1976 GL1000 Tuning Post-Carb Overhaul


Information and questions on GL1000 Goldwings (1975-1979)
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spenray205
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Joined: Sun Dec 11, 2016 5:26 pm
Location: Dover, NH
Motorcycle: 1976 Honda GL1000

1976 GL1000 Tuning Post-Carb Overhaul

Post by spenray205 »



Recently overhauled the carbs on my GL1000. Ran rough before the rebuild with an unhealthy amount of backfiring, poor gas mileage, etc. Since rebuilding, I've gotten the carbs back on the bike and the sound and overall behavior are greatly improved. However, it has some issues that I'm trying to pinpoint the cause of...

1. The bike can idle well at 800-1100 RPMS, but when given just a little throttle (when fully warmed) it hesitates (loses some RPM's) before surging.
2. When giving it more than a "little" throttle, the RPM's surge and usually hang around 3000-4000 RPMS before coming back down. If not given a "little" throttle after coming back down, the bike will stall.
3. When fully warmed, after sitting for anywhere from 1-3 hours, the bike is nearly impossible to start.

Runs AWESOME above 2000-3000 RPMS.

For reference, here's a video of the bike with a carb sync tool hooked up exhibiting this behavior when given a "little" throttle:

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Top to bottom gauges represent carbs 2, 4, 3, 1.

Any ideas or advice would be helpful. Thanks!


GL_Steve
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Re: 1976 GL1000 Tuning Post-Carb Overhaul

Post by GL_Steve »

Were the carbs already synced in that video?

Have you checked that the belts/valve timing is correct?

Did you check valve lash.

Have good compression on all cylinders?

Know the proper sequence for syncing the carbs... adjust #1 to match 3, next adjust #2 to match 4, then adjust left side to match right side at the #4 carburetor...

Sounds like it is not completely warmed up yet, it takes a good 5-6 minutes to get it to good operating temperature just sitting idling and with some moderate revving.
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dingdong
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Re: 1976 GL1000 Tuning Post-Carb Overhaul

Post by dingdong »

And you need to do a more thorough sync. Not good.
spenray205
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Joined: Sun Dec 11, 2016 5:26 pm
Location: Dover, NH
Motorcycle: 1976 Honda GL1000

Re: 1976 GL1000 Tuning Post-Carb Overhaul

Post by spenray205 »

No, the carbs weren't synced. That video was taken after hooking the gauges up.
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spiralout
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Re: 1976 GL1000 Tuning Post-Carb Overhaul

Post by spiralout »

spenray205 wrote:No, the carbs weren't synced. That video was taken after hooking the gauges up.
Well, there ya go. Out of curiosity, since your gauges were hooked up, why did you not go ahead and synch them to see if that cured your problems before starting a thread about the problems that the synch might have fixed :shock:
Synching them will probably get rid of that little hesitation and maybe even the hanging idle. If the idle still hangs afterwards, use some propane or carb cleaner around the carbs (especially around the intake manifold to head area) to see if you can detect an air leak somewhere. It could be something as simple as a pinched manifold o-ring. An air leak can cause a hanging idle and an ignition problem can, too. If you can't pinpoint an air leak, check that your points gaps and ignition timing are dead on (which should really be done before trying to tune the carbs anyway) and that the mechanical advance behind the points plate is free and not sticking.
Like GL_Steve said, check your valve clearances but only when the motor is overnight cold.
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Aussie81Interstate
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Re: 1976 GL1000 Tuning Post-Carb Overhaul

Post by Aussie81Interstate »

Another video after synching will show up smaller problems - but they are out of whack where they are at the start of that video.

Here is a link to my photobucket account - there are two videos near the end that show before and after synching - they are not that good - but show how the bike reacts after they are pretty close..

http://s870.photobucket.com/user/81cust ... Interstate
spenray205
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Joined: Sun Dec 11, 2016 5:26 pm
Location: Dover, NH
Motorcycle: 1976 Honda GL1000

Re: 1976 GL1000 Tuning Post-Carb Overhaul

Post by spenray205 »

Had the chance to get it out again to get the sync right. This video was taken just before syncing 2 & 4 to 1 & 3. Getting them all matched up did not change the throttle response and tendency for the revs to hang and/or stay at 3000-ish rpms with no throttle response. Don't know if this is normal, but so much as touching any of the 3 sync screws makes the revs drop appreciably. Pilot-mix jets are set at 2 turns out.



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The throttle response is dead on when it's warmed up after 2-3 minutes. Take it around the block and let it really warm up though (fan turns on)... that's when it goes downhill. Because I had them lying around, I switched out the intake manifolds that were on the bike with a set with rubber in slightly better shape... didn't make a difference.


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