Mine would do the same thing. Even after sitting a day or 2 between starts, I had to feed it some juice down the carb to get it started. When I had my sending unit replaced, I also replaced the 40+ year old hoses (filler and vent hose). After having that done, starts like it should. The hoses looked pretty bad after 40+ years. Only thing I can figure is that maybe there was a crack that was causing vacuum to be lost, or maybe it was something to do with the sending unit. Anyway, it worked.