Weber progressive adjustment issue - new to VWs

[MikeyM73]

Hi all,

I am new to VW air cooled engines but not new to cars and was hoping some of you might be able to provide some insight into an odd issue I am having. I have been into and built cars for many years, hot rods mainly but they all pretty much function the same, right? And please excuse any mis-spoken VW nomenclature that I may happen to spew but I will pick it up. So..onto my issue, pretty please.

The wife unit and I just picked up a '73 Westy type 4 that had been sitting in a field untouched for 10 years. It needs basically everything... including seats. Long story short, it has been converted to a center mount Weber progressive (I have read the pluses and minuses - my intake tubes do get pretty darn warm) but the carb on it was old, dirty, and shot, so a friend lent me one of his (same thing - 32/36 DEFV?? - electric choke model) which ran perfectly a couple years ago on a 1600 type 1 motor. This carb was not exposed to elemets but it was in a box and could have very well been knocked around over the years... no idea. So we got it running, set the time to 30* ATDC at 3k RPMs after I finally got it to idle.

Here's the issue - the choke needs to be almost closed for it to idle and sound the best AND I can turn the idle mixture screw all the way in until it seats and it still runs. When the choke is full open and engine warm, it leans out and I have to keep pumping the pedal to keep it running. So I'm thinking float level, perhaps? In playing with the mixture screw, it seems to be the smoothest (with choke almost closed) at about 2.25 turns out. I am very familiar with Holley, Carter, and Rochester carbs from old American V8s and have tuned them well. I'm just not familiar with this particular carb but have read they have 2 idle circuits / jets - something to that effect.

I found the redline weber site and set the carb per their instructions but what confuses me is why does it still idle when the idle mix screw is seated? It must be getting fuel from somewhere, I just don't know where that somewhere is. I read a great post from someone who had similar issues and noted there was a screw that metered the secondary idle jet?

The interesting thing is it runs very well with the choke damn near closed BUT smells very rich. So.. hoping one of you fine folks can point me to a site with base line specs regarding float level, and everything that can be adjusted on this carb. I have a feeling the idle jet(s??) may be too small. I realize this has been beaten to death but perhaps a quick note from one of you in the know will help.

Thanks very much for reading my blabber... I promise I won't be too much of a pest.

Mikey

[aeromech]

Sounds to me like your problem is more of a vacuum leak than a carburetor problem. First suspect is the brake booster vacuum line. If you really want to know for sure then do a smoke test.
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[borninabus]

the proper "adjustment" for a progressive carb is to remove it and install a proper dual carb setup or fuel injection.

welcome
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[MikeyM73]

Man.. thanks.. never even thought of that or blocked it off to check. I will do that right now and post back.

Thanks again.
Mikey

[MikeyM73]

Well, just disco'd the brake servo/booster vacuum hose, capped the orfice, and no change. it idles great when the choke is almost closed.

Note - when I open the choke plates a bit, it leans. But when I disco the cap below the throttle plates the idle goes up, as if it needs more air, but the faster idle is a bit choppier.

I will continue to fiddle with it.

[orwell84]

There is another screw that adjusts, I think, the fast idle cam. Its hard to explain, but it can cause the linkage to get stuck if too far out of adjustment. I figured it out by pulling the carb and just playing with the linkage while adjusting the screw. It will make sense when you look at it. Also, I spent a lot of time making my own linkage with stronger spring so that the throttle cable was a straight pull and the butterfly closed reliably when letting off the gas. Before, it would sometimes close, sometimes not when letting off the gas, making it impossible to tune. I would check these things before messing with jets.

[MikeyM73]

Interesting, thanks. But do you think that may be the reason it still idles when the idle mixture screw is seated? I wouldn't think so but I don't know these carbs well yet.

Thanks,
Mikey.

[Wildthings]

If it has been sitting I would dump some FI/carb cleaner into the tank and let it do its work. You don't want to be fighting to tune a carb with a clogged jet only to have the jet clean itself at some point down the road throwing the tune off again.

Having the choke mostly closed is kind of like having the float level set way high and is going to override the idle system. If adding FI cleaner to the tank doesn't improve things, you may need to pull, inspect, clean, and maybe replace the idle jet. It can be replaced easily enough with the carb installed, especially if the carb is installed so the primary barrel is towards the rear of the car. Idle jets are available in .05mm increments.

[mikedjames]

The reason it idles without the idle screw being opened are at least two -

With the choke on, the idle throttle setting is performed by a screw resting on a stepped cam under the choke mechanism. This pulls on the vertical wire on the side of the carburettor which is attached to the throttle spindle and holds the throttle open. - you can see this going into one of the holes at the bottom of the throttle shaft assembly below.

So with choke on, the throttle plate is opened a fair amount - enough for 1800 rpm when warm on my engine. In this state the engine is running on the progression holes and the idle jet, and the idle mixture screw is not really doing anything.

The wire used can get worn and decide to sit in different positions each time the throttle mechanism moves, leading to different idle speeds with the choke on.

Then when the choke comes off, the throttle plate has a habit of wedging just a tiny fraction off closed. So the throttle is still open enough for the idle jet to provide fuel. Increasing the return spring strength on the throttle can cure this, as can a quick stamp on the gas making the throttle plate snap shut instead of gently closing it. (this shows up quite often as you coast down to a stop on the off ramp)

And the throttle adjustment screw needs only a tiny amount of movement to take the idle up into 1000+ rpm territory when again that mixture screw starts to give up ...


In the picture below you can see the relocated throttle return spring - I have since stretched that spring forward to the support for one of the choke mounting column.

This installation also features a 1:1.15 lever and linkage which increases stock throttle travel to give real Wide Open Throttle on the progressive, while lining up the throttle cable with the stock fanhousing tube.

http://thelatebay.com/index.php?threads/making-the-weber-dfav-32-36-carburettor-work.19121/
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[MikeyM73]

Cool. Thanks everyone for all the input. I think at this point I will just pull the carburetor and see what it is set up with, spray it out and clean it, remove the jets, set the float level, and start everything from scratch. I found a couple of really good resources for initial jet settings so I will try those and see how they turn out.

Thanks again,
Mikey