Cyrille,
If the stop screw, the one that moves the linkage, is open more
than 1/2 turn, then the carb goes into the transition phase, and is using
very little of the idle circuit, the screw that goes into the carb body.
That may be why you can almost close the idle circuit screw.
Generally, the car should run with the linkage stop screw in about
1/2 turn from the point where it makes the linkage move. The needle valve
should be about 3/4 - 1 turn out from where it bottoms. Idle speed is
adjusted with the needle valve screw. On DGV Webers, virtually the entire
mixture required for idling passes through this needle valve orifice. Often
the mistake folks make is using the throttle stop screw as the idle speed
adjustment. It isn't. Opening that screw a little too far permits more
negative pressure to act on the transition orifices which are differently
metered.
This is contrary to how many carbs are adjusted, and is a source
of confusion.
I would suggest you re-install the original jets and try this.
Hope this helps.
Peter
=====
At 12:31 PM 2/23/2004, you wrote:
>Hello,
>
>I have a Weber DGV 5A (32/36) carb on my 78 Midget.
>
>I know that it is running too rich (emission, black plugs, smoke, backfiring
>...)
>
>I went to a friend's place and he has a cool TRANSPARTEN spark plug that you
>can place to replace an plug in your engine and SEE the spark, especially
>how yellow/blue it is! Really cool toy!
>
>Ok, so here are the results of the test:
>
>In order to be OK, I had to:
>Change the primary jet to 1.30 (from 1.40)
>COMPLETLY close the idle mixture (and increate the IDLE speed in order to
>avoid the engine stalling)!
>
>This seams to give a much better mixture (emission WAY low, plugs much
>better, no smoke, no backfiring)...
>
>However, I am not happy with the Idle setup and I plan to change the idle
>primary jet from the standard .55 to .50 or even .45...
>
>Does anyone has a similar setup and can tell me how their carb is tuned up?
>
>Thanks, Cyrille
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