What mods really wake up the 400ex?

[Z400central]

What do? i want external, i dont really wanna do anything to the inside. thx:)

[DEAL]

Filter, pipe and re-jetting , a 14t front sprocket makes a HUGE diffrence in the way your power gets to the rear wheels , though with this mod you will loose a little top speed. You can also ground the welds out of the stock header, that makes a little diffrence.

complete pipe, no airbox lid, and a rejet will do the job..change gearing around also..

[Tommy 17]

just do the exact opposite from rico he doesn't know anything;) haha j.k

[BARRY]

I PUT A KN FILTER AND JETS AND A T4 EXHAUST AND MINE IS 100% BETTER THAN STOCK

[RideSportrax]

Here are the best mods I found for the 400EX:
K&N Air Filter w/ Outerwear
K&N Jet Kit
White Bros. E-Series Slip on Exhaust (The stock header is large enough)
Grind the Welds on the Stock Headpipe
Here are some tips: Switch to a 14T front sprocket

Create a free flowing airbox lid:
Get an outerware filter from K&N, then Take the stock lid and cut out the lid so you can attach the outer ware to the hole you cut out of the lid. This will create a free flowing lid with protection you get with the lid.