With the choke working properly and a clean carb, it should not be necessary to pump the throttle. Hold the pedal slightly open, pull the choke knob out all the way, and crank the engine until it fires. Push the choke knob in partway to avoid flooding and let the fast idle cam attached to the choke linkage increase the idle speed. Within a minute or so the engine should warm up enough to open the choke all the way.
Jerry