there is a product out for restoring scratched up and dull atv plastic, but we tried it on my brother's 250ex and didn't have good results. It looked shiny and clean for a while, but it puts a clear film of plasticy stuff on your fenders, which peels off eventually some spots and stays on other spots and makes the whole thing look like a sunburned fat guy, so I wouldn't recommend trying that. I don't know of anything that actually works, but someone else might.