Hi Reynoldston,
Thank you for your reply. I had tried several new plugs, BUT...
good news today - my friend looked at it, and he tried to start it with the same problem I had. But then he had me hold it in place while he held the throttle wide open and it ran like a champ. It looks like the idle screw might be too tight, because when he let off the gas it dies. He was able to start it a few times like this. How this magically happened that the idle went too low overnight is a mystery to me, but at least I have some clue as to what is going on!
Thanks again,
Mark