Just curious if anyone has ever put a straight K & N filter on their quad and eliminating the airbox. I was thinking about doing it, and putting a prefilter sock sleeve thing over it, but didn't know it would still injest to much dirt or water. If so, what were the horsepower gains, if any? --Just curious

 

i run one on my 400 and the power increase is amazing.i dont ride in much water or mud so i dont really worry about it,if you ride water and mud alot then keep your airbox..

 

i run one too its worth it..make sure to get a prefilter though

 

I agree with all of the above statements.
Can't you just remove the lid and rejet for dry conditions and replace it when wet out?

 

If you remove the stock filter and air box be sure to look at rejetting your carb. There will be enough air change that you should go up a jet size.