It's quite unlikely that the carburetor is physically damaged, Paul. The most likely places for a large air leak to occur, are between one of the diaphragms (fuel pump or metering) and the outside air. I suggest you check whether there is a wrinkle, or perhaps you've missed locating a diaphragm on one of the retaining pins, or there is a piece of dirt or old diaphragm on a sealing surface, or even the diaphragm itself is perforated. It is less likely you'd be able to hear an internal leak, such as a non-seating metering needle. Nevertheless, if you are opening the two chambers you should pay careful attention to the flap valves.
