Is it that bad to run a K&N ?

[Honda.rider5871]

I recently found a really nice 07 400ex to replace my 04 , The guy says it has a K&N air filter , White bros pipe(not E-seires) , jet kit, itp c series wheels with holeshots , full skids, pro peg nerfs and bumber , anyways im gettin it for a good price . I was wondering if the motor could be damaged at all from running a K&N .

[AtvKid4Eva]

Its a heated debate. Some say yes, some say no. Ive ran a properly oiled K&N with an outerwear for years on both my old 400 and now my 450 and have never had a problem. Have ridden in some heavy dust too. Maintenance is key. If your worried about dust run a UNI.

[fish22]

not to highjack this, and at the risk of sounding retarded....but do you have to oil a UNI? and can you buy a uni in a normal ole automotive store?

[Honda.rider5871]

Im planning to switch filters to UNI when i get it , It just has me a little worried on how bad the K&N was on the bike for the time its been ran in it.

[kbnorth99]

My '06 ex has a K&N. The guy I bought it off of said in installed it first thing. He raced desert races out of Central CA. I ride it pretty hard on track, trails, sand, and very dusty conditions. I have never had an issue. My motor runs great with almost 300 hours on it. And I have never found any dirt, dust, sand, or any other foreign matter inside the intake. I'm not sure what the guys are doing that have had trouble with them me and my brother run k&N on everything we ride without a single problem ever. 6 quads and 3 bikes all running K&N and all of them run great.

Like Atvkid said its a heavily debated topic. I consider the K&N to be a good thing. I would buy a quad with a K&N or a UNI before I would buy one that has run a stock filter. I would say buy it. But that's just me.

[AtvKid4Eva]

K&N's flow great and theres no problem if you keep them oiled and cover with a pre filter. and yes you have to oil a UNI.

[Honda.rider5871]

Looks like ill be taking it home sunday if it as nice as it looks in the pics , thanks guys . Ill post soem pics when i bring it home if anybodys interested.

[smorris1]

I have a K&N too and it does great. I run it with a outerwear as well and that keeps it waterproof as well as keeps the fine dirt out.

[0101]

I run a K&N on my 400ex and 450r.

The last time I tore down my 400 carb, the butterfly valve was caked with dirt. The intake tub was coated with a thin layer of dust as well.

We always properly clean and oil our filters and always end up with filthy results. However, I do partially blame it on the conditions I ride in, which are likely among the dustiest conditions (powdery dust) in Northern California.

Im finishing up a fresh rebuild on my 400 (416) and will be switching to a UNI filter. I had a UNI on my old 300ex, and the difference is phenominal. I there was NEVER dust in the intake tube or the carb. Nothing beats a UNI in my opinion.

[NacsMXer]

Originally posted by 0101
I run a K&N on my 400ex and 450r.

The last time I tore down my 400 carb, the butterfly valve was caked with dirt. The intake tub was coated with a thin layer of dust as well.

We always properly clean and oil our filters and always end up with filthy results. However, I do partially blame it on the conditions I ride in, which are likely among the dustiest conditions (powdery dust) in Northern California.

Im finishing up a fresh rebuild on my 400 (416) and will be switching to a UNI filter. I had a UNI on my old 300ex, and the difference is phenominal. I there was NEVER dust in the intake tube or the carb. Nothing beats a UNI in my opinion.

X2

I used to run K&N and had the same results with the intake tube and carb caked in a fine layer of dust.

It bugs me when people say, oh if you maintain them properly, they don't let dust through. That's not the case in my experience as I maintained my filters very well. It depends a lot more on the conditions you ride in and the TYPE of dust. K&N's WILL let through very fine dust, they just don't have the surface area to be capable of stopping everything. It's just a thin layer of cotton gauze, it's weaved together so it has random size holes in it. The finer dust gets inside the bigger sized holes.

I switched to UNI foam filters and haven't looked back. Since then I have never had any dust in the intake. Foam air filters are a lot thicker, and many like the UNI are dual density foam, so you have two layers of stopping material that the dust has to weave its way through (where it is trapped). With the K&N you just have this one very thin layer so a lot of junk gets passed through it. I don't care what foam filter you run, UNI, Twin Air, No Toil, Sparks, etc. they will all filter dirt better than a K&N hands down.

