Hot water [even boiling!], with a dash of any shampoo, is what I'd use. Rinse off with more hot water. Then blow out the nooks and crannies with compressed air.

, Shampoo? It isn't alkaline [and therefore corrosive to aluminium alloys], unlike many detergents, and rinses away very easily, leaving no residue. A trick o' the trade my motorcycle mechanic put me on to.