I just recently purchased a new 2005 Honda 400EX and was thinking about replacing the stock air filter with a K&N air filter.
Was wondering if i have to do anything as far as carb adjustments go,or can i just install it.
Any info would be much appreciated. [img]i/expressions/face-icon-small-smile.gif[/img]

 

I think you are in the wrong forum (just like me). First off, my experiences with K&N's is that they will absolutely pass very fine dirt! I say don't do it!

Get a ProDesign (ProFlow) aluninum adapter and foam filter, and run without an airbox lid or better yet run the EHS Racing Outerwears lid (unless you are in the wet all the time, then you will be forced to keep the lid on). You will need to rejet.

 

If you buy the Kand N filter it works good as long as you keep them oiled and service right.
You should not have to rejet with just a filter in it.

If you go to the aluminum adapter and then use a cone filter with no box then yes you will have to rejet the carb.