I'll measure the bore and stroke tonight (thanks for the tip on measuring the bore through the exhaust port!!!). It cleaned up real nice and the compression is good.

Any guesses?

BTW - if there is any interest, I want to ask my inlaws for a list of the abandoned power equipment they have on hand. Perhaps I can help find a good home for some of the engines and help my inlaws recover the $ they have in the repair? Anyone interested? They said it's mostly line trimmers, not so much the more expensive saws and blowers...