Hey everybody, I'm a bit new to ATVs so I thought I'd ask this question. I and my buddy have '01 and '03 400 EXs respectively and were looking into K&N filters for them. Firstly, is there any reason I would NOT want to go to a K&N filter, other than the price maybe. We ride a lot of different terrain, generally semi-dusty trails and mud/water holes, but ride very little sand. Would a filter cover be recommended?

Also, I've heard about punching the airbox on a 400 EX after the filter is installed. What exactly is this, and what does it do?

Thanks in advance, and sorry for the newbie questions...

 

Get a K&N air filter and an outerwear and you will be fine for whatever condition. By putting holes in the airbox, more air can get in to the motor, and therefore (after correct jetting) increase power. Or just take the lid off.

 

I have run K&N's + Outerwears in the desert for years with no problems. If you vent the lid, try the Uni or White Bros. filtered vents. They help keep it cleaner than just taking the lid completely off. But, if you run in a lot of water/mud you might not want to vent your lid at all.

And, you will need a rejet. Honda jets lean at the factory. So, you will be way lean after any mods.

 

my local honda dealer told me that a k&n air filter...not rejet just filter would void my warranty...they said they could tell if i had 1 on it even if i put the stock 1 back on it....any comments?

 

K&N filters are suppose to not void the warranty, second, how could they possibly tell what filter you had on. Do they hire a forensics team or something. I think this guy is talking out his ***.

 

One of the guys I ride with bought a 400ex new last year and installed a k&n right away. He is already complaining of oil usage and and a small amount of smoke. Next time we go I will do a compression test and check the intake tract. We have been riding severly dusty trails all summer .I mean trails so dusty you have to space each other out half a mile till the dust cloud settles so you can see. I used to use them a lot but I had several engines with prematurew wear. I have noticed on my factory foam filter it will look like hell on the out side but on the inside it is as clean and white as new. Again you guys should check out some of these web sites that are testing these things for air flow and filtering efficiancy. I still believe they would be ok for winter use or maybe in sand duning because the sand is large grain . But fine dust is another matter. Its your engine so a little research could be worth it.

 

I've been running K&N's with outerwears for a long time on both my rigs and have yet to have any problems, the 2 biggest problems with ANY filter is dirt, you need to clean them often, specially if you do lots of riding, the other problem is that thay are not seated correctly (bad mounting). As usual it is about preference, whatever that person likes best, or what their friends tell them is best. I won't go back to oil soaked sponges.

 

just stating what my local dealer said to me.....they said their tech's could tell if i had been running a k&n...i don't see how either......is there a noticable difference when you add a k&n?

 

Vampire,
Dont worry, I didnt mean that you were talking out of you rear, I think the dealer guy was.
IF they can tell, they are special people

 

lol maybe the guy checks the engine and see its very clean and say hes been using k&n

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