i have an 03' 400 ex. And i want to modify my air box. Does anyone know what the proper jetting should be.. thanx guys

 

Depends on how you modify your airbox, ie: how much more air flow you are gonna get by the mod you do to it. It will also depend on your elevation.


Your question is way too vague to answer.

 

modify the lid ride it check the color of plug if its coco brown your good if its white go up five like 135 to 155 and so on if is black go down it just takes some playing with or you could take it to the dealer and they can do the same thing for 55 big ones an hour

 

all i really did was put four prefilter plugs on the lid.. and i also want to take out my spark arrester (baffle) does that help any

 

it won't help much. put in a 150 keihin mainjet. stock is 148.