Muriatic acid will dissolve the welded on aluminum on the crank throw. Just soak it for a bit, in a well ventilated area. You need the crank out to do this and you will need it out to measure the bearings properly anyways. I did a kohler a couple of years ago. Took about half an hour. Another tip, When you mike the bores, be sure to measure at the top AND bottom of the cylinders in both directions. Onan cylinders often wear even more egg shaped at the BOTTOM of the bore due to rod angularity mid stroke.