I know, I know, this has probably talked about before. Sorry

This is where discussions of EFI systems, Dual Carbs, Single Carb mods and plans can be discussed and shared.

If you are working on or have a problem with stock carbs then your questions do not belong here, please post them in the Goldwing Tech Discussions Forum.

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CYBORG
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Re: I know, I know, this has probably talked about before. S

#31

Post by CYBORG »

I've heard that before. The stock set up is just four single carbs. One for each cyl. So how is one single better?
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Re: I know, I know, this has probably talked about before. S

#32

Post by TheWheel »

CYBORG wrote:I've heard that before. The stock set up is just four single carbs. One for each cyl. So how is one single better?
I guess it depends how you measure "better".

Logic says that single would be simpler, only one to maintain and takes care of balancing automatically.

From reading here and elsewhere its not that simple though. Getting a single carb, not designed for this application, set up right to work on a 4 cylinder bike that revs relatively high (vs the designed application eg VW beetle) using a amateur designed manifold/plenum that might ice up is not without its own complexities.

The thing that made me consider this option was desperation.

If you are lucky and have a good set of standard carbs that balance nicely then I can see why you would find it hard to see why someone might consider the single carb route.
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Re: I know, I know, this has probably talked about before. S

#33

Post by CYBORG »

Some years ago I decided to bite the bullet, and try and understand the goldwing carbs. After I got over that hurdle the carbs became much easier to understand and to work on. Since then I don't see them as a mystery. And I find that a good set of stock carbs work very well, and as intended
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Re: I know, I know, this has probably talked about before. S

#34

Post by Scooter »

I spent 2 months of experimenting and jetting a new 34PICT-3 VW carb and a steel plenum manifold and was not satisfied. I was frustrated with the stock carbs and was looking for easy. I did find some big improvements through jetting, accelerator pump adjustments and timing changes, but never got it right. The 2 big issues were: no pulling power below 3000 rpm and it ran out of steam at 6000 rpm. I checked plug color and it was not even from cylinder to cylinder. I have since returned to the stock carbs and really appreciate them now. I can let out the clutch and it will pull smoothly from a stop at 1500 rpm and will continue pulling to redline and I'm averaging 40+ mpg. It was a learning experience and I don't consider it wasted time. Good luck to those that try it, but I would like proof of a single set up that performs as well overall as the original. I just wasn't willing to compromise that much. Anyone interested in a slightly used single carb setup?
1976 GL1000 LTD for sale
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Re: I know, I know, this has probably talked about before. S

#35

Post by TheWheel »

Scooter wrote:Anyone interested in a slightly used single carb setup?
I'll swap you for my old weak springed gas tank cap. :-D
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Re: I know, I know, this has probably talked about before. S

#36

Post by brianinpa »

Scooter wrote:I spent 2 months of experimenting and jetting a new 34PICT-3 VW carb and a steel plenum manifold and was not satisfied. I was frustrated with the stock carbs and was looking for easy. I did find some big improvements through jetting, accelerator pump adjustments and timing changes, but never got it right. The 2 big issues were: no pulling power below 3000 rpm and it ran out of steam at 6000 rpm. I checked plug color and it was not even from cylinder to cylinder. I have since returned to the stock carbs and really appreciate them now. I can let out the clutch and it will pull smoothly from a stop at 1500 rpm and will continue pulling to redline and I'm averaging 40+ mpg. It was a learning experience and I don't consider it wasted time. Good luck to those that try it, but I would like proof of a single set up that performs as well overall as the original. I just wasn't willing to compromise that much. Anyone interested in a slightly used single carb setup?
What were the jet sizes that you were using (idle and main)?
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Re: I know, I know, this has probably talked about before. S

#37

Post by Scooter »

#60 idle and #122.5 main was the final combo. I had tried #50, 55, 60 and 65 idles and #117.5, 120, 122.5 mains in various combinations. The carb came with #65 idle and #130 main. Here's the link to some very good jetting information as it applies to aircooled VWs. I also reduced my runner diameter to 1" and it really helped with the idle. http://www.vw-resource.com/jets.html
1976 GL1000 LTD for sale
1982 CX500C customized
1976 GL1000 Sulphur Yellow project
1978 GL1000 Blue rat project
1978 GL1000 Black project/parts
1978 GL1000 parts, not many left
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1982 GL500 Interstate
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Re: I know, I know, this has probably talked about before. S

#38

Post by brianinpa »

Thanks! I've been reading everything I can find at vw-resource.
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Re: I know, I know, this has probably talked about before. S

#39

Post by socrace »

