John,
One thing you can do that is easy is pull the spark plugs, rotate by the flywheel holding a screwdriveron the top of the piston & after finding top dead center rock the piston back & forth to see how much slop you have from top to a few degrees either way to check how much wear the rod has. the piston will show wear by not moving after top & reversing. A friend of mine takes rusted, pitted driveshafts & gets them hot enough to fill the pits with brass& sands them smooth. Holes & pits wlll destroy new seals. Yes it’s a soft metal & wears fast but a guy can get a few hundred hours out of the fix if you can’t find a replacement Support the drive shaft on a piece of angle metal to keep the shaft straight while heating & use flux to get it clean.
