Not returning to idle.


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badandy
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Motorcycle: 1977 GL1000 Goldwing
1982 GL500I
1983 VT500 Shadow

Not returning to idle.

Post by badandy » Wed May 03, 2017 8:20 am



My GL1000 will not return to idle without help. The carbs have been rebuilt and synchronized, new points and timing set using the split timing method. The carb linkage and throttle cables are not binding, but when the idle doesn't return I can push the linkage at the carb butterflies just a bit and it settles down. I have added two small tension springs where the linkage is attached to the butterflies and it does the trick. Not the correct fix.

I am wondering if my little nylon pivot bushings on the linkage arms are worn out. There seems to be more play on one bank than the other. There are no leaks or play where the butterfly shafts go through the carb bores. Just seems that there is not enough tension on the main linkage arms to pull the carbs completely closed.

If I snap the throttle fast is settles right to idle speed, but easing the throttle on and letting go it stays at about 2k. The main return spring is attached correctly. I tried to increase the torque force by loosening the nut and turning the spring. It will move very little and that didn't make a difference.

Anyone have similar issues?



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dingdong
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Re: Not returning to idle.

Post by dingdong » Wed May 03, 2017 10:00 am

Even if the bushings are worn the torsion springs around the butterfly shafts should return the linkages to the proper home position. I suggest that you have something binding either at one of the butterfly assemblies or the linkage where it connects to the bell crank. The torsion springs can become weak also. (see your addition of a spring) That would keep the assembly from properly returning to the home position. Are you sure that everything is assembled properly? Did you do the re-build or someone else do it?
Tom

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badandy
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Motorcycle: 1977 GL1000 Goldwing
1982 GL500I
1983 VT500 Shadow

Re: Not returning to idle.

Post by badandy » Wed May 03, 2017 11:23 am

I did the rebuild using Randakk's kit. It had the same issue before the rebuild and I checked everything while the carbs we're apart. No binding anywhere.

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Maz
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1976 CB500T
1979 CB750L
1990 Yamaha FJ1200
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Re: Not returning to idle.

Post by Maz » Wed May 03, 2017 3:23 pm

badandy wrote:My GL1000 will not return to idle without help. The carbs have been rebuilt and synchronized, new points and timing set using the split timing method. The carb linkage and throttle cables are not binding, but when the idle doesn't return I can push the linkage at the carb butterflies just a bit and it settles down. I have added two small tension springs where the linkage is attached to the butterflies and it does the trick. Not the correct fix.
If you have the early carbs with

I am wondering if my little nylon pivot bushings on the linkage arms are worn out. There seems to be more play on one bank than the other. There are no leaks or play where the butterfly shafts go through the carb bores. Just seems that there is not enough tension on the main linkage arms to pull the carbs completely closed.

If I snap the throttle fast is settles right to idle speed, but easing the throttle on and letting go it stays at about 2k. The main return spring is attached correctly. I tried to increase the torque force by loosening the nut and turning the spring. It will move very little and that didn't make a difference.

Anyone have similar issues?
If you have the early round linkage rods with the spring joint ends, there may be some play in these joints. It's well worth modifying these joints to get rid of the springs. Take a look at the Technical Tips section on the Wingovations.com website for a detailed description of the modification.
Maz
Ironically, Common Sense is the LEAST common of all senses!

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badandy
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1982 GL500I
1983 VT500 Shadow

Re: Not returning to idle.

Post by badandy » Wed May 03, 2017 3:56 pm

I have the flat linkage.

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badandy
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1982 GL500I
1983 VT500 Shadow

Re: Not returning to idle.

Post by badandy » Wed May 03, 2017 7:13 pm

I think I have found the issue. I have excessive vacuum leaks around the throttle shafts. So much to the point I can stall the engine while spraying carb cleaner around the shafts on one bank and adversely affect the idle on the other. Going to pull the shafts and see what I can find. The felt seals are probably gone.

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Maz
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Re: Not returning to idle.

Post by Maz » Thu May 04, 2017 1:44 am

badandy wrote:I have the flat linkage.

Well that ain't the problem then! :)
Maz
Ironically, Common Sense is the LEAST common of all senses!

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badandy
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Re: Not returning to idle.

Post by badandy » Thu May 04, 2017 7:18 am

Doing another sync on the carbs gave it away while I scratched my head asking myself what is wrong. Every time I would touch the sync screws the idle would fluctuate before I even got a turn on them! I was actually moving the shafts enough to create a worse leak. The small tension springs I added kept the shafts pulled tight in one position that I could adjust the idle and do a sync to the consistent leak at that point. Adjusting the pilot air screws have no effect due to the leaks. I left them at the 2 1/2 turns in the manual.

I can actually ride it like this, but I am not happy with it. Definitely leaning out at idle. It runs fantastic other than the idle issue! I hope I can salvage the newly rebuilt carbs. I have about $200 in them and they look like new!

I have rebuilt a lot of carbs and never had ones with this problem. I am beginning to wonder if these are the original carbs (746A). The bike only has 37k on it.

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Maz
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Re: Not returning to idle.

Post by Maz » Thu May 04, 2017 7:41 am

badandy wrote:I think I have found the issue. I have excessive vacuum leaks around the throttle shafts. So much to the point I can stall the engine while spraying carb cleaner around the shafts on one bank and adversely affect the idle on the other. Going to pull the shafts and see what I can find. The felt seals are probably gone.
I believe I'm correct in saying that the felt 'seals' are not designed to be air-tight. In fact, behind the seal there should be a tiny air-bleed hole through the carb body. I believe they are actually there to exclude grit/dirt from penetrating the bleed hole and getting into the carb throat. Happy to be corrected, though.