Probably the main issue with using an air cooled vw carb on a goldwing is that the vw 1600 motor idles at 15-17 inches of vac, where the goldwing has about 8-9 inches max. The vw idle fuel circuit is just way too small to feed the low vac goldwing.
A better single carb choice might be one from a slow turning, big inch engine, one with a max horsepower output similar to the goldwing. The single barrel carb used on an early 60's 300 cid (5 litre) Ford straight 6 truck engine might work pretty well. It's rated about 100 hp at 3400 rpm (on a good day) and has idle circuits big enough to feed 5 litres at idle. From memory, it actually doesn't look much bigger than a VW single barrel.
No guarantees, of course! Just my random thoughts...
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Re: I know, I know, this has probably talked about before. S

#40

Post by TheWheel »

socrace wrote:the vw 1600 motor idles at 15-17 inches of vac, where the goldwing has about 8-9 inches max. The vw idle fuel circuit is just way too small to feed the low vac goldwing.
It seems to me that this is really good information to start a proper search for a better candidate carb. It seems to me that the reason VW Beetle carbs have been used is because there is a logic in using a carb from a 4 cylinder boxer engine on a boxer engine and a plenum/intake from a 4 cylinder Boxer engine. But really that is the wrong starting point and as a result the trial and error has been going in the wrong direction. Possibly!
Last edited by TheWheel on Wed Oct 21, 2015 7:01 am, edited 1 time in total.
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Re: I know, I know, this has probably talked about before. S

#41

Post by 82aspy »

idle circuits too small would mean running lean, no? the reports are rich conditions with plugs loading up at idle/low RPMs with the dft
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Re: I know, I know, this has probably talked about before. S

#42

Post by ericheath »

To the argument that the runners are long, icing issues, or whether it's viable at all, etc. The 1500 uses two singles, one feeding each side. They're known to be very smooth everywhere. Not sure if they all do, but the 15's I've seen do use heat from the exhaust manifolds. It must be able to be done with a four cylinder. Getting the right carb, the right manifold, and dialed in is the trick.
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Re: I know, I know, this has probably talked about before. S

#43

Post by socrace »

Some carbs meter too much fuel at low vac idle. I think mostly the newer ones with "air adjust" mixture screws.
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Re: I know, I know, this has probably talked about before. S

#44

Post by 82aspy »

socrace wrote:Probably the main issue with using an air cooled vw carb on a goldwing is that the vw 1600 motor idles at 15-17 inches of vac, where the goldwing has about 8-9 inches max. The vw idle fuel circuit is just way too small to feed the low vac goldwing.
A better single carb choice might be one from a slow turning, big inch engine, one with a max horsepower output similar to the goldwing. The single barrel carb used on an early 60's 300 cid (5 litre) Ford straight 6 truck engine might work pretty well. It's rated about 100 hp at 3400 rpm (on a good day) and has idle circuits big enough to feed 5 litres at idle. From memory, it actually doesn't look much bigger than a VW single barrel.
No guarantees, of course! Just my random thoughts...
problem right away is sourcing a cheap carb with knowns, no way any carb is viable to others interested in gw scc without cost and givens being known to begin with, and cheap,

way cheaper is prob the biggest selling point/draw for scc, along with easier, which are the hooks,

dunno what the main issue is as far as carb selection goes, a few folks at least claim a bug carb variant is bolt on good to go and show compelling supporting evidence, my wag is not having sourced a known carb so folks end up with results all over the place,

same deal with the known langdon 32dft that in the last few years, has been THE focus & go to gw scc, it was initially and for years afterwards (even still today) promoted as bolt on good to go that turned into mixed results at best for others, not to mention far from bolt on to begin with, along with rich running st low RPMs issues fouling plugs etc..

gw scc was and remains mostly a black art with many big claims and few results in the bigger picture,

the bigger picture with results speaks for itself, whereas scc promoters tend to trash it & that gets old quick

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Yoda said, "There is no try or not try; there is only do or don't do."
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Re: I know, I know, this has probably talked about before. S

#45

Post by Captain Midnight »

gregforesi wrote:CaptainMidnight used the EMPI VW manifold (shown previously) and added a coolant line to the underside to combat the icing issue.
If I might clarify,..
..no, not added to combat any carburetor icing issue. I introduce heated intake air for that, which can be a very real problem; icing.
So, no, it's not done for that reason at all.

I heat the plenum and runners to (1) centralize the fuel charge within the delivery tract and (2) maintain full suspension of what is atomized from the carburetor.

Hope this clears up why I apply heat.

CM
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