Carb staying on high RPM after accelerating.

[Bub II]

I’ve got a problem with my air cooled VW sandrail carb.
Whenever I punch the throttle, it accelerates normally, but when I let off, it’s like it’s on fast idle and I have to blip the throttle to get it back to normal idle.
I had an old time VW mechanic work on it a few years ago, and I remember him saying he swapped out the carb for a rebuilt one. I think it started doing this after the carb swap. I haven’t gotten to drive it much since due to other projects and wiring issues and I just recently occurred to me that the original carb may have been modded for off-road use?
It appears that possibly the fast idle cam is dropping into play when the throttle is punched, and that keeps the RPMs up when my foot is removed from the throttle.
Do most people remove the choke/fast idle cam on these carbs for off-road use?
I redid the throttle cable because I thought it might be the issue, but that didn’t help.
Thanks in advance!
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Enjoying life one day at a time.

[Dale M.]

Got good return spring...

Dale
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“Fear The Government That Wants To Take Your Guns" - Thomas Jefferson.

"Kellison Sand Piper Roadster" For Street & Show.
"Joe Pody Sandrover" Buggy with 2180 for Autocross (Sold)
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All suggestions and advice are purely my own opinion. You are free to ignore them if you wish ...

[Bub II]

Thanks for the reply.
The carb throttle has double springs to ensure the throttle cable is returning fully.
I’ve been thinking of drilling a small hole in the fast idle/choke cam and putting a spring on it to keep it from dropping into the fast idle position.
Maybe the choke control isn’t working correctly.
I also thought maybe it was common to remove the cam all together to avoid this issue?
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Enjoying life one day at a time.

[andk5591]

So punch it and go back and look to see whats causing it to hang up. If its the fast idle cam you should be able to adjust the choke to keep it open more. Its also VERY possible that your ignition advance is hanging up. Will cause the sam kind of problem if it eventually comes back down on its own. Most folks forget that there is a little felt tab under the rotor that is supposed to get a couple drops of oil on it periodically. If you are running in sand or dirt, you just might have crap on the advance as well - seal up the distributor.....
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[Dark Earth]

My carburetor was sticking and I found the throttle arm was hitting the manifold.

I bent the arm straight and shaved off the barrel nut a bit. Now it's a lot smoother.

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My Build: '69 Baja - Dark Earth Version

~I'm almost done. I just lack finishing up.~

[Bub II]

Thanks for all the replies and pictures so far.
I’ll check out my carb and see if I can rule out each solution or if you’ve identified my problem.
Rob at Rob and Dave’s suggested I check to see if my choke was properly connected or if possibly it was floating Free, allowing the choke cam to swing under the idle screw, causing the fast idle after accelerating.
The people here are a wonderful resource and very helpful to fellow VW enthusiasts.
Thanks!!
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Enjoying life one day at a time.

[Bub II]

First pic should be how I found the carb choke cam today.
Second pic is the corrected position.... I hope.

Evidently, Somehow the cam got rotated 180 degrees and that was causing issues. There is probably an issue with the choke/linkage too.

I need to get a good battery and get it started again to see if this solves the original problem.

Opinions? Is it worth repairing the choke on a sandrail or just remove altogether?
Thanks!
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Enjoying life one day at a time.

[Q-Dog]

There is supposed to be a pin in the carb body that goes through that slot in the cam to keep it from rotating that far.

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Brian

'69 Dune Buggy
'69 Beetle Convertible
'70 Beetle

[Bub II]

Ok, that makes sense!
The picture really helps me. I see where the Roll pin should be.
Thanks Q-Dog!
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Enjoying life one day at a time.

[Fenix]

[dustymojave]

2 return springs are a GOOD thing. In case one breaks, there is another to prevent stuck throttle syndrome. 2 is required for offroad race cars.

However... The 2 springs need to NOT interfere with each other.
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Richard
Offroading VW based cars since 1965
Tech Inspection 1963 - 2012 SCCA/SCORE/HDRA/MORE/MDR +
Retired from building Bajas, Fiberglass Buggies and Rails in the Mojave Desert. Also Sprints & Midgets, Dry Lakes, Road Race cars. All types New and Vintage
SoCalBajas Member
Kicked Cancer's A$$...1st and 2nd round...Fight ain't over yet.

[pullstart]

I've seen a smaller diameter spring inside a larger diameter... would this pass? I think it's common on circle track, not saying they are always right.
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4 seater Appletree buggy, road legal with 002 IRS, 3x3 Appletree kit, 6" over Dan's beam with 10" towers and Fox 2.0 shocks, '00 Subaru EJ25 with KEP stage 3 clutch and KEP adapter plate.

my build page: https://www.thesamba.com/vw/forum/viewtopic.php?t=662104&start=0

[Dale M.]

[pullstart]

I'm using the stock return spring on the throttle body of my EJ25 and it works great, I was simply asking if the spring in a spring setup would be accepted in Dusty's tech check.
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4 seater Appletree buggy, road legal with 002 IRS, 3x3 Appletree kit, 6" over Dan's beam with 10" towers and Fox 2.0 shocks, '00 Subaru EJ25 with KEP stage 3 clutch and KEP adapter plate.

my build page: https://www.thesamba.com/vw/forum/viewtopic.php?t=662104&start=0

[Dale M.]

[pullstart]

Here's a post in another forum (google search) that shows what I'm talking about: http://www.camaros.net/forums/18-engine/169906-dual-throttle-return-spring.html
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4 seater Appletree buggy, road legal with 002 IRS, 3x3 Appletree kit, 6" over Dan's beam with 10" towers and Fox 2.0 shocks, '00 Subaru EJ25 with KEP stage 3 clutch and KEP adapter plate.

my build page: https://www.thesamba.com/vw/forum/viewtopic.php?t=662104&start=0

[Fenix]

[Bub II]

In my case, I doubled the spring trying to stop my issue with the carb not returning to normal after acceleration. It doesn’t appear to be intermingling or binding, but now that I’ve fixed the real problem, I’ll be removing one of them.
Turns out, the Roll pin that goes through the slot in the fast idle cam on my carb is either broken or missing allowing the cam to rotate 180 degrees and blocking the throttle from returning to normal idle.
I swapped batteries today and started the engine. At this point I figured out my choke element is evidently bad also.
Anyway, I let it warm up until it would idle, then blipped the throttle several times and each time it returned to normal idle as it should.
Now I need to decide whether to replace the carb or just the choke element and try to get the broken roll pin out of the carb body?
Thanks to every one who gave ideas and suggestions.
Something so simple as a missing Roll pin and a bad choke element caused a lot of grief.
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Enjoying life one day at a time.

[Krochus]

I have discovered that between my rail and my Baja that a little bit of cable slack is required or what you observe is going to be the result.

I know the tendency is to adjust the throttle cable to zero slack. But I’ve had terrible luck in doing so

[Dale M.]