The 1406 I bought used has some rough life to it, no where near shiny.

Are they made from aluminium, thus have oxidized over time to cause a blotchy look and thus can be polished or do I need to have it chromed or something?

 

They're aluminum.

 

Soak the whole thing in a bucket of gas. Then take an old toothbrush and clean it up. It WILL get like that again. If you already have it on the car jst sprayit down all overs with carb cleaner and then toothbrush it.

 

Carb cleaner leaves a dull grey/white residue though, you can polish it out but it will be hard to get the nooks and crannies of the carb.. i would just use an all purpose grease cutting cleaner like chomp.
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BTW carbs are VERY easy to remove so take it off and clean it

 

Take it off, disassemble it, and dip the metal parts in real carb cleaner (the stuff in a steel bucket, with a dipping basket) for about 6-8 hours and it'll be all clean again. Not shiny like new, but all the oxidation will be gone.