get mothers plasic polish
clean everything all nice and good then polish it with this stuff http://store.bikedepot.net/moplpo.html
taken from site above...
Mothers- Plastic Polish was formulated to clean, shine, and protect plastics and clear plastics. It is highly versatile and can be used on anything from the plastic gauge cluster cover on the instrument panel to the black plastic engine casings. The best part is it actually beautifies these sometimes finicky surfaces by filling in and buffing out little nicks, hairline scratches, and tiny flaws as it cleans the surface, freeing it of smudges, dust, and fingerprints. Mothers- Plastic Polish is a true polish, and can tackle even the seemingly baked on ˜yellow film and ˜cloudy streaks from the most sensitive plastics. The tough cleaning combines with a gentle polishing process that, while it removes all the undesirables, leaves the surface sparkling. Clean, clear, and bright and on motorcycle plastics, what more could you ask for?
How about lasting protection? Mothers- Plastic Polish does a lot more than make the surface look pretty; its a strong protectant as well. Regular use diminishes the harmful effects of sun, smog, water stains, and airborne contaminants. Armed with tough and effective polymers Mothers- Plastic Polish acts like a shield, defending your plastic surfaces from the ravages of the elements and daily riding.
When your serious about protecting and beautifying every part of your bike look for the Plastic Polish serious detailers and hardcore enthusiasts use when perfecting their own rides. Order Mothers- Plastic Polish the most effective plastic polish on the market bar none.