Applying the choke pulls gas through all the circuits of the carb, low speed, high speed, and even the power valve under sone circumstances. It sounds like your idle circuit is clogged up, and the only way you're getting any gas at idle is by strangling the airflow and creating vacuum everywhere in the carb. Try tearing the carb down and tracing the idle circuit passageways with a piece of soft copper wire to check for obstructions. Use a spray can of carb cleaner to flush out all the idle circuits, followed by massive volumes of high pressure compressed air. Then gently bottom out the idle mixture screw and back it out about 2 1/2 turns for an initial adjustment. Once the engine warms up, it should idle without the choke applied. Then you can adjust the idle mixture for the smoothest idle and/or the best manifold vacuum.
Jerry
