is there a cool air supply to the carb at all? If not it could be just recirculating hot air coming off the cylinder. Poor fuel draw usually shows up as hard to start on a gasser as even with the choke it will be slow to draw fuel. How many flips with the coke on and cold engine does it take to get her to pop? My DA 50 would usually pop between 6 and 8 flips. Remainer of the day was choke off and 1 to 2 flips. It may be that the clunk line inside the tank had dropped off or has a split.