493 hard to start when warm

Pull the coil high tension wire and ground it to kill the spark. See if it cranks. If so, it's not compression, battery, cables, or the starter. Its way too much timing advance

If it still does not crank it could be most any of the above. Start by looking for hot spots in the cables. Connections. You need to scare up a "carbon pile" battery load tester, which will allow you to measure both starter load draw, and to load test the battery

Are you sure the charging system is keeping it up?