I had a friend one time trade in a real badly faded CR125 dirt bike that had that whitened look and the dealership polished it up so it looked like brand new. When we asked them what they did the answer was they removed the decals and sanded it down with a real fine sand paper and used brake fluid, Bike looked like brand new with new decals. My buddy was pissed.
I would suspect that the stuff to clean the yellowing off headlights would work as well but I have nothing to base that on.
2012 Polaris Sportsman 800
14" Wrec Rims w/26" Sedona Ripsaws