I have a kfx 400 and dont know what I should put on my quad to make it best for racing trails. Anyone have any suggestions would be help.

 

your bike is already super fast, you might want to try upgrading your tires--and some good riding protection for yourself--GOT GLOVES?

 

Olemanmoses is right get you some new tires (i would go with razr),get you some good aftermarket skids,bumper and keep the stock length of your bike.For power get you an exhaust,air filter and rejet,then do alot of practicing and your set.

 

I recommend you go with 22" razrs or xtc holeshots in the rear and 23" in the front. (more ground clearance, 6 ply protection)

bumper
a good skidplate
full belly skidplate
nerf bars
barkbuster handgaurds
go 1 size smaller on the front sprocket
go 1,2,3 or 4 teeth larger on the rear (to compensate the larger rears and gear it even lower)
beadlocks if you got the $$
stearing stabilizer

full body protection of course