I'm going to chime in because I have a similar problem. Usually, if I crank within a couple of days she will start up fine. If she goes a week or so without running, she will turn over till I run the battery down without even sputtering. The carburetor bowl is vented to the atmosphere. That bowl doesn't hold a lot of fuel. It doesn't take long, especially in hot weather, for that fuel in the bowl to evaporate. It takes awhile to fill that bowl back up, with that old diagphram fuel pump. So, the engine turns and turns and turns. So, I've learned that if I haven't cranked her in more than three or four days, I must remove the air filter and pour about a shot (ounce or more) of fuel straight down the carb. She will fire up and purr like a kitten if I do that.
