Thanks to everyone who thought about and made suggestions regarding my intermittent stumbling and then the it-will-only-idle problem. You were very helpful, like always!
It's been a week of daily riding and there have been no hiccups. It seems to be cured -- geez, I'm tempting fate by saying that.
The bike is old enough to get in bars and there's a considerable to-do list of things that I probably ought to deal with on it. Despite that, I got out the hedge trimmers yesterday, and the limb cutter, and the sunny day/rainy day series we've been having is really making the grass grow, and the gutters need cleaning and you get my drift.