Carb surging


Information and questions on GL1500 Goldwings (1988-2000)
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TJ-GL1500
Posts: 17
Joined: Sun Jan 24, 2016 9:32 pm
Location: Durham, NC
Motorcycle: '88 GL1500

Carb surging

Postby TJ-GL1500 » Mon Apr 04, 2016 11:57 am



Hey all!

I recently rebuilt both carbs on my gl1500. I just reinstalled them today.

The bike idles great, but after rolling the throttle and releasing it, the bike stays up around 2k rpms without any throttle input. It will stay there for a few seconds, then slowly drop down to normal idle.

Any idea what might be causing this?



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virgilmobile
Posts: 7647
Joined: Sun Sep 19, 2010 5:39 pm
Location: Denham Springs,La.
Motorcycle: 1988 GL1500 I
Previously owned
78 GL1000
81 GL1100
82 GL1100 I
83 GL1100 I
83 GL1100 standard
84 GL 1200 I

Re: Carb surging

Postby virgilmobile » Mon Apr 04, 2016 8:27 pm

2 possibilities..or 3.
take the air cleaner back off and look at the linkage for the choke and throttle.Be sure they return to there stops.Especially the choke.Watch for cable routing on the choke...if binding(wrong place),it can leave it open just a bit.The return spring isn't very strong for it.
While your there,start the bike,pop the throttle a couple of times to 4000rpm and watch both slides..Be sure they open and close promptly.
When you close the throttle,the slides should drop like a rock and starve the engine for air(vacuum goes very high)..The rpm should drop pretty fast with it.
By the way..did you look at all the known vacuum line problems..one under the black mat and a bunch on the carb and intake pipes for heat damage or deterioation .Mostly the ones with a sharp 90°bend.

TJ-GL1500
Posts: 17
Joined: Sun Jan 24, 2016 9:32 pm
Location: Durham, NC
Motorcycle: '88 GL1500

Re: Carb surging

Postby TJ-GL1500 » Tue Apr 05, 2016 7:38 am

Also, I recently discovered that when I slam the throttle, after the accelerator pump has done its duty and I'm holding the throttle open, the motor sputters and rpm fluctuates from about 3-5k without any change in throttle. Might these two problems be interrelated?

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virgilmobile
Posts: 7647
Joined: Sun Sep 19, 2010 5:39 pm
Location: Denham Springs,La.
Motorcycle: 1988 GL1500 I
Previously owned
78 GL1000
81 GL1100
82 GL1100 I
83 GL1100 I
83 GL1100 standard
84 GL 1200 I

Re: Carb surging

Postby virgilmobile » Tue Apr 05, 2016 9:24 am

In a word..Yup.
Being a dual carb system,if one is delivering fuel unequal to the other,the engine will hunt for fuel,drawing fuel as needed for each side as necessary.I actually watched this happen on mine on the main jets.

TJ-GL1500
Posts: 17
Joined: Sun Jan 24, 2016 9:32 pm
Location: Durham, NC
Motorcycle: '88 GL1500

Re: Carb surging

Postby TJ-GL1500 » Tue Apr 05, 2016 9:28 am

So what I'm walking away with is this-

I need to check the throttle and choke mechanisms for correct operation, check my vacuum lines for kinks bends holes and pinches, and sync the carbs as best I can.

Am I missing anything?

User avatar
virgilmobile
Posts: 7647
Joined: Sun Sep 19, 2010 5:39 pm
Location: Denham Springs,La.
Motorcycle: 1988 GL1500 I
Previously owned
78 GL1000
81 GL1100
82 GL1100 I
83 GL1100 I
83 GL1100 standard
84 GL 1200 I

Re: Carb surging

Postby virgilmobile » Tue Apr 05, 2016 11:15 am

The vacuum lines should have been checked when the carbs were off the bike,sorry.
One of them is under the carb insulating mat.The others are front and rear of the carbs.Really difficult to get to when there mounted.
Bout all you can do is check the throttle and choke functions and watch the slides.
If they are perfect then go at the vacuum lines.
Pay close attention to the vacuum lines where they"T" off the right side and go into the right faring.I did have one come loose after I put my carbs back on.
Don't forget to tighten the clamps holding the carbs to the insulators.
Syncing is not a best guess.It really needs to be done with your choice of instrument.
They can be made by hand or purchased.

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RBGERSON
Posts: 2612
Joined: Tue Mar 09, 2010 7:57 am
Location: SCOTTSDALE, AZ
Motorcycle: 98 SE GL 1500
had every year from 75 to 83

Re: Carb surging

Postby RBGERSON » Thu Apr 07, 2016 7:24 am

If you can get a straw under the carbs from the side or front..and spray some starter fluid or similar flammable and she surges most likely a vacuum tube sucking it in..IE carbs off again and replace all the tubes...while you are at it...sorry.


HAD LOTS OF GOLDWING 75-83
NOW INTO 1500'S..RIDING A 1998 SE

FAIR WINDS,
RB


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