air filters

[Ryan'07400ex]

I was wondering if a K and N airfilter is better than a stock one. Does it give more horsepower or any advantages?

[tyman2395]

yes the k&n air filter will add some hp. well atleast thats what i found. if you get it get an outerwears pre-filter and take the lid off your airbox

[racerdan24]

will the K&N work for him without a rejet...or can he just pop it in and run?

[NacsMXer]

Originally posted by racerdan24
will the K&N work for him without a rejet...or can he just pop it in and run?

You might be able to skate by if you leave the stock airbox/snorkel alone. But if you remove the lid, you'll most likely have to jet up a size or two on the main.

[racerdan24]

That is what i thought because i know the K&N will basically bolt on and utilize the stock box,snorkel etc....Thanks for clarifying that.

[alberto]

I ran a K/N filter stock exhaust and no jettin for over a year. I rejet the carb only after I upgraded to a YOSH full exhaust. It ran great and I could feel the gains just by changing out the filter.

[Ryan'07400ex]

I have heard they let dirt in more than a stock. Anybody heard of this?

[NacsMXer]

Originally posted by Ryan'07400ex
I have heard they let dirt in more than a stock. Anybody heard of this?

I know this for a fact. I used to run 2 K&N's on mine. They both let fine dust into the intake boot riding in very dusty conditions. I say they are a fine filter for anything other than dusty conditions, but they simply don't filter fine dust as well as the stock foam filter. That's why I switched to a UNI foam filter and haven't had any fine dust in the intake ever since.

[Bridgewater]

Originally posted by NacsMXer
I know this for a fact. I used to run 2 K&N's on mine. They both let fine dust into the intake boot riding in very dusty conditions. I say they are a fine filter for anything other than dusty conditions, but they simply don't filter fine dust as well as the stock foam filter. That's why I switched to a UNI foam filter and haven't had any fine dust in the intake ever since.

does sand count as fine dust?
if so i may do a little swap myself, dont go to often but i love the sand lol

[UNBROKEN]

Originally posted by NacsMXer
I know this for a fact. I used to run 2 K&N's on mine. They both let fine dust into the intake boot riding in very dusty conditions. I say they are a fine filter for anything other than dusty conditions, but they simply don't filter fine dust as well as the stock foam filter. That's why I switched to a UNI foam filter and haven't had any fine dust in the intake ever since.

i had the same prob with k&n they flow great but filter not so great i had the same fine dust in my intake boot when i put my foam filter back in , no more dust past the filter IMAGINE THAT :p either way if u decide to get k&N just remember you have to clean them more to keep there filter abilty half decent.

[NacsMXer]

Originally posted by Bridgewater
does sand count as fine dust?
if so i may do a little swap myself, dont go to often but i love the sand lol

Put an Outerwears on the K&N and that should keep sand from clogging the filter. Should do fine, just don't go riding behind someone else in plumes of dust...neither the Outerwears or K&N will do you any good there. But if you're wide open riding without much thick dust, you should have nothing to worry about.

[Bridgewater]

Originally posted by NacsMXer
Put an Outerwears on the K&N and that should keep sand from clogging the filter. Should do fine, just don't go riding behind someone else in plumes of dust...neither the Outerwears or K&N will do you any good there. But if you're wide open riding without much thick dust, you should have nothing to worry about.

u think i could run with the outerwears and a open airbox and still be good?

[NacsMXer]

Originally posted by Bridgewater
u think i could run with the outerwears and a open airbox and still be good?

Shouldn't matter with an open airbox. Just don't ride in thick dust. I would definitely suggest a foam filter if you do, or just don't want to chance it.

When I had a K&N on mine, I had an Outerwears on the K&N, open airbox, and another Outerwears covering the airbox. Riding in thick dust, the K&N let fine dirt through.

[Ryan'07400ex]

So are you all saying it is better to stay stock or go uni filter then?

[UNBROKEN]

def uni...

[NacsMXer]

Originally posted by Ryan'07400ex
So are you all saying it is better to stay stock or go uni filter then?

Yeah definitely go aftermarket if you go foam. Something like a UNI, Twin Air, Pro Design, Curtis Sparks, etc these are all good foam filters. They are all much bigger than the stock foam filter for better airflow, plus many have a dual stage design with 2 foam layers for extra filtration ability.

