I painted mine with Krylon Fusion, it made them look new again initially but does chip and scratch somewhat. Not as big of a problem if you paint the same color.
Apparently a heatgun works, saw this the other day:
Yes, a heat gun set on high can easily/quickly restore faded bleached plastics. Its also an easy way to quickly melt your plastics too!
Short method...clean your plastics with soap/water. Take a small area, say approx 3"x 5", and begin using your heat gun to heat the area. Always keep the tip moving. Watch carefully as you continue to move the tip and you'll see the surface just begin to glaze over as the heat gun passes over. Once you see that you have heated the plastic enough. Make sure all area's glazed when the heat gun tip passes over. Turn off the heat gun and let the plastic rest about 15-25 sec. While waiting take a terry cloth and put a drop or two of auto polishing compound on the towel. Now lightly but briskly rub the just heated area. Turn the towel and buff lightly again...You'll have a nice shiny new surface that will only need normal cleaning. My plastic's stayed nice for about a year then I simply hit it them with the heat gun to freshen them up again. A little practice goes a long ways but I did all my plastics in less than an hour. With the KLR the front/rear fenders are much thicker than the fairing so be careful when doing the fairing...heat builds quickly.