K&n

[EX400rider]

Im getting a K&N airfilter, do i need to rejet it??

[Quad Dude]

nope

[FoxMxRiders]

:huh

you should always rejet if you change something between the airbox to the exhaust

then you will need to rejet or a least check your plug color

[dpizz450]

I dont think you should need to unless it starts backfiring. Slap an exhaust on there then rejett it. :devil:

[bwamos]

Stock filter => K&N you will need to go up 2 main jet sizes from stock if you leave the airbox lid on.