OK, then. Another effort. I am getting better at this. I took the engine back to Mark and asked him how to get the gas tank out for a good cleaning. when I got home, I gave it a good scrubbing and found a lot of crud, but couldn't get into the carburator, and of course I couldn't start it, so I will try again tomorrow.

Lesson if the day: Engines aren't cool. They are smelly, noisy, and unreliable.