I know I shouldn't say this but that was going to be my second guest, the metering needle being stuck or to open, because you mentioned that it would only run after choking then it would sotp, that means no fuel through the metering needle, and then when the metering lever that lifts the needle is to high you thend to overflood the carb and thus the high needle is hard to set. I hope that the changes that you did work out for your engine. Good luck