I only recommend K&N filters for people using them on the street, drag racing, or other low dust conditions. For everything else on a quad you are compromising your motor if you continually pass fine dirt through it running a K&N. The way I see it, the job of an air filter is to filter the air as best as it can. Why would you want to run an air filter that does a poorer job of that?

[AtvKid4Eva]

Nacs did you have an outerwears? just curious.

[0101]

I have an outerwears on my 450r and am seeing similar results to the 400 without the prefilter. My prefilter gets clogged easily too.

For the record, I am not rebuilding my 400 due to any problems caused by the K&N.. I just want more power lol.

[coryatver]

got to love people say you need a prefilter why do you need a filter for a filter haha. Only time i would run a K&N is sand dunes. If you got a good deal I wouldn't worry about it. Put in a uni or twin air filter, clean the carb, change the oil and you should be good to go

[NacsMXer]

Originally posted by AtvKid4Eva
Nacs did you have an outerwears? just curious.

Yes, I had an Outerwears on both the K&N AND the airbox as an airbox lid. Doesn't get more overkill than that.

The truth is, is that the Outerwears protect the K&N from prematurely clogging up with larger dust particles, pieces of dirt/mud, things like sand, and add water repellency so the filter doesn't get soaked. But they will do absolutely nothing for fine dust, if the dust particles are smaller than the pore sizes in the Outerwear. And that's what I saw, lots of fine dust went right through them and the K&N.

Now I just have the Outerwears as an airbox lid, and a plain UNI foam filter. It filters so much better it's not funny. I even bought a custom Outerwear to put on the UNI but the UNI works so well by itself I haven't found the need to use it yet.

[slightlybent47]

With a K&N you are running a risk of having issues. At ½ to 1 HP gains with the K&N is it really worth it.

Is that ½ -1 HP going to win you any races? NO!
If you think it will I have a ski resort in Texas I’ll sell you real cheap?

Run a foam filter with plenty of filter oil on it. Oil is the key to trapping the dust.
Running a high flow air filter in extreme dusty conditions is not a good thing unless you have plenty of money for rebuilds. If you run with the lid on and the snorkel in place then you defeat the purpose of the high flow filter. If you run without the lid, then you need better protection.

The gain is not worth the risk.


A properly oiled foam filter work best for trapping dirt.


Let’s take a look at what a high flow air filter is. In an effort to increase air flow they use a thin paper or cloth type filter instead of foam. Then they pleat the filter in order to increase the surface area.
Now you have a filter that flows better but it comes at a cost.
The K&N or any type of pleated paper or cloth filter dose increase air flow.
How do the do that?
They make the holes larger; you can hold the K&N filter up to a light and see all the huge holes in it.

Now let’s look at what happens when a filter gets dirty.
With a K&N filter the surface gets covered in dirt, and some gets through.
After the filter get dirty it flows much less because the flat surface gets covered and it clogs up the holes, reducing air flow.

Once the K&N get dirty it defeats the purpose of using the filter in the first place.


With a foam filter it has many more holes in it. But the best advantage is that the air has to weave its way through the filter. When it weaves through the filter it gives the dirt a better chance of contacting the filter oil and getting stuck in the filter.
Plus when it gets dirty it still flows well because it has many more ways to get through.

K&N filters flow better, no argument there. But they don’t trap dust and dirt as well as a foam filter.

K&N clams there filter flows better, and it does. But they don’t clam it filters better.

[CJM]

I run a UNI in a sand pit, I also have an outerwears lid. The filter and lid can be filthy-but the carb is ALWAYS clean as a whistle. I use PJ1 foam filter oil, I clean the filter like every few rides with some gas and then spray it up. I tried maxima filter oil in a bottle but what a freaking mess it makes.

