i have a 400ex with a wb eseries pro meg full system, k&n filter with precharger, 8 one inch holes drilled in the lid and they are plugged with filtered vents..... i have the K&N atv jet kit for my 400ex and the main jets included are: dj134, dj138, dj142, dj146, dj155, dj16, dj165, dj170 i already ahve the other stuff installed like the fuel needle adjusting washer, eclip just want to know what main jet size i should go with i live in north carolina in the coastal plain region about 2 hours from beach if i need to change any other jetting like pilot or air mixture please inform me thanx

 

I'd start with the 170 mainjet and see how it runs at full throttle. If it burbles go down one size until it runs smooth.