Originally Posted by bmweuro
Clean them really well with a mag wheel cleaner or Purple Power using a green Scotch pad, wipe down with Alumiprep, warm them up either in the oven at a very low temp or put them in the sun fr a while and give it 2 good coats of paint. It will last for many year before you ave to re-due it or touch them up.
I painted the fork sliders on my '86 R80 a few years ago. Cleaned them as BMWEURO described and hung the sliders up in the garage door. I used a good heat gun to preheat the sliders be warm to the touch and applied several light coats, 4 or 5, with a little preheat in between coats to keep the sliders a little warm. (pretty warm to touch, but not too hot to hold). The result as a pretty durable paint coat that has withstood 6 years of mostly year round commuting and still looks good. I use a similar method on my valve covers.