78 Carb Questions


Information and questions on GL1000 Goldwings (1975-1979)
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whiteclad57
Posts: 27
Joined: Wed Apr 29, 2020 1:48 am
Location: Sisters, Oregon
Motorcycle: 1978 GL1000 Goldwing
1981 GL500 Silverwing

78 Carb Questions

Post by whiteclad57 »



I've been working on this bike the last 3 years and one of the last things I need to iron out is a rich running condition and an overheating issue that I can't seem to get rid of. I'm pretty sure the previous owner of the bike rebuilt the carbs with a barracuda or napco carb kit as none of the brass fittings or float needles are stock or even marked for that matter. I've since used a randakk kit to replace all the gaskets and o-rings but the bike still has a persistent rich running condition on all four cylinders with the left rear cylinder being more prominent than the others.
I just want to confirm before I start buying OEM carb parts at significant markup, that what I have is out of spec, does anyone happen to know the correct length end to end for the jet needle on the late 78 (771A) carb body?
I'll probably be replacing the fuel and air jets regardless just to make sure what I have is correctly sized. And of course, I'll be setting the ignition timing from scratch as well to ensure that retarded timing isn't the biggest source of these issues.


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Rambozo
Posts: 3625
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Location: Disneyland
Motorcycle: 1992 GL1500 Aspencade
Ducati Monster

Re: 78 Carb Questions

Post by Rambozo »

The length of the needle isn't so much the issue as the taper. Going back to OEM is a great idea. Plenty of horror stories about some of the cheaper kits. Unless the carbs have been at the bottom of the ocean, there is almost never anything wrong with the jets or needles that a good cleaning wouldn't fix. But if it's in the kit people feel like they have to use them.
I guess you could buy jets and a needle for one carb, then measure with pin gauges to compare to what you have. Do you have 31mm or 32mm bore carbs?
whiteclad57
Posts: 27
Joined: Wed Apr 29, 2020 1:48 am
Location: Sisters, Oregon
Motorcycle: 1978 GL1000 Goldwing
1981 GL500 Silverwing

Re: 78 Carb Questions

Post by whiteclad57 »

What's on the bike is the emission controlled 78 carbs (32mm), I bought a second set of pre-emissions 78 carbs that I had hoped to swap on unfortunately it appears the jet tower emulsions are completely destroyed and crumbling, it does have all OEM parts though so maybe I will just swap them all out with maybe the exception of the idle air jet which they changed from #120 to #130 in the later model, although I'm not sure if that was the only change in that carb series so maybe it's fine to swap that as well. It's unfortunate that everyone who's worked on this bike was sure they knew what they were doing and just didn't at all. Hell just today I noticed that some of the screws on the points plate are head stripped, missing washers and one has even been possibly interfering with the spark advancer this whole time given the tolerance between the mounting plate and its location, which is ironic because the last person who messed with the ignition on the bike is well known in the city for being the only business licensed mechanic to work on Goldwings.
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cfairweather
Posts: 130
Joined: Mon Jul 10, 2017 2:00 pm
Location: Cheyenne, WY
Motorcycle: Two restored 1975 GL1000, 2013 BMW R1200RT, two restored 1971 K1 CB750s, 2014 Valkyrie
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Re: 78 Carb Questions

Post by cfairweather »

As long as you measure third party air/fuel jets with a gauge to ensure the hole is the correct size, you are ok but I prefer using the originals. Use the original Honda needle jets and the number on them should be 452304. The original idle screw jets should always be used. If a third party one was ever installed and screwed in tight, the tiny hole where the tip seats might be enlarged. The third party tips are often slightly larger than the original and should never be used. Use the original float valve needles and seats. If don't want to spend the money on getting new expensive Honda replacements, get the Keyster brand. These are high quality, maybe better than the originals and they have two choices, but both models have Viton tips. I also like the Keyster layered float bowl gaskets.

Get rid of the points and go to the Dyna style electronic ignition. You can get these on eBay for about $45.00. Also get new Dyna style coils for about 45.00 on eBay. I have written instructions and they are on this web site and NGW Club web site to help you.

Hope this helps.
Cedric

https://www.siriusconinc.com/products/detail/125326
https://www.siriusconinc.com/products/detail/527
https://www.randakksblog.com/error-in-o ... /#more-255
Emile
Posts: 24
Joined: Fri Nov 12, 2021 10:08 am
Location: France
Motorcycle: GL1000 1979

Re: 78 Carb Questions

Post by Emile »

Hello,

I have troubles with my '79 GL1000.

I think i have the original needle jet emulsion configuration.
For the emulsion tube it is a 2 pieces : 1 brass tube wit 5+2 holes, and one stainless hat.
Regarding the needle iI have 2 version one stainless and one brass. The stainless seems to be the correct one with #452304 on it.

Bike is running great at idle and full throttle.
But when I start opening the throttle, it is like nothing happes for few seconds, it feels like the mixture is not correct for mid opened throttle.
Usually it is a problem of needle height, but for this bike it is not possible to set it.

Does someone have an idea what can be my issue ?
Thanks
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cfairweather
Posts: 130
Joined: Mon Jul 10, 2017 2:00 pm
Location: Cheyenne, WY
Motorcycle: Two restored 1975 GL1000, 2013 BMW R1200RT, two restored 1971 K1 CB750s, 2014 Valkyrie
Contact:

Re: 78 Carb Questions

Post by cfairweather »

Here is a link to verify your needles are correct:
https://www.randakksblog.com/error-in-o ... /#more-255

Here is a link to see the emulsion tube variations.
https://www.randakksblog.com/emulsion-tube-variations/

The slides might not be operating correctly due to button leaks or they might be sticking. They must operate perfectly without any friction. They must be polished and this includes all surfaces: The outside of the slides, the cap cavity, the rod guide hole, the shaft itself and even the carburetor shaft hole. All of these components must be absolutely clean or the slide will bind. Another possibility: The emulsion tube holes might be plugged.
Emile
Posts: 24
Joined: Fri Nov 12, 2021 10:08 am
Location: France
Motorcycle: GL1000 1979

Re: 78 Carb Questions

Post by Emile »

Hi,

M float level was at 23mm... No idea how that was possible to make this mistake.
But it seems to have solve my issue.

I also checked the correct operation of the slides. Nothing strange but still I clean all slides.

So having a level at 23mm I think it means low fuel pressure and a lean mixture at small throttle opening.

Thanks for the help


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