Stromberg CD carburettor adjust the choke operation

The choke cable on a Stromberg CD carburettor is connected to a cam lever which in turn, is attached at its centre to a special petrol metering valve built into the body of the carburettor. As the choke knob is pulled out, so the lever turns. The cam face of the lever contacts the throttle valve and opens the valve slightly to provide a fast idle.

The arm turns the metering valve spindle, which provides a richer petrol/air mixture to the carburettor.
Check that the lever lifts when the choke knob is pulled, and that the lever returns to its stop on the carburettor body when the knob is released.

Loosen the clamp that holds the end of the choke cable to the cam lever. Make sure the lever is against its stop, and reconnect the choke cable.

Pull the choke knob out and start the engine. It should run at a fast idle. If not, or if it is running too fast, adjust the screw that is attached to the throttle valve lever, and which touches the edge of the fast-idle cam lever.

Turn the screw clockwise to decrease the fast-idle speed and anticlockwise to increase it. When adjusted properly, the engine should run at about 1000 rpm when cold and first started under choke.