Yep, that's the one!
And #1 and #2 in the drawing are the two adjustment screws I was referring to.
OK. Here's my stock carb adjustment instructions:
There is a lever on the left side (left is left side of car) with a cable connected to it. This is the Throttle Lever.
On the throttle lever is a small screw which sticks out towards the back of the car. This is the Idle Adjustment Screw.
The idle adjustment screw rests on a strange-looking flat piece of metal with steps cut in it. This is the Fast Idle Cam, and works with the choke to give a reliable idle on a cold engine.
The engine must be warm to set the carb, so that the choke is off, and the Idle Adjustment Screw is sitting at the bottom of these steps (at the BOTTOM, not on any of the steps themselves). Directly beneath the fast idle cam on the left side of the carburetor you will see a screw with a spring wrapped around it. This is the Volume Control Screw.
On the side of the carburetor body is a barrel-shaped object, about the size of a pen-light battery, with a wire connected to the outer end. This is the Idle Fuel Cutoff Valve (solenoid). This shuts of the fuel when you turn off the engine, to prevent 'running on'. Be sure the wire is connected and runs to the (+) terminal on the coil. (This usually runs off the same wire which attaches to the choke.)
Also make sure that this solenoid is screwed into the carb snuggly, and not rattling loose. Don't overtighten it though, it's got a fine brass thread and screws into aluminium - both quite soft metals. You can test the operation of this solenoid very easily. Turn on the ignition, and pull off the wire on the valve. Touch the wire on the connector, and you should hear a clicking sound as the valve inside moves. If not, check for 12 volts on the wire (small trouble light, voltmeter etc), and replace the solenoid if required - if it's not working, you won't get a proper idle, and you'll get rough running at traffic speeds too.
As stated previously, make sure your engine is warm and the choke butterfly standing upright. Make sure the air cleaner is ON when adjusting the carburettor--the engine expects it to be there.
Turn the Volume Control Screw in all the way - GENTLY PLEASE. It is a needle valve, and you don't want to enlarge the hole by forcing it home. Now unscrew it 2.5 turns. This is the starting point for the adjustment.
Start the engine, and turn the Idle Adjustment Screw in or out to set the idle at 850 RPM. I'll let you work out how to measure 850 rpm - but it's a fast idle. (See our idle adjustment procedure.)
Then turn the Volume Control Screw in slowly until the engine speed begins to drop, then turn it out until the engine runs at its highest idle speed. It should still be within about ½ turn from the start setting of 2.5 turns. If the hole has been damaged by a previous careless person, you'll just have to do the best you can. Now screw it in until the revs 'just' start to drop - about 30rpm. This is the final setting.
Reset the idle speed again with the Idle Adjustment Screw. Don't slow the idle too much, 800-850 is about right. VWs need a few revs at idle to keep the cooling air flowing, otherwise when you coast to a stop at the lights after cruising at a good speed, your hot engine won't get enough cooling air, and it won't like you very much.
(I didn't write this. It's an old instruction sheet I keep on file when I have to tune-up my Bug.)
Good Luck.