My friend has a KN on his 450R, his hasnt blown up yet from all the dust-but strangely enough the thing is needing rings and the rings were only done maybe a year ago along with a full top and bottom rebuild. Yea it has tons of hours on it-but its odd that the cyl is also worn a bit too. Mine has about the same amount of hours and its clean as a whistle.

btw just for kicks listen to this short story: I sunk my quad in the sand pit, they have a huge sand lake that is dredged and has like a 2ft shore. Well It was in the water for awhile and I had sand in everything to a degree. But funny thing is although the carb did have sand in it-it wasnt nearly as much as everything else. Did the UNI help, IDK but I like to think so.

[NacsMXer]

Originally posted by slightlybent47
With a K&N you are running a risk of having issues. At ½ to 1 HP gains with the K&N is it really worth it.

Is that ½ -1 HP going to win you any races? NO!
If you think it will I have a ski resort in Texas I’ll sell you real cheap?

Run a foam filter with plenty of filter oil on it. Oil is the key to trapping the dust.
Running a high flow air filter in extreme dusty conditions is not a good thing unless you have plenty of money for rebuilds. If you run with the lid on and the snorkel in place then you defeat the purpose of the high flow filter. If you run without the lid, then you need better protection.

The gain is not worth the risk.


A properly oiled foam filter work best for trapping dirt.


Let’s take a look at what a high flow air filter is. In an effort to increase air flow they use a thin paper or cloth type filter instead of foam. Then they pleat the filter in order to increase the surface area.
Now you have a filter that flows better but it comes at a cost.
The K&N or any type of pleated paper or cloth filter dose increase air flow.
How do the do that?
They make the holes larger; you can hold the K&N filter up to a light and see all the huge holes in it.

Now let’s look at what happens when a filter gets dirty.
With a K&N filter the surface gets covered in dirt, and some gets through.
After the filter get dirty it flows much less because the flat surface gets covered and it clogs up the holes, reducing air flow.

Once the K&N get dirty it defeats the purpose of using the filter in the first place.


With a foam filter it has many more holes in it. But the best advantage is that the air has to weave its way through the filter. When it weaves through the filter it gives the dirt a better chance of contacting the filter oil and getting stuck in the filter.
Plus when it gets dirty it still flows well because it has many more ways to get through.

K&N filters flow better, no argument there. But they don’t trap dust and dirt as well as a foam filter.

K&N clams there filter flows better, and it does. But they don’t clam it filters better.

Pretty much summed up everything I was getting at.

A lot of people don't understand that foam is superior in it's filtering abilities because of much more surface area...it's quite simple.

The more the air has to weave it's way through the filter, the more chances there are for dirt to stick to the filter oil. In other words the filter media is more efficient in function. With the K&N's it's more or less a straight shot through a thin layer of cotton gauze, and the particles that are smaller than the irregular holes in the cotton will get through. The other particles will stick to the oil, but it's nowhere near as efficient as foam overall.

[DnB_racing]

if your running dusty areas I run the foam , but muddy watery areas I dont like the way the foam holds the water and chokes out the carb, and muddy dirty water will pore into the carb,

I have both the K+N with drywear outer and the Uni well oiled, depending on were im riding I will use the appropriate one...

They both have ther place!!


foam in dirty water is bad and k+n in dusty conditions are bad,

[slightlybent47]

Originally posted by DnB_racing
if your running dusty areas I run the foam , but muddy watery areas I dont like the way the foam holds the water and chokes out the carb, and muddy dirty water will pore into the carb,

I have both the K+N with drywear outer and the Uni well oiled, depending on were im riding I will use the appropriate one...

They both have ther place!!


foam in dirty water is bad and k+n in dusty conditions are bad,

Good point with the water soaked foam filter. It would hold a lot of water.
I only ride mx so I just deal with dust, sand and the occasional wet track.
Application is the way to go with it, depending on where and what conditions you ride in.

[slightlybent47]

So the answer to the op question would be. It depends on a lot of the factors that have been discussed.

[Wheelie]

I've been running a K&N on my 400 for nearly 10 years and have yet to see any signs of dirt/debris on the clean side of the filter. Some of the riding conditions throughout the years have been pretty harsh--I oil the filter and the outerwear.

[NacsMXer]

Originally posted by DnB_racing
if your running dusty areas I run the foam , but muddy watery areas I dont like the way the foam holds the water and chokes out the carb, and muddy dirty water will pore into the carb,

I have both the K+N with drywear outer and the Uni well oiled, depending on were im riding I will use the appropriate one...

