While restoring my CL200, all the aluminum had to be refinished: the engine side covers, wheel hubs, and fork tubes. Honda originaly covered them in a clear coat to protect from oxidation, but over the years that clear coat turned yellow, and any scratches and nicks allowed oxidation to creep in and crawl around. The result was a very ugly, very tarnished surface. 
First I used my Dremel with scour bits to remove the existing surface. You want the black scour pad bits, the brown ones are too rough and the purple ones are not rough enough. 
Then with all the old finish and oxidized aluminum removed, I used the purple scour pad bits to remove the deep scratches left by the rougher scour bit. 
Next, I hit it pretty hard with #1 steel wool to remove the scratches left by the previous step. 
Then I took a wad Eagle One NEVR-DULL, smeared it all over, then took some #0000 steel wool and applied some real elbow grease. This gave it a great consistent grey. 
Finally, I used Blue Magic Metal Polish to give it a little more shine. You won't be able to use the reflection of the aluminum as a mirror for shaving, but it's not bad if you ask me. The look I was going for was a consistent, aluminum grey. And I think I achieved it. 
Last but certainly not lease, I applied a thick coat of turtle wax. This does two thing: it keeps it clean, and, much more importantly, it prevents the aluminum from oxidizing. The purpose of the factory clear coat of the aluminum was for this purpose, it doesn't look as good but they can't expect people to was their bikes every year. So you must apply a coat of wax over the aluminum at least once a year! 