H30/31 PICT Idle Adjustment Problems

[Craig57]

I've read the multiple versions of how to adjust a two screw carb and understand how carbs work. This one has me stumped; I'm wondering if it's toast and needs to be replaced.

I've put a rebuild kit into this carb on my 1300 as it was leaking air something awful; just about all the screws holding anything together were loose when I took it apart!

With the engine warmed up and all of the other adjustments done I can't get the idle speed below maybe 1200 rpm. The large bypass screw is screwed all the way in. Turning the small volume screw out will smooth out the idle and screwing it in will make it stumble. There isn't much change in the idle speed though.

So, what do you all think? It seems to me that the hole that the bypass screw seats in is oversized and that would mean I have to replace the carb. What diameter should that hole be?

More information:
I just checked that the bypass screw seats on to hole by marking the taper with a Sharpe pen and looking at the marks after I screwed it into the carb. Seems to be seating all around in the hole.

[mukluk]

Most likely either your timing is over advanced, or you have a vacuum leak.
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1960 Ragtop w/Semaphores "Inga"

[Joey]

Is the screw on the throttle arm properly adjusted?

Is the choke fully opening once warm and the throttle screw sitting on the lowest sttep of the choke cam?
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Joey

‘60 Kombi - '74 Bus - '79 Panel - '65 Beetle

[Aussiebug]

My thoughts run like Joey above.

First set your fast idle adjuster on the stepped cam - it MUST be set to just touch the very bottom of the stepped cam then 1/4 turn more. Dont touch it after that. This sets the throttle butterfly open about .004" so there is a nice venturi effect with the idle and transfer ports right next to the edge of that plate - for reliable idling using the larger Bypass screw to set the idle speed, and the Volume screw to set the mixture.

The choke butterfly must be set so it JUST closes with the engine over-night cold, and it must be upright (or almost so) when the engine is fully warmed up.

Then you can adjust mixture and idle speed.
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Rob
Rob and Dave's aircooled VW pages
Repairs and maintenance for the home mechanic
http://www.vw-resource.com

[Craig57]

As I stated, I had set everything to spec, but I'll try the throttle arm set up again. I used a slightly different method than yours that I found elsewhere that said to use .003 inch feeler gauge to gap between the screw and arm and a 1/2 turn. I probably didn't get it gapped right.

Oh, and generous use of Brakeclean on the areas normally associated with vacuum leaks had no effect on the engine speed!