VW carb switch, 34 to 30

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ob1quixote
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VW carb switch, 34 to 30

#1

Post by ob1quixote »

Went from the Solex 34 to the Solex 30.
Seems I was always fighting the idle, and never got the performance and fuel mileage I wanted.

Always felt the 34 had too large a bore for the 1000cc motor, and that the 30 with its smaller bore would provide a better fuel charge at idle.

Removed the solenoid and plugged the port, transferred the manual choke and mounted it up. Wasnt crazy about the 34 to 30 plate adapter, seems like the studs were splayed out, so I had to ream out the mounting holes on the manifold. Even with the adapter plate and the 1/4in phenolic spacer, the tool tray still fits in the faux tank.

Was rewarded with a reasonable idle at first start! No road test due to weather and other work to finish up on the bike, but looking forward to some minor tweaking and testing.
1979 GL1000
2001 DRZ400
1983 CR480
And a few late '60's - early '70's British thumpers
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Sugs
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Re: VW carb switch, 34 to 30

#2

Post by Sugs »

I've not ever done a conversion myself, but after reading a ton of info on the subject I've had the same thought that the 34 is just too big and the 30 would be a better starting point. Will be interested to see how it goes for you.
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'79 Honda GL1000 Goldwing
ob1quixote
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Re: VW carb switch, 34 to 30

#3

Post by ob1quixote »

I put a few thousand miles on it with the 34,and while it is workable, I think there may be a better conversion carb. Hope the 30 is it!
1979 GL1000
2001 DRZ400
1983 CR480
And a few late '60's - early '70's British thumpers
ob1quixote
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Re: VW carb switch, 34 to 30

#4

Post by ob1quixote »

Changed the main jet from 120 to 142.
Changed the air correction jet from 120 to 65
Changed power jet from 80 to 50.

Very happy so far, will need minor tweaking if the idle air screws, then a mileage test!
1979 GL1000
2001 DRZ400
1983 CR480
And a few late '60's - early '70's British thumpers
ob1quixote
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Re: VW carb switch, 34 to 30

#5

Post by ob1quixote »

All it took was a few minutes to tweak idle screws to get a very stable idle! Next up, mileage tests.

Even if the mileage doesn't increase, this 30 carb is superior to the 34 hands down.
1979 GL1000
2001 DRZ400
1983 CR480
And a few late '60's - early '70's British thumpers
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Sugs
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Re: VW carb switch, 34 to 30

#6

Post by Sugs »

Great to hear. Will be interested to see how well it runs on the highway, especially in passing situations when you wack the throttle open.
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ob1quixote
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Re: VW carb switch, 34 to 30

#7

Post by ob1quixote »

My first ride was very good, with the only issue a slight flat spot in the higher rpm. She will boogie!

Gonna have a look at my stock of air correction jets, and go up on it.
1979 GL1000
2001 DRZ400
1983 CR480
And a few late '60's - early '70's British thumpers
ob1quixote
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Re: VW carb switch, 34 to 30

#8

Post by ob1quixote »

Bumped the air correction jet to a 70. Waiting for the rain to go away for some test miles!
1979 GL1000
2001 DRZ400
1983 CR480
And a few late '60's - early '70's British thumpers
ob1quixote
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Re: VW carb switch, 34 to 30

#9

Post by ob1quixote »

First mileage test done, mostly state roads, cruising at 4Krpm for the most part.

26mpg, not great

Have to look at the main and power jets, then readjust the air correction jet. The idle is wonderful when warm, so not planning any changes there, and the little flat spot at WOT is all but gone
1979 GL1000
2001 DRZ400
1983 CR480
And a few late '60's - early '70's British thumpers
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taunusrainer
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Re: VW carb switch, 34 to 30

#10

Post by taunusrainer »

A guy named Ron Winkler did this 20 years ago, he, too, recommended not to use the 34 but the 30 PICT.
I remember he was jetting a lot and finally got acceptable idle at 1100rpm. But the bike became a luster performer at high rpm. The 30 PICT was designed for 30hp engines. No way can it supply enough flow for the goldwing engine. All single carb converters finally ended up with a progressive 2bbl Weber or Nikki. I remember the best results were with CC products coolant heated manifold and Weber 28/36 DCD.
ob1quixote
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Re: VW carb switch, 34 to 30

#11

Post by ob1quixote »

As it is set up now after a few unnoted jet changes, I have a wonderful idle, and a very nice "boogey" mode to red line!

Working on beefing up a small stumble between 1500 and 2500rpm, and looking for better fuel economy. Jets on order from Italy.

Another unnoted change, I went from a fully insulated manifold to make use of the heat in the crossover tube to only covering 1/2 of the manifold, centered at the carb. Manifold being cooled by the fuel air mixture is real, I have an electronic thermometer/thermostat that proves it. What isnt proven is how effective the grip heaters on the manifold are, switched by that thermostat.

I could leave it as it sits and be fairly happy with the set-up, just chasing a finer tune!
1979 GL1000
2001 DRZ400
1983 CR480
And a few late '60's - early '70's British thumpers
hep2
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Re: VW carb switch, 34 to 30

#12

Post by hep2 »

I am getting ready to make the switch to a single carb and I see the best performance as tested by many people is a 2 barrel 32/36 weber but that required a lot of fiddling around and then I got to looking at theese VW carbs and I read a lot about ice, heating and cooling problems and I noticed one big difference between those that reported problems and those that did not was that the ice and cold manifold temps only seem to occure in the manifolds that did not have anactual plenum between the carb and the runners. some manifolds just have runners to a flange mount and there you go. do you suppose this has any merit or do I just need to do more reasearch?
Rick
1980 GL1100
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ericheath
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Re: VW carb switch, 34 to 30

#13

Post by ericheath »

A little somewhat factual food for thought:
0423A145-9D0D-4F2A-B0E5-3D1F8D7EFA2A.jpeg
0423A145-9D0D-4F2A-B0E5-3D1F8D7EFA2A.jpeg (133.91 KiB) Viewed 1271 times
From a Hitachi shop manual.
Whatever I suggest here should be given ample time for a moderator to delicately correct. I apologize in advance.
77 WING, 1200 engine with 77 heads, cams, gl1100 foot pegs, Magna V65 front end, 764A carbs, [-gone Suzuki M109 monoshock--, replaced with gl1100 shocks] gl 1200 swing arm, gl1500 final drive, wheel and rear brakes Valkyrie seat, Meanstreak tank, Sportster pipes, Power Arc ignition off crank.
77 Wing. black
83 Wing, in pieces
"Continuing education is important even if the subject matter is fairly useless (as in this case)."---Greg Foresi
hep2
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Re: VW carb switch, 34 to 30

#14

Post by hep2 »

So then are you saying that manifold design has nothing to do with icing?
Rick
1980 GL1100
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robin1731
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Re: VW carb switch, 34 to 30

#15

Post by robin1731 »

hep2 wrote:So then are you saying that manifold design has nothing to do with icing?
Perhaps not "nothing". But other factors come in to play too. Some people think carb icing only occurs when temps are pretty cold. That chart shows what can happen even well above freezing.

.
1976 Goldwing Super Sport
1985 Honda Elite
1976 KZ900 Dragbike
1992 ZX7 Dragbike (KZ900 style motor w/NOS)
and a rotation of various purchases
Randakk approved Carb Rebuilder
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