Maz
Ironically, Common Sense is the LEAST common of all senses!

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badandy
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Re: Not returning to idle.

Post by badandy » Thu May 04, 2017 8:01 am

Yes. I read that researching the common problems of "not returning to Idle". I am afraid that the actual bore in the carb body is worn excessively. If that is true then installing new felts aren't going to solve the problem. Worth a try with the money I have invested so far. I don't think there are any "replaceable" bushings in the carb body itself. The only correct fix then would be to find another set of carbs :(

mr green
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Re: Not returning to idle.

Post by mr green » Sat Jul 22, 2017 8:49 am

Hi badandy
I have been reading your posts and have the exact same problem, after extensive rebuild cleaning sync etc the 2,4 bank throttle pivots can be moved to alter the idle.Did you have to replace your carbs to fix the problem? Please let me know what Thanks

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badandy
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1983 VT500 Shadow

Re: Not returning to idle.

Post by badandy » Sat Jul 22, 2017 9:16 am

I replaced the ignition system with a Dyna unit and fresh coils so that variable is out of the picture. I replaced the throttle shaft felt seals (they really are not seals) and the problem is still there. I am riding the bike now, but it makes for hard shifts when the rpms are over 1500 when letting off the throttle to shift.

I was thinking of sealing off the air hole behind the "seals" and see if that makes a difference. Another thought is putting a rubber o-ring in place of the felt seal. I am concerned about binding when the seals get dry though.

I also have been eyeing up the Solex conversion deal. Seems like a lot less to deal with. This is a daily driver so high rpm operation is not a concern. I'm getting frustrated pulling these carbs repeatedly and having no solution.

On a side note. Starting this bike when cold is not cooperative. Constant fiddling with the choke and erratic rpm fluctuations are driving me nuts!

mr green
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Re: Not returning to idle.

Post by mr green » Sat Jul 22, 2017 10:29 am

Hi Andy
Thanks for the reply .I have Dyna and coils as well.I replaced the felts as well.I find it hard to imagine that the throttle shaft looseness would be the problem. On the bench the shaft seems to be tight and smooth etc.I can't see it being air infiltration problem either.It is almost like the throttle connection arm is a tad to long or short and puts pressure on the throttle shaft .Thje next thing I will try is to adjust the throttle cable to maybe affect change in the end pressure of the connecting rod. Blake

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badandy
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1983 VT500 Shadow

Re: Not returning to idle.

Post by badandy » Sat Jul 22, 2017 11:09 am

My throttle shafts felt good to me when I had them apart as well. Nothing odd. I have several carbureted bikes and just can't get a crisp return to idle on this one. I even changed the advance springs I the distributor with a known good set and that made no difference. Nature of the beast maybe?

I'll tear back into it this winter and try what I posted earlier. Maybe seal the holes in the carb bores AND add o-rings to the shafts. Something has to fix this. I'm pretty anal about things not working like they should and don't usually quit until I figure it out. I wish I had another bike to compare with.

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ekvh
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Re: Not returning to idle.

Post by ekvh » Sun Jul 23, 2017 10:34 am

A long shot, but look at your synchronize "pads" ( the pads the sync screws move against.) Check that washers are in the right place. Then look if they are bent or not. It is easy in dismantling to bend them. You don't say which bike but 1000's may need to be tweaked a bit to allow the throttle plates to close all the way. One out of tolerance can hold the others up as they are synced to each other. When the carbs are held open, push on the 1-3 sync and see if it drops down. If you find one, they can be easily pushed back into position.

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Re: Not returning to idle.

Post by mr green » Sun Jul 23, 2017 1:30 pm

Thank you very much.I am very open to any suggestion Blake

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aussiegold
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Re: Not returning to idle.

Post by aussiegold » Mon Jul 24, 2017 12:26 am

have a read of this thread and in particular post 41
https://www.ngwclub.com/forum/viewtopic ... e&start=30
but if you decide to dig in to your carbs again to replace the felts ( and no carb rebuild is COMPLETE without them )
have a look at this video, one of the best carb rebuild tips out there. he also supplies the felts ( or used to )




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badandy
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Re: Not returning to idle.

Post by badandy » Mon Jul 24, 2017 5:00 am

That is where I got mine.

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Re: Not returning to idle.

Post by mr green » Mon Jul 24, 2017 9:31 am

HI Thanks for the reply I have changed the felts as well and no difference.A I found out they are only to keep dust out and nothing to do with air as there is a hole under them to let air pass.
I don't believe my problem is an air problem because when the bike is running at 2000 rpm and I push down on the #2&4 sync adjustors they move down very slightly and rotate the shaft. This in turn changes the butterflies ( and covers more of the 3 holes under the butterfly,which indirrectly makes it an air situation,but the real problem is that the shaft moves and I haven't found out why yet .
When I get a chance (to busy to work on it now) I will disconnect the linkage rod and check shaft again.When I bench tested the carbs I could not feel any mushiness in the shaft.

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Re: Not returning to idle.

Post by biker art » Thu Jan 11, 2018 10:04 pm

Since you haven't posted anything for awhile I think you have the problem solved. Do wish you would let us know how things are going. As to the carb conversion I did it and had bad luck. The bike a GL1000 1975 would start every time but after many many tries I finally gave up. I could not get to fun on the street no matter how many times I tried different jets. It would idle but not perform. Kept stalling an had bad flat spot when I gave it throttle. Another $100+ wasted. I'm having return to idle issue now with rebuilt stock carbs but very strong response under higher acceleration.



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