klutch,
ONAN Operating Manual calls for taking the load off the genny for a few minutes before shutting down. Like idling your road engine can stabilize temperatures across several dissimilar parts like head and exhaust manifold. I expect ONAN wants some of the working heat load off piston, cylinder, valves.
When a small engine has come to rest at exactly Top or Bottom Dead Center, it can be a bear to budge it off of there because of the geometry of the crankshaft.
SAR Tracker,
The Update was me, after going out to exercise our ONAN, finding a dead house battery, and checking for the crankshaft nut size while I was tinkering. CloudDriver mentioned his was hard to budge when stuck. Ours wasn't stuck just now and moved very easily with the short Craftsman ratchet and 9/16 socket.
We don't have an update from the OP yet.
