me & my brother boyh have 400exs , i just bored mine to a 426 with a 12 tooth front sprocket and his is pretty much stock with a 13 tooth front sprocket with a k& n air filter , but his has alot more bottom end -can it be the air filter?

 

A K&N will increase performance....but at what cost???? They pass very fine dirt particles, plain and simple!!! I know this form personal experience.

A better choice is a ProDesign (ProFlow) adapetor and foam filter. You will get better performance, but still not have to risk reducing your engine longevity.

 

K&N means better air flow,unfortunately that also means better dirt flow,the two go hand in hand no way around it. Not so bad with cars,street bikes,sleds or boats but very bad for ATVs where there designed to play.

 

<div class="FTQUOTE"><begin quote>Originally posted by: reconranger

A K&N will increase performance....but at what cost???? They pass very fine dirt particles, plain and simple!!! I know this form personal experience.



A better choice is a ProDesign (ProFlow) adapetor and foam filter. You will get better performance, but still not have to risk reducing your engine longevity.</end quote></div>

Could not have said it better, my friend.....I had the problem with my 400EX....switched to a Pro Design, less performance than K & N, but more than stock.....

 

thanks for the advise ,ill have to get me one

 

ive had a K&N on my 06 hawkeye for about 8 months now and no problems for me, i also bought a foam pre-filter like the stock one to put on it though to help with some of the dust. i ride in mud, water, deep dusty sand, and on road and i have had no problems with it at all, but i bet the foam prefilter helps alot because i clean that every 1-2 months.

 

What about UNI?


I have a K&N on mine.