Progress Report: Put in new flywheel key & put everything back together. Tried to start it w/ the key & just got a click. Pulled rope, & it seemed like I had a compression problem like I had before. Maybe pulling & turning the flywheel threw something off; I don't know. So I adjusted the valves again, then pulled the rope. No start, but the compression problem seemed to be solved. Sprayed some starting fluid into the air intake, pulled again, & it started! ? Only ran for a few secs. before it died, but that's definitely progress. Sprayed some more starting fluid, pulled again, & it started again. Same thing as before, though: only ran for a few secs. So I guess now it's something to do w/ the carb., maybe. Guess I need a new battery, too.