So $600 to save 3.9 lbs.... what a deal! HAHA
If you're drag racing you could take the fender off (I know some tracks won't allow this but MOST will) and you save 5lbs for $0.
If you're doing anything other than drag racing, it doesn't make sense to run a CF fender. Even in MX, if you break a fender off and get mud/dirt coating your goggle lens you might crash or at least can't race to the full potential.
No arguement (at least a not a name calling, mud throwing arguement) here. I am wondering why you would want to run a real CF body panel on a quad. I'm also acknowledging that sheeblast is correct, road racing cars (and some rally cars) do use carbon fiber for some crucial parts.
I'll also point out that most do not use strictly carbon fiber either.
Most chassis' are a CF, fiberglass, and aluminum layered honeycomb monocoque frame.
Carbon carbon brakes are not carbon fiber like the original poster is talking about. Carbon fiber is long strand carbon blend (graphite being the main component) cross woven into a fine grade cloth and then "glued" together using an epoxy resin. Pure carbon can withstand about 6,000K before it sublimes BUT the resin is only good for about 600 degrees F before it begins to oxidize. Carbon fiber, therefore, is a poor choice for braking components.
Carbon carbon brakes are a mixture of pure carbon/graphite mix for the pads and a carbon fiber silicone carbide matrix for the rotors. The silicone carbide acts as a binder and is able to be machined like a steel rotor.
Last but not least, carbon fiber body panels... Have you seen a race car wreck? See what's left after what looks like a bomb went off inside it? The body shell comes completely apart and "brooms" leaving virtually nothing that resembled the car it once was. Would you want your fender to do that the first time you smacked something hard enough to crack the resin?