They both have ther place!!


foam in dirty water is bad and k+n in dusty conditions are bad,

Outerwears makes one for the UNI. If you bought one for it, you wouldn't have the same issues with the filter getting soaked.

If you have the Outerwear option for your foam filter, I don't see any advantage to running the K&N. Wet conditions, put an Outerwear on it. People say sand can get into a foam filter....put an Outerwear on it problem solved. Like I said, maybe in all out drag racing or road courses where you don't need the protection of foam, but anywhere else foam protects much better.

[DnB_racing]

Originally posted by NacsMXer
Outerwears makes one for the UNI. If you bought one for it, you wouldn't have the same issues with the filter getting soaked.

If you have the Outerwear option for your foam filter, I don't see any advantage to running the K&N. Wet conditions, put an Outerwear on it. People say sand can get into a foam filter....put an Outerwear on it problem solved. Like I said, maybe in all out drag racing or road courses where you don't need the protection of foam, but anywhere else foam protects much better. the problem is that outerwears dont stop all the water only stops splashing water if you doing any water crossings, foam will get soaked and hold the water were the cotton weave will dry out immediately... dont get me wrong I like foam but not for real wet areas.. I run both types depending on riding conditions ... people that swear by either one are really missing out on full potential of the circumstances they are riding in, or only ride in the same conditions all the time, I like variety of conditions, and need both types to handle the conditions, and sometimes you have to adapt to the conditions appropriately,
but do what you feel is best,I love it when I pass peoples quads when they are too stubborn to realize that you have to keep open minds

[NacsMXer]

Originally posted by DnB_racing
the problem is that outerwears dont stop all the water only stops splashing water if you doing any water crossings, foam will get soaked and hold the water were the cotton weave will dry out immediately... dont get me wrong I like foam but not for real wet areas.. I run both types depending on riding conditions ... people that swear by either one are really missing out on full potential of the circumstances they are riding in, or only ride in the same conditions all the time, I like variety of conditions, and need both types to handle the conditions, and sometimes you have to adapt to the conditions appropriately,
but do what you feel is best,I love it when I pass peoples quads when they are too stubborn to realize that you have to keep open minds

Never done many water crossings or got my filters that soaked before, so i'll take your word on that lol. I could see how the thinner material of the K&N would "dry out" faster than a thick dual layer of foam. Still not that good to be running a wet filter though, i'd be running a full lid or EHS style lid with an Outerwears on the filter in that case.

[DnB_racing]

Originally posted by NacsMXer
Never done many water crossings or got my filters that soaked before, so i'll take your word on that lol. I could see how the thinner material of the K&N would "dry out" faster than a thick dual layer of foam. Still not that good to be running a wet filter though, i'd be running a full lid or EHS style lid with an Outerwears on the filter in that case. LOL yes Ive had to put the lid on at times... When i go on trips I bring... jets,sprockets, filters, tires,different heat plugs..... Im to old to be competitive without having the best possible setup I can ,LOL

I will change sprocket count, tire size and type, air pressure,jets. anything that will help.You'd be surprised how many people that are really better riders then you can be beat if they arnt setup properly

people are affraid to change, setup is half of competing, if I can setup better then half then my crew is doing and finishing good!!

[DirtyBirdRacing]

Im new to running a K&N filter WITH lid and no pre filter , I ride in coal fields so its fine dust, I havent had any issues with it running ( its apart right now doing a lot of cosmetic mods ) Ill will have the carb apart when i get my 2Bros slip on to jet it ill update if theres a lot of dirt in there or not.

When i did put my K&N on belive it or not i did notice a power difference, front end pulled up alot more in 2nd ( I never cleaned the foam filter when i bought it, switched to K&N with in 1 month of me getting it, so maybe it was cloged and thats why I noticed??

[DnB_racing]

Originally posted by DirtyBirdRacing
Im new to running a K&N filter WITH lid and no pre filter , I ride in coal fields so its fine dust, I havent had any issues with it running ( its apart right now doing a lot of cosmetic mods ) Ill will have the carb apart when i get my 2Bros slip on to jet it ill update if theres a lot of dirt in there or not.

