What size jets do i need since i drilled 6 1" holes in my airbox cover?
Thanks

 

I personally would have rejetted before I put the holes in butit probably doesnt't matter.
What altitiude do you ride?Try some of the older posts there are tons of questions pertaining to 400ex jetting.

 

I live in south-central Pennyslvania All the jets i have in it are the ones that came with it. i haven't been able to make any mods to it to make me change the jets so far

 

I put the front two clips underneath my airbox lid, went to 165 main, dynojet needle on 3rd groove, 3 turns out, 16t front sprocket with stock tires and it made a huge difference. I can now beat my uncle's stock 400EX. Especially on top end. Before I made the change, whoever got the better start would win the race. Now it's close the first 3 gears, then in 4th I start to pull away, and in 5th is where I really get him bad.

Steven