What do you find best for cleaning light corrosion from un-coated alloy? specifically my 1975 BMW R60/6 crankase. I have used a dilute solution of caustic soda in the past, but it's a bit extreme and not very nice to use. I have tried commercial 'alloy wheel cleaner' without a great deal of success. Any suggestions? Oh and for those among us so inclined, save the effort, I'll say it for you, spider web remover? wheelchair cleaner? just rely on the alzheimers and forget it's dirty? etc, etc, any other assorted, 'old farts on beemers' cliches.