Slow throttle response......... HELP!!


Information and questions on GL1000 Goldwings (1975-1979)
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Theo331
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Motorcycle: 1978 GL1000
1981 GL1100(Basketcase)

Slow throttle response......... HELP!!

Postby Theo331 » Thu Jan 23, 2014 2:35 am



I have a 78 Oldwing that sat for a while before I acquired it. I have done a lot of little things to her, but I am not sure which way to go with this problem: when riding the bike, the bike idles fine. However the throttle seems to lag when I twist it up the bike stays at idle, then shoots up to 3000 rpm as the throttle is twisted up further. The linkages all move fine. Supposedly the carbs were gone through, but I suspect not well. Is this the right path to pursue? The bike is currently running on a mixture of 87 octane with a healthy dose of Seafoam added. I have already replaced the plugs, since they were all worn, and did not all match. They were a mix of da7's and da8's.

This is my first foray into fixing my own ride, and I could use some guidance............ Thanx!


Whatever doesn't kill you, only makes you stronger!

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dingdong
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Re: Slow throttle response......... HELP!!

Postby dingdong » Thu Jan 23, 2014 7:52 am

Yes, it is probably the carbs in need of a proper rebuild. However the symptoms could also point to the mechanical timing advance, behind the points, binding.
Tom

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virgilmobile
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Re: Slow throttle response......... HELP!!

Postby virgilmobile » Thu Jan 23, 2014 8:57 am

Hmmm...I'm not so sure bout the mechanical advance....it really doesn't move till the rpm's are gettin up there.(1500 RPM)....altho it's worth looking at while the "split the difference" point timing is done...

I'd be more inclined to be looking at the slides in the carbs....there often overlooked as far as how well they move...just a little binding will certainly dog the engine...those slides must float butter smooth and I always use a shop vac to test them before I put the carbs back on...
Adjust the valves "by the book".
Sync the carbs as the last step....

Lastly,I believe the carbs may still have "composite" floats...my 78 did..they would absorb fuel and sink,raising the fuel level and enriching the fuel mixture till the plugs ran sooty....A few dips in Polyurethane fixed this...

So pull a couple of plugs and scrutinize them...they tell a lot about how the endine is running....
There's even a "how to" about reading your plugs...

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WingAdmin
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Re: Slow throttle response......... HELP!!

Postby WingAdmin » Thu Jan 23, 2014 9:26 am

If you are twisting the throttle open relatively quickly, and it is lagging before jumping up, it could be a bad/clogged accelerator pump/circuit. If it happens also when you open the throttle slowly, then probably not the accelerator pump.

Theo331
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Motorcycle: 1978 GL1000
1981 GL1100(Basketcase)

Re: Slow throttle response......... HELP!!

Postby Theo331 » Thu Jan 23, 2014 2:00 pm

The slow response is noticed more when slowly bringing up the rpm's. For example you are first starting off from a stop, the throttle seems to do nothing, but the linkage definitely moves during this, when the throttle is turned enough to reach 3000 rpm the bike suddenly springs to life. This of course makes it interesting to take off on the dirt/gravel parking lot at my apartment complex.
Whatever doesn't kill you, only makes you stronger!

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virgilmobile
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Re: Slow throttle response......... HELP!!

Postby virgilmobile » Thu Jan 23, 2014 2:34 pm

I don't recall that the carbs on the 78 had a accelerator pump......more investigation is in order...
If it does,it would be attached to the right rear carb...a arm operates it with the throttle.....

It is possible that ,even tho it seems to idle OK,there may be a carb problem....in the slow jets...

Here's a quick test...with a cold engine...start it...keep the rpm as low as possible..(1000 rpm)..
try not to get it above 1200 rpm...run it for 6 seconds only and shut it off...
Lightly tap each header...they should be equally warm...
I have actually seen a gl1000 idling on one cylinder..Sounded a bit funny..the idle jets were plugged on the other 3....
Open the throttle and in a short time the other cylinders would get gas from the main jets and take off..Zoom...
When the engine is just right,timing correct and carbs synced,you can let the clutch out slowly at a idle without stalling,twist the throttle wide open and it will climb in rpm smooth and unreasonably fast.
My 78 went from idle to red line in 2 heartbeats...

Theo331
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Location: Mesa, AZ
Motorcycle: 1978 GL1000
1981 GL1100(Basketcase)

Re: Slow throttle response......... HELP!!

Postby Theo331 » Thu Jan 23, 2014 5:01 pm

Thanx guys, i appreciate the help, never worked on multiple carbs before...
Whatever doesn't kill you, only makes you stronger!

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Fred Camper
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Re: Slow throttle response......... HELP!!

Postby Fred Camper » Thu Jan 23, 2014 5:35 pm

There is no accelerator pump on a 1978, that came in with the 1100. Sure sounds like sticky sliders in one or more carbs to me. The sliders need to be silky smooth, as it is only a slight change in vacuum that needs to move them. The 1100's got rid of the pesky sliders and went with a diaphragm if I recall correctly.

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virgilmobile
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84 GL 1200 I

Re: Slow throttle response......... HELP!!

