Brad, I'm not an expert, but I keep learning, and reading the posts. I owned a 1978 express. It was a good bike,
Mine finally died, with very similar problems. I alwasy assumed it was the carb that had gone bad. I had a hard time finding parts, and the carb never made it back onto the bike. That was the end of that.
One thing that sucks about fixing mopeds, is it always seems like there's a moment of zen when it runs just fine and everything is perfect and then blubblubbuhbuhbuhblaaaah the moment of zen is gone, and your moped won't run.