After watching numerous videos, here's what worked on my Craftsman garden tractor: If starter turns flywheel (and debris screen visible on top of the flywheel), but only turns part of a rotation, and maybe the flywheel turns in reverse a bit, then the cylinders are probably locked; compression cycle on the cylinder(s) is stronger than the starter power. To solve short-term: Remove the spark plugs. This releases the lock in the cylinder(s). With the spark plugs removed, spin the flywheel (via the debris screen) by hand. If it turns freely or with very little resistance, then turn the starter and the flywheel should rotate freely. Reinstall your spark plugs (and wires), and try the starter. Mine started right up. That solved my problem short-term, so I could get my immediate task done. Long-term, consider checking and adjusting the valves, or having a professional small engine shop diagnose the problem further. DIY instructions: https://www.youtube.com/watch?v=zJlYQ19W...