Accelerator circuit massage
Moderator: Whiskerfish
- mikenixon
- Early 'Wing Guru
- Posts: 997
- Joined: Thu Dec 10, 2009 1:51 am
- Location: Prescott, AZ
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Accelerator circuit massage
On the GL1100, Honda did something very needful. They added an accelerator pump to the carburetors. Together with smaller throats, these two changes made a huge improvement over the GL1000's carb set, tuning the GL1100's carbs much closer to the way the motorcycle was actually being ridden.
The GL1100's carburetors are of a family Keihin called "VB", a designation which you can see cast into the side of each carburetor body, and a family of carbs Honda used on most of their bikes during the early 1980s. And excepting some Euro and other variations, all of the VB series carbs used during this time have accelerator pump circuits. This includes the six-cylinder CBX, the DOHC inline fours, the 650 four, the 500 and 650 and 400 twins, and even the FT500 single. All have this same accelerator pump system.
It's a good system, the accelerator pump, but it has a fault. Its discharge orifice is so tiny it clogs easily. Coupled with a very low pressure operating diaphragm, it's a cinch most GL1100s are not benefitting from all the throttle response they should be due to a weak accelerator pump system.
Here's how I fix that. I usually try heat first. More than half the time however it isn't enough. I have a piece of a guitar string clamped in a pin vise, which is just a handle to hold very small drills. The pin vise is extended with a piece of welding rod for better reach. After opening both the throttle and choke plates, or sometimes even removing them, I shoot a flashlight down the carb throat and at the same time ease this special tool down to the accelerator pump's upright nozzle. Once in the nozzle's discharge orifice, I rotate the tool to auger the nozzle, which dislodges any varnish or rust (usually both). I'll remove the tool and test the nozzle with an brake cleaner aerosol, and if needed, repeat with the tool. After trying hydraulic methods, heat, and more, this technique has become the one I always use, when needed, on all of the carburetors I rebuild.
Mike Nixon
www.motorcycleproject.com
https://www.motorcycleproject.com/text/ ... _carb.html
https://youtu.be/CDnzwDWhN24
https://www.motorcycleproject.com/text/lies_ether.html
www.motorcycleproject.com
https://www.motorcycleproject.com/text/ ... _carb.html
https://youtu.be/CDnzwDWhN24
https://www.motorcycleproject.com/text/lies_ether.html
- Track T 2411
- Honored Life Member
- Posts: 8482
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- Location: Prairie du Sac Wisconsin
Re: Accelerator circuit massage
Good to know that I wasn't doing a 'bad' thing when I used a wire brush bristle clamped into a small hemostat when I found one plugged on my last build, lol!
- mikenixon
- Early 'Wing Guru
- Posts: 997
- Joined: Thu Dec 10, 2009 1:51 am
- Location: Prescott, AZ
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Re: Accelerator circuit massage
Good man! The accelerator pump is pretty important, isn't it?
Mike Nixon
www.motorcycleproject.com
https://www.motorcycleproject.com/text/ ... _carb.html
https://youtu.be/CDnzwDWhN24
https://www.motorcycleproject.com/text/lies_ether.html
www.motorcycleproject.com
https://www.motorcycleproject.com/text/ ... _carb.html
https://youtu.be/CDnzwDWhN24
https://www.motorcycleproject.com/text/lies_ether.html
- Track T 2411
- Honored Life Member
- Posts: 8482
- Joined: Thu May 29, 2008 9:37 pm
- My Album: http://www.ngwclub.com/gallery/v/wingmans/Track+T+2411/
- Location: Prairie du Sac Wisconsin
Re: Accelerator circuit massage
Certainly makes a difference compared to the off idle issues of my '76...
- mikenixon
- Early 'Wing Guru
- Posts: 997
- Joined: Thu Dec 10, 2009 1:51 am
- Location: Prescott, AZ
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Re: Accelerator circuit massage
I have a video for you to look at...Track T 2411 wrote:Certainly makes a difference compared to the off idle issues of my '76...
https://youtu.be/CDnzwDWhN24
Mike Nixon
www.motorcycleproject.com
https://www.motorcycleproject.com/text/ ... _carb.html
https://youtu.be/CDnzwDWhN24
https://www.motorcycleproject.com/text/lies_ether.html
www.motorcycleproject.com
https://www.motorcycleproject.com/text/ ... _carb.html
https://youtu.be/CDnzwDWhN24
https://www.motorcycleproject.com/text/lies_ether.html
- Track T 2411
- Honored Life Member
- Posts: 8482
- Joined: Thu May 29, 2008 9:37 pm
- My Album: http://www.ngwclub.com/gallery/v/wingmans/Track+T+2411/
- Location: Prairie du Sac Wisconsin
Re: Accelerator circuit massage
Thanks for the video tease, lol! I was hoping for a comprehensive 'how- to. (I know, I'm needy, lol) My question is how do I get my '76 there?
- pidjones
- SUPER BIKER!!!!
- Posts: 3237
- Joined: Wed May 22, 2013 4:06 pm
- Location: East TN
Re: Accelerator circuit massage
A high "E" in a pin vise is exactly what I used for the accelerator jets in the '79 CB750F that I rescued last year. That's a tiny hole, a long way off, though! The other tool needed is perseverance!
- mikenixon
- Early 'Wing Guru
- Posts: 997
- Joined: Thu Dec 10, 2009 1:51 am
- Location: Prescott, AZ
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Re: Accelerator circuit massage
Yes it does. But it is effective, and I do it a lot also.pidjones wrote:A high "E" in a pin vise is exactly what I used for the accelerator jets in the '79 CB750F that I rescued last year. That's a tiny hole, a long way off, though! The other tool needed is perseverance!
I know a fellow that removes accelerator pump system discharge nozzles in attempts to clean them, but I have considered that little too much. They can't be cleaned any differently out of the casting than in, and after removing one on a junk carb for practice, I don't like the method.
Mike Nixon
www.motorcycleproject.com
https://www.motorcycleproject.com/text/ ... _carb.html
https://youtu.be/CDnzwDWhN24
https://www.motorcycleproject.com/text/lies_ether.html
www.motorcycleproject.com
https://www.motorcycleproject.com/text/ ... _carb.html
https://youtu.be/CDnzwDWhN24
https://www.motorcycleproject.com/text/lies_ether.html
- mikenixon
- Early 'Wing Guru
- Posts: 997
- Joined: Thu Dec 10, 2009 1:51 am
- Location: Prescott, AZ
- Contact:
Re: Accelerator circuit massage
Lot of massaging. Ignition maintenance that goes beyond what most folks are willing to do, and carburetor massaging and tweaking that likewise could be described as epic. I have been doing both for as long as I can remember.Track T 2411 wrote:Thanks for the video tease, lol! I was hoping for a comprehensive 'how- to. (I know, I'm needy, lol) My question is how do I get my '76 there?
Mike Nixon
www.motorcycleproject.com
https://www.motorcycleproject.com/text/ ... _carb.html
https://youtu.be/CDnzwDWhN24
https://www.motorcycleproject.com/text/lies_ether.html
www.motorcycleproject.com
https://www.motorcycleproject.com/text/ ... _carb.html
https://youtu.be/CDnzwDWhN24
https://www.motorcycleproject.com/text/lies_ether.html
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