Yesterday, getting ready to re-adjust (again), I find that after a few pulls, the pull start is stuck. Piston seems stuck in the cylinder.
It turns out the bearing on the connection rod is completely smashed up.
Tiny copper "chips" are found all over behind the rear cover and in the cylinder. Not sure if the cylinder and piston have been damaged.
I will be visiting my LHS tomorrow.
Perhaps this is the cause of all my troubles. Maybe somewhere there has been an obliquity right from the beginning?

to be continued....