This stuff is about as poisonous and flammable as gasoline, but at least it's a good cleaner. I don't want to take apart or off. Spray it heavily with Gunk and leave it covered over night, then scrub with those plastic scratch pads. For the corrosion, Aluminum Jelly works good, but do it after you rinse the engine cleaner off. In general, the rough cast cases clean up pretty well with some aluminum cleaner or carb cleaner solvents available at auto parts stores.
Tide works OK, a brass bristle brush works really well.
You don't want to polish the cases with buffing wheel, etc. Polished side covers, like most of the older British and Italian bikes had, are fine, but polishing the engine cases themselves will cause the engine to retain heat. Finding someone to do this, however, is often a bit of a trick.