Well here's the latest... The problem has gotten worse. It used to come back to life after several dying episodes. Not now, it will run a little ways then die, over and over. I went back in yesterday and changed the connection to the coil and the tach. When I installed the tach a couple months ago I used a cheap 2-in-1 connector that I had in the tool box. Thinking that may be the problem, Not.
When checking the spark, which I've done a half dozen times in the last few weeks, it would throw a yellow spark then occasionally blue. Thinking I didn't have the plug properly grounded the whole time, I went with the blue. Checked it again this morning and nothing but weak yellow spark. And the plug, which was brand new and only had 10 minutes of use, was coated with a dry black powder.
The battery is new and tests good under load, so that's not it. Went through connections, all look good. Never had to deal with these symptoms before, so not sure if this is the common death throws of a coil or TCI or??