Hey I have a buddy with a 400ex and he is putting a K&N and LRD full exhaust.. and were wondering how we should jet it..

 

when i ran a slip on and a k&n i ran a 152. i would say start from around there and do a plug check to see where you need to go, dunno if this helped you much but at least it will give you a bump+

Wreckless

 

I was running a 158 with just a slip-on, open K&N, and Stage 1 Hotcam. I would probably start out with a 160 with an open intake. Also put the needle on the 4th clip. Maybe go up a size or two on the pilot, like a 42.