jetting help

[hondaruler95]

well im thinking about buying a full big gun exhaust and was wondering what the jetting should be. Its an 03 400ex it has a k&n air filter and i dont know if you need this but i live in Northeast SD

[CJM]

Prob 152-155 give or take. Id buy 150-158 to be sure and play around with it till the plug is a tannish color.

Needle should be 3rd notch fro the flat part and the air/fuel screw should be 2.-2.5 turns out.

[hondaruler95]

thanks for the help

[CJM]

Your welcome. Remember thats only a probable guess because due to elevation, air temp and fuel used it could be different.

Stock is a 148 so the numbers I mentioned should be a good starting point. Check out the sticky (linked in my signature) for some helpful threads on the subject.