I am getting a used 400ex for sure at the end of my, i think it will be a 2002 or 2003 and i was wondering what should be the first thing i buy for it, mod wise? Like an exhaust and what kind? What after an exhaust?

 

The first best performace mod would be to get a pipe and K&N filter. pipe wise i would get one from a specialty company such as sparks racing, LRD, alba (just came out with one for 400ex), and other companys like that. also FMF has a pretty kick @$$ pipe the ti-4 and man is it loud. hope this helped

 

sparks, lrd, ct, hmf, etc. i wouldn't get an fmf unless it was really cheap.

after that you need to jet the bike.

following mods should be a cam and piston unless you ride on a track a lot then shocks should come before anything.

 

i didnt know CT Racing made pipes for 4strokes

 

check out ctracing.com