I looked into getting these professionally polished and was shocked at the estimates I was given, I could purchase brand new carbs for the same price. So I searched high and low on the internet learning how to polish aluminum. Then I bought some old dirty scrap aluminum and started testing things out. This is the process I devised to do this as affordably as possible.
First get a rebuild kit with new o-rings, gaskets, floats, stainless fasteners etc.
These are available at a lot of places, I got mine at Ted Porters Beemer Shop. http://www.beemershop.com As long as they are apart you might as well rebuild them as that's a lot less time consuming than restoring and polishing them. Do them one at a time so you don't mix up the parts, these carbs are "chiral" meaning they are mirror images of each other and the parts are not all interchangeable. Here are the steps I took:
Completely disassemble carb, detailed instructional video is not mine - it is great https://www.youtube.com/watch?v=F4_C5B-SjFo:
Sand and polish all parts:
You will need the following:
10 kitchen sponges (stiffer the better)
Medium grit sanding sponge
Fine grit sanding sponge
200 grit wet dry sandpaper
400 grit wet dry sandpaper
600 grit wet dry sandpaper
1500 grit wet dry sandpaper
2000 grit wet dry sandpaper
Dremel or similar rotary tool
Dremel felts and wire wheels
Buffing Lathe (Harbor Freight - $75.00)
Orange, Yellow and White Cotton buffing wheels
Aluminum polishing paste
Completely de-grease and wash carbs, blow out all ports, jet housings etc with pressurized carb cleaner and soak in carb cleaner. I used a 1 gallon bucket of carb cleaner that I got at AutoZone.
Remove and dry off with a shop towel and allow all solvent to evaporate so sparks from the wire wheel don't set you ablaze.
Start off with the wire wheels and medium grit sanding sponge and sand sand sand.
Cut several small pieces off the sponge and use needle nose pliers to get into the tight spaces.
You can remove a lot of the casting imperfections (flashing from the molds) with a grinding stone if you want. Go back over these parts with the medium grit sanding sponge.
Move on to the fine grit sanding sponge and do the same as above.
Glue 200 grit wet dry sandpaper to kitchen to 2 sponges with waterproof Loctite® Vinyl, Fabric & Plastic Flexible Adhesive, let completely dry and then sand sand sand. Cut small pieces and use needle nose pliers to get into the small spaces. Repeat with the 400, 600, 1500 and 2000 grit wet dry sandpapers.
Polish with the red buffing wheel and aluminum polish:
then repeat with yellow and then white
Polish into small spaces with the Dremel felts and aluminum polish (with lots of pressure):
(Felts on the left. Wire brushes on the right were used at the beginning)
Wash with soap and water and nylon brushes. Ensure all small jet housings are free of debris before replacing jets (blow carb cleaner through all jet housings). Use a small straight wire to ensure overfill drain is not plugged and blow carb cleaner through it as well.
Estimate 5-7 hours to get a mirror shine on each carb, however the second carb will go a LOT faster once you've completed the first one and know how to do it.
Reassemble and rebuild carb, detailed instructional video is not mine - it is great https://www.youtube.com/watch?v=zxyC7wtS40w
There you go!
Best -0m3nc0w
