jetting

[cals400ex]

i have a stock 400ex. i have modified the stock exhaust and have 3 one inch holes drilled in the air box lid. i live in central illinois for altitude purposes. i am not sure what main jet to put in. i think i will need around a 152 main jet but not sure. i have a 40 pilot jet on order, but i am not even sure if that is the right size. i might later on remove the choke also. thanks for the help

[Dune Surfer]

sounds about right . check your plugt to make sure it is not to lean. I am running a 160 main at sea level. You might try a #42 pilot. good luck

[Boone]

With the mods you made,I wouldn't change anything.Without upgrading the filter, you wont gonna see any gains.
Boone

[Dune Surfer]

Boone is right you need a K&N and outerware, regardless with your mods you need to rejet. as soon as you changed the airbox and pipe you made it to lean. Remember more air more gas=more power. But if you run it to lean you will ruin your engine.