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Adjust My Carb Idle Speed
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TjdTaylor
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PostPosted: Sat Aug 13, 2011 3:40 pm    Post subject: Adjust My Carb Idle Speed Reply with quote

My idle speed is REDICULOUSLY high. I dont know the exact rpm's cause i dont have a tach. My engine was installed by the PO and im thinking my mighta effed something up. Its a 74 super and the engine is 1641cc. Ive turned this little screw thingy that contacts the electric choke. That made it abit better but not great. should i just get a profesional tune up or replace the carb (Either way im goina get a tune up if i cant get it fixed on my own)
Heres my engine

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What would posess somoebody to paint the engine this color? I have no idea
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Jamies74sb wrote:
I can't see myself cutting up my super beetle . Maybe a oval or 61 or so with the small windows
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rowjims
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PostPosted: Sat Aug 13, 2011 4:09 pm    Post subject: Reply with quote

furthermore, is there a 'redneck' way to determine RPMs without me having to go buy a tach/rpm meter from Harbor Freight.
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TjdTaylor
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PostPosted: Sat Aug 13, 2011 4:25 pm    Post subject: Reply with quote

rowjims wrote:
furthermore, is there a 'redneck' way to determine RPMs without me having to go buy a tach/rpm meter from Harbor Freight.


I dont need a way to determine rpm's, i know they are freiken high i can just tell, and ill be in second gear not even touching the gas going 30, pretty sure thats not natural. I need a way to get them down, I can get the rpms down with abit of carb adjusting but then it wont idle for $#!%.
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Jamies74sb wrote:
I can't see myself cutting up my super beetle . Maybe a oval or 61 or so with the small windows
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glutamodo Premium Member
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PostPosted: Sat Aug 13, 2011 4:53 pm    Post subject: Reply with quote

What about the timing, if that's been bumped (advanced) it can make it idle fast. Have you checked that?

Vacuum leaks will make it idle fast. Have you checked that?

If it happens you have a 1971-mid73 DVDA style German carb, and are running an SVDA distributor, you may find it hard to get the idle speed down due to the DVDA carb having a larger bypass hole in the throttle butterfly.

Have you tried to set the carb up properly? You have three things on the carb that influence idle. I'm guessing you backed off the throttle lever screw, where it contacts the fast idle cam of the choke. On 34PICT-3 carbs that is supposed to be ALL the way backed off, then screwed in until it only just slightly contacts the (choke open) fast idle cam. THEN you adjust your mixture and idle speed screws (volume and air bypass screws)


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jharte
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PostPosted: Sun Aug 14, 2011 7:21 am    Post subject: Reply with quote

X2. I also use these websites:

http://www.vw-resource.com/carb.html

http://www.vw-resource.com/34pict3.html

Jharte
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jdarends
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PostPosted: Sun Aug 14, 2011 7:30 am    Post subject: Reply with quote

My question goes back to the install. Did you check and make sure that the throttle cable is slack enough at idle that it does not partially hold the throttle open. If the cable is too tight all of the setting changes in the world won't fix the problem.
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Boble
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PostPosted: Sun Aug 14, 2011 11:33 am    Post subject: Reply with quote

Next thing would be to look for air leaks. Air leaks will give you higher rpms.

Cannot figure all out from your picture, but your SVDA distributor vacuum is connected correctly. The small vacuum pipe down at the intake looks like it's plugged, it seems.

Are the small brass pipes (one or two) sticking out on the rear side of the carb plugged?

Check the intakes for loose or broken rubber, and that the intakes are bolted firmly to the heads. Also, is the carb fitting tightly to the intake?

(Probably nothing to do with the high idle speed, but considering a stock air filter with a vacuum operated flap will make your engine run better)
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Ruffturn
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PostPosted: Sun Aug 14, 2011 11:58 am    Post subject: Reply with quote

Boble wrote:
Next thing would be to look for air leaks. Air leaks will give you higher rpms...


Air leaks below the throttle plate on a carbureted engine will only give you high idle if you are compelled to crank the idles speed screw enough to overcome the leanness. Otherwise, a vacuum leak will cause rough idle and stalling. Any air that does not go through the venturi will not contribute to the carburetor's ability to draw fuel from the bowl. Similar to how a newer FI engine is affected by any air that does not pass through the MAF.
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Boble
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PostPosted: Sun Aug 14, 2011 2:45 pm    Post subject: Reply with quote

Ruffturn wrote:
Boble wrote:
Next thing would be to look for air leaks. Air leaks will give you higher rpms...


Air leaks below the throttle plate on a carbureted engine will only give you high idle if you are compelled to crank the idles speed screw enough to overcome the leanness. Otherwise, a vacuum leak will cause rough idle and stalling. Any air that does not go through the venturi will not contribute to the carburetor's ability to draw fuel from the bowl. Similar to how a newer FI engine is affected by any air that does not pass through the MAF.


True, indeed.

What happened to me, though, was an air leak through the thermostatic vacuum switch system on the air filter caused higher rpm. Trying to compensate with adjusting messed things up. All carburater ports not in used should be plugged.

That said, I also had an incident with a worn out throttle shaft, causing wrong air/fuel mixture (actually the idle circuit below the trottle plate not fully employed, fuel/air leaked past the throttle plate). I plugged the small hole in the plate. Fixed the bug, and I have perfect idle now. However, I beleive this is a little "further down the road".

Also, another incident was a bad throttle spring, not giving full return, the throttle was left just very slightly open. New spring, some lubricants, and readjusting the acellerator cable fixed that. Another thing to observe...

One thing I have learned with these carburators: EVERYTHING has to be in good working order to make them idle consistently and right.

Good luck!
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traderpats
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PostPosted: Sun Aug 14, 2011 5:08 pm    Post subject: Reply with quote

I just got a rebuilt 34 Pict-3 from VolkzBitz and this morning I installed it in my 73 SB along with replacing the 009 with a Mexican Bosch svda. I couldn't get the idle down far enough with the Bypass Screw and it idled rough and erratic. To smooth it out the idle had to be set way to high. It think it was around 1200 or so.

I measure the hole in the butterfly valve and it was the larger size that is appropriate for a dvda. I did the rivet trick on the butterfly valve, being sure to punch out the left over rivet shaft, which reduced the opening nicely. Then reset the volume control and bypass screws and with the svda it now purrs like the proverbial kitten. If you had any noise around while sitting at a light it would be difficult to tell it was even running.

Anyways I don't know if the throttle valve was ever looked at but in my case that was the issue that skewed the idle.
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'73SB
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PostPosted: Wed May 28, 2014 10:00 am    Post subject: Reply with quote

Does anybody know how to get the idle speed up? I'm having trouble finding references about possible reasons for the engine to be idling too low / possible ways to get idle speed up. I can't get the engine in my 73 Super to idle past 650rpm fully warm.

Anyone know any common culprits or places to start looking? Or, threads / resources already discussing this that I can go back and read through?

Thanks
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ashman40
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PostPosted: Wed May 28, 2014 2:27 pm    Post subject: Reply with quote

Not sure why you revived an old thread that is basically the opposite of your problem?

You should create a new thread so someone with your same problem will be able to find the solution. It is not so intuitive to look for a different problem to solve your problem.
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