[Honda10]

all you need to do is buy an outerwears prefilter and or a outer wears airbox cover for the K&N. I myself rid in extremly dusty conditions.

[Ryan'07400ex]

Having two layers sounds good. How much do they cost though?

[rcatvrider]

About $40 for the filter and about $20 for the prefilter.

[Honda10]

well know the brand new K&Ns cost 60 at motosports and Rockymountain but you can get one at magic racing for 40. The outerwears airbox cover cost 19 at motosport and the outerwears prefilter is 12 on rockymountain.

[rcatvrider]

Hell, if k&n's cost that now might as well get a velocity. They come with a prefilter, adapter, and have a superior design. They can be found for 100 bucks for the kit.
http://velocityfilters.com/

[Honda10]

how is that a good deal you can get the K&N,prefilter and airbox cover for 19 bucks less. The velosity only comes with a prefilter.

[rcatvrider]

I'm just saying if you are going to spend that much, you might as well get the best setup the first time around. $19 is chump change in this sport.

[JDMThoughts]

Foam filters are way superior in filtration over K&N, that reason alone should be the only reason needed to buy any of the aforementioned foam filters. Any dirt that gets in, goes through the carb, which helps promote buildup and requires more cleaning. It then goes to the motor, you want your engine to be as clean as possible, the more crap that gets through the worse your engine performance and engine longevity becomes compromised.

Originally posted by JDMThoughts
Foam filters are way superior in filtration over K&N, that reason alone should be the only reason needed to buy any of the aforementioned foam filters. Any dirt that gets in, goes through the carb, which helps promote buildup and requires more cleaning. It then goes to the motor, you want your engine to be as clean as possible, the more crap that gets through the worse your engine performance and engine longevity becomes compromised.

you need to stop and so does eveyone else. does everyone ride in your same conditions? I think NOT!!! listen foam filters suck in the sand so guess what no filter is superior in filtration cause theres a different type for different terrain. K&N is best for sand no doubt. Prefilters make it best for dust too. Go ahead and run a foam open airbox lid in the sand and lets see how long you run before needing jetting changes, the filter gets so clogged by the end of the day your running rich.

[scuzz]

Originally posted by FoxHondaRider
Go ahead and run a foam open airbox lid in the sand and lets see how long you run before needing jetting changes, the filter gets so clogged by the end of the day your running rich.


He's 100% correct.

Open lid + Foam Filter + Sand = problems

[NacsMXer]

Just get a UNI filter, 30 bucks. You don't gain anything by running a K&N trust me.

[JDMThoughts]

Originally posted by FoxHondaRider
you need to stop and so does eveyone else. does everyone ride in your same conditions? I think NOT!!! listen foam filters suck in the sand so guess what no filter is superior in filtration cause theres a different type for different terrain. K&N is best for sand no doubt. Prefilters make it best for dust too. Go ahead and run a foam open airbox lid in the sand and lets see how long you run before needing jetting changes, the filter gets so clogged by the end of the day your running rich.

Is someone getting testy, who deemed you king. I merely gave my opinion and that's what this forum is for. The OP wanted thoughts on filters and he is getting them. Believe it or not your not the end all be all in the 400EX world. I live in an area where there is plenty of sand, and after inspecting my filters during and after rides, the K&Ns are letting dirt through. I had K&Ns before, and they don't particularly filter well for me, so I don't use them. First of all I don't recommend running an open air lid ever, You can easily get an outerwear cover setup like EHS makes or design something similiar. I'm sorry you don't like my opinion, but you know what I'm entitled to it.

[scuzz]

JDM,

FWIW I had sand on my intake with an open lid and a UNI...I even did a redneck pre-filter (panty hose)

LOL!

:eek:

[JDMThoughts]

That's funny redneck pre-filter. I am not saying sand can't and won't. I don't even advise using an open air lid myself, hence the reason I mentioned the EHS lid which I use on all my bikes.You get the open air lid without having stuff slip through the bike.

Originally posted by JDMThoughts
That's funny redneck pre-filter. I am not saying sand can't and won't. I don't even advise using an open air lid myself, hence the reason I mentioned the EHS lid which I use on all my bikes.You get the open air lid without having stuff slip through the bike.

even with the airbox lid on and the air just coming through the snorkel foam filter would need a clean every other ride. With the lid off forget it its like a dust/dirt magnet. It doesnt reel it would just stick in and bury itself inside