It just occured to me that you could have a misadjusted choke vacuum pulloff. When the motor is cold and not running, a single depression of the accelerator pedal should open the throttle and the choke thermostat should shut the choke fully. At the same time, the fast idle cam linkage should pull the fast idle cam up under the fast idle speed screw. As soon as the engine is started, the choke vacuum pulloff should open the choke ROUGHLY 1/4 inch, but the fast idle linkage should be adjusted so the fast idle cam stays under the fast idle sped screw. As the motor warms up the choke thermostat slowly pulls the choke the rest of the way open and the fast idle cam is slowly lowered until the carb controls idle speed with the curb idle speed screw, not the fast idle cam. If the vacuum pulloff is misadjusted, it can open the choke completely as son as the engine is started. This defeats the choke and fast idle functions of the carb.
