Good question. I don't really know the answer, that's part of my frustration. I'm a mechanical engneer and tend to look at things logically. This particular problem makes no sense to me. As I mentioned, I took it out of the plane and put it on my test stand where I kept spraying it with starting fluid. It would run for a few seconds and then quit. It was nasty hot and I was getting exhausted. I really figured that there was something wrong with the carb. I finally put the starting fluid away and just kept flipping it. It eventually started, and since that time, it's started every time for me.

I could see the fuel line had an air bubble right where it attached to the carb and it wasn't pulling the fuel into the carb. That bubble finally disappeared, but I don't know what actually caused the fuel to start flowing. As someone mentioned before, perhaps the little flappers weren't flapping for whatever reason and then they finally started doing their job. Who knows?

It seems fine now.