I don't know much about how these work but if you had hot fuel in the immediate area of the carbs could you pull the choke, dropping the nozzles away from the needle and push the hot fuel through the return with an electric fuel pump? Sorta like purging an nos system?

 

I see now the return is for excess fuel going to the carbs. The vent/overflow is for excess out of the carbs. 

I guess you'd have to plumb in some sort of purge tank for that to work.