Postby virgilmobile » Thu Jan 23, 2014 8:02 pm

Use your other glasses. :lol: my 83 gl1100 had the same style of slide as the 1000.My 84 gl1200 used a diaphragm on top of the slide.

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djoyner
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Re: Slow throttle response......... HELP!!

Postby djoyner » Sat Jan 25, 2014 8:00 pm

I had a similar problem on my '78 Gl1000. A carb sync and a new air filter took care of the issue.
D J
2006 VTX 1300S
1978 GL1000
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Nickel1
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Re: Slow throttle response......... HELP!!

Postby Nickel1 » Wed Feb 12, 2014 11:51 am

I am not sure how this will effect the conversation, but I have a single carb on my 78 GL1000, and I have to dance the throttle to get it to take off as well??
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virgilmobile
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84 GL 1200 I

Re: Slow throttle response......... HELP!!

Postby virgilmobile » Wed Feb 12, 2014 12:36 pm

I have a single carb on my 78 GL1000, and I have to dance the throttle to get it to take off as well??


If I read this correctly,with the single carb conversion you also have a delay response throttle??

If so,consider this...
The fuel feed (idle/mid and main jet ) from the original carbs were about 1/4 to 1/3 of the distance to the intake valve than with the single carb conversion....Measure it...I "think" Im close..
Better throttle response is the ability of the fuel system to provide the correct fuel mixture at the moment it's needed....Eg .multiport fuel injection systems.

I think with the 'conversion' the fuel has a much longer travel (and volume)to get inside the cylinders than the 4 carb method.As one cylinder draws air,It's having to draw from the box and the other 3 tubes as well...theres a lot of volume there...The single carb use has very little volume before the fuel jets.

Personally I believe that the engine draws much more idle mixture volume from the plenum box before it gets to the richer mixture(the lag time) compared to 4 carb system..
Each carb per cylinder has a very low amount of volume to consume before it gets the rich blast of air.
This is as close to fuel injection as you can get with a carb system....
Remember the old VW conversion??? I took the single carb off (long intake tubes too) and installed Weber carbs,one on each head...What a difference that made....

Is there a fix.???
Possibly reduce the volume capacity of the plenum box...A "insert" not only to reduce the volume but direct airflow from the carb to the down tubes instead of just dumping the fuel into a metal box to be sucked in...

How bout a fuel injector...one for each intake..only operated when the throttle is twisted...My 78 Mercedes used a Lucas EFI system that had multiport fuel injectors PLUS one in the intake instead of a accelerator pump...it would "tick"and squirt a bit of fuel every time the throttle was pushed down...

How much time and money is it worth to re-engineer this...????? Or just live with it.

As always...This is theoretical based on experience,practical operation and general knowledge of the requirements of a engine to run well...

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CaptainMidnight85
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Re: Slow throttle response......... HELP!!

Postby CaptainMidnight85 » Fri Jan 13, 2017 3:15 pm

Nickel1 wrote:2013-09-15 10.24.42.jpgI am not sure how this will effect the conversation, but I have a single carb on my 78 GL1000, and I have to dance the throttle to get it to take off as well??

Nothing you do will "fix" that manifold.
There will ALWAYS be considerable condensation problems when allowing 90° surface angles within Any fuel tract.
Add the fact of no applied heating to the plenum and runners to create a boundary layer for the fuel charge to ride on and your symptoms are typical of most every conversion with no solution other than false claims of carburetor calibration to compensate.
Use of a **HEATED** and Professionally designed plenum with integrated runners designed for optimum, unimpeded flow to the cylinder head port opening is the only viable solution for a conversion manifold. Weber advises ALL not to construct their own manifolds for the exact symptoms/results that you are experiencing and describing. These problems are inherent to your "manifold" design and not correctable as-is.

The heated conversion manifold below is the best alternative for a single carburetor conversion with a GL1000 engine.

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Re: Slow throttle response......... HELP!!

Postby WingAdmin » Fri Jan 13, 2017 4:15 pm

CaptainMidnight85 wrote:
Nickel1 wrote:2013-09-15 10.24.42.jpgI am not sure how this will effect the conversation, but I have a single carb on my 78 GL1000, and I have to dance the throttle to get it to take off as well??

Nothing you do will "fix" that manifold.
There will ALWAYS be considerable condensation problems when allowing 90° surface angles within Any fuel tract.
Add the fact of no applied heating to the plenum and runners to create a boundary layer for the fuel charge to ride on and your symptoms are typical of most every conversion with no solution other than false claims of carburetor calibration to compensate.
Use of a **HEATED** and Professionally designed plenum with integrated runners designed for optimum, unimpeded flow to the cylinder head port opening is the only viable solution for a conversion manifold. Weber advises ALL not to construct their own manifolds for the exact symptoms/results that you are experiencing and describing. These problems are inherent to your "manifold" design and not correctable as-is.

The heated conversion manifold below is the best alternative for a single carburetor conversion with a GL1000 engine.
manifold_2 022_zpsohycrnxh.jpg


You got it. This is 100% correct. The problem only gets worse as the ambient temperature drops, and the cool air flows around the intake runners, taking away what little engine heat has migrated into them.




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