Need Advice for jetting.

Hello to all, I'm bran new to this forum. I recently bought a new 08 400ex and would like to add a K&N Power lid and Lexx slip on exhaust system for starters. Whats stumping me is what size jet to go with. I've done a lot of searching but haven't been able to get clear answers so I figured go to the pro's... you guys.


I live in northern Va. Temps range from 20 degrees F in the winter to 90+ in the summer.

My elevation is between 700 & 800 ft above sea level.

My stock jets are 148 main, and 38 pilot.

I know I'm going to have to go through trial and error but I would like jet size and or kit recomendations and what has worked for you guys/gals in the past.

Thanks to all

Dan in VA