I "rescued" a 1982 R65LS from an individual in New Orleans, LA soon after Katrina and the engine and pretty much everything made from bare aluminum had a lot of white "fuzz" all over! I used various scrub brushes, Scotch-Brites, etc and Eagle One Mag Cleaner for Uncoated Wheels. This is an acid based product and it really got things cleaned up nice. Another cleaner that works well on cast aluminum is "Greased Lightning" at full strength. I put it in a spray bottle, squirt it on, scrub, then rinse. Do not let it dry...
Good luck and post up some before pics!