My generator cover cracked as well but I managed to get it welded - just needed a bit of dressing on the gasket face (see pic). However, I've used JB weld in the past - the high temperature version to glue on some cooling fins on the barrel of one of my other motorcycles after I snapped it off when I removed the block from the crankcase. It has proved extremely durable and after filing down, dressing and painting, not even visible. As long as you completely degreased before using it, I would think its probably as good as a metal weld for this type of repair.