When i did put my K&N on belive it or not i did notice a power difference, front end pulled up alot more in 2nd ( I never cleaned the foam filter when i bought it, switched to K&N with in 1 month of me getting it, so maybe it was cloged and thats why I noticed?? you bring up probably the most important point!!! if the filter isn't maintained and cleaned faithfully it wont matter what type you use it will clog or damage your motor and carb,,,

the best filter is a well oiled clean filter!!

[DirtyBirdRacing]

Originally posted by DnB_racing
you bring up probably the most important point!!! if the filter isn't maintained and cleaned faithfully it wont matter what type you use it will clog or damage your motor and carb,,,

the best filter is a well oiled clean filter!!

I was net to quads and didnt really know/think of what i should clean, I Clean and OIL my K&N filter now, and every time i do, Its reall dirty. I dont really understand how people say it lets stuff pass seems to be working just fine in Coal powder. Again I will post an update to how dirty the carb is when i take it apart.

[evan402]

I run a K&N just because i always have. And to be honest i have never thought one would be better than the other. I have never had an issue with dust getting thru my filter into my carb, but after reading slightlybent and Nacs posts i am going to buy an UNI. Better safe than sorry.

[slightlybent47]

Here’s the thing. I’m not apposed to using a better flowing filter. In fact I wish I could.
And I would use one in a deferent situation. I have the money for a filter and the will to keep it clean and oiled properly. I don’t have the money to keep rebuilding the motor.
The motor will only last so long as it is, why would I want to wear it out any faster?

Truth be told those same people that swear by the K&N and think that little gain in HP will win races. Will run worn tires and lose more traction then the gain there getting from the filter. I have done all kinds of mods to increase power but this is the one area where the risk is not worth the gain, for the type of riding I (we) do.

Keeping fresh rubber on the bike will give you better results and not be a risk to the motor. After all no amount of power will do you any good if you don’t get it to the ground.

With small motors and not having much HP to begin with, I agree every little bit helps.
But riding style and teqnique, body passion, the very dirt you are riding on and many other factors play a roll in how fast you can be.

[evan402]

Originally posted by slightlybent47
With small motors and not having much HP to begin with, I agree every little bit helps.
But riding style and teqnique, body passion, the very dirt you are riding on and many other factors play a roll in how fast you can be.

i dont know what my body passion has to do with it, lol. But if you mean position then yes. I ride trails and tracks but for now not races so. Yes i am more concerned with the life of my motor over the slight gain the filter would do.

[kbnorth99]

Originally posted by slightlybent47

Truth be told those same people that swear by the K&N and think that little gain in HP will win races. Will run worn tires and lose more traction then the gain there getting from the filter.

Where as I respect your opinion regarding the filters, this comment is not warranted. Just because I have a different view that you do does not make me less intelligent. For the record I do like the difference in the K&N vs stock and... NO I DON'T ride on worn tires.

Your argument that the gain is not worth the risk is of course based on the assumption that the K&N is an increased risk to the motor. Please keep in mind that that is your opinion. Yours and many others but still your opinion is no better or worse than the opinion of me and the other people who feel the same. My experience in a couple short years in of atv's but a lifetime of farming and offroading tells me that the K&N's when used properly work great. Yours tells you something different. Until someone conducts some type of testing that provides proof one way or the other then they are just still our opinions.

Let's keep the the discussion clean and save the insults for a different time. After all we are all friends here right?

[slightlybent47]

Originally posted by kbnorth99
Where as I respect your opinion regarding the filters, this comment is not warranted. Just because I have a different view that you do does not make me less intelligent. For the record I do like the difference in the K&N vs stock and... NO I DON'T ride on worn tires.

Your argument that the gain is not worth the risk is of course based on the assumption that the K&N is an increased risk to the motor. Please keep in mind that that is your opinion. Yours and many others but still your opinion is no better or worse than the opinion of me and the other people who feel the same. My experience in a couple short years in of atv's but a lifetime of farming and offroading tells me that the K&N's when used properly work great. Yours tells you something different. Until someone conducts some type of testing that provides proof one way or the other