I have spent hours polishing the aluminium on the side covers, forks and rocker covers on my cb 650 and I can get them to a finish that you could use them to shave in. The problems I'm having is there is what looks like a black spiderweb through the aluminium, which no matter how much sanding, buffing or polishing I do I can't remove, and the other problem I'm having is more weather related, with all the rain we are having here, I have to polish the aluminium nearly everyday to stop it getting 'white frost' all over it. I have tried using car wax on it to stop the oxidation, which helps but doesn't fix the problem. I have checked with the local bike shops but they can't offer any useful information. I have searched the forum and the products that are listed I haven't been able to find, or find a supplier of in Australia. The polish I'm using is California Custom Purple Polish,
http://www.californiacustom.com/purple_metal_polish.html . I've almost had enough of the constant polishing and am about that far away from just painting the covers silver.