled motor to replace starter idle gear, soaked and rebuilt carbs, new jets, slides, manifold boots etc., rebuilt petcock, replaced vacuum lines.

It idles beautifully, with bike sitting, at about 3000 rpm there is a bit of a surge. While riding/under load, it will do good under about 2000rpm. Anything more and it stumbles and loses power. Opening the throttle more then 1/6 or so it stumbles and bogs. And will not get above about 3000 rpm. If I really work it I can get it a bit more but there is still no power. With choke on it does a bit better but not great. Obviously it is a fuel issue. But what should be my first thing to go back to be?

I am very mechanical but honestly not much experience with carbs. I have not adjusted them beyond the initial setting of 2 turns out of air/fuel mixture. I am having a very difficult time getting the D socket on the mixture screw to adjust. Could that still be the issue? I have not balanced them yet either. Seems like that would be more of a fine tune than what I am dealing with. I could be wrong though, I was under the impression the air/fuel was more to do with at idle and balancing will gain correct power etc.

Thanks for your wisdom!


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Swagonmaster
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Location: Stokesdale, NC
Motorcycle: 1990 gl1500 SE

Re: Carb? Vacuum? Fuel delivery?

Post by Swagonmaster »

There are a ton of things that can affect running so let's see:

fuel pump and/or filter
float level in the carb
installing the carb diaphram incorrectly, it positions the air slide
there is a spagetti bowl full of vacuum hoses, you may not have gotten the
right one (you didn't put one in the wrong place or fail to hook one up did
you?)
air filter, since it's on top I assume it's ok
spark plugs possibly but usually doesn't have that great an effect
lets not forget the timing belt adjustment
restricted exhaust, unlikely but you know

First thing I'd do is listen for vacuum leaks and CAREFULLY spray some throttle body cleaner at the parts in the intake to see if there are any air leaks you can't hear, the engine speed will go up if you spray an air leak, spray will burn if you have a plug wire sparking.
Other than that I'd have to think awhile.
Try to learn from the mistakes of others..... you won't live long enough to make them all yourself!
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ct1500
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Location: Glastonbury,CT
Motorcycle: 1988 GL1500
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Re: Carb? Vacuum? Fuel delivery?

Post by ct1500 »

At two turns out the mixture screws should be in the neighborhood to run halfway decent. A lean mixture from idle screw setting would be more noticeable at idle rather than the 3000RPM range. If the bike is stationary and stumbling at 3000RPM with slow roll on of throttle then that points to the carbs main circuit not supplying the needed fuel or a problem with fuel pump or vacuum petcock. The slides are secondary mains that open and supply more fuel under high engine demand/load.
Check your fuel pump for decent flow and that it can generate 1.5psi when running. Check your petcock with a vacuum pump that it can hold a vacuum and that it opens for good fuel flow through it and that you indeed have manifold vacuum available to petcock with engine running.
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bri720a
Posts: 64
Joined: Mon Oct 12, 2020 3:20 pm
Location: United States
Motorcycle: 96 GL1500SE & 03 VTX1800r

Re: Carb? Vacuum? Fuel delivery?

Post by bri720a »

Thank you! I will check those out in the morning. The I am guessing the slides are sticking, :(
I will also check the other stuff while I'm at it.
bri720a
Posts: 64
Joined: Mon Oct 12, 2020 3:20 pm
Location: United States
Motorcycle: 96 GL1500SE & 03 VTX1800r

Re: Carb? Vacuum? Fuel delivery?

Post by bri720a »

The slides were definitely sticking. Buffed the bores some Scotch-Brite. I also believe the diaphragms were not sealing correctly. When I put the first one back together I remembered how they should close someone slowly and the particular vacuum sound they make.
Thank you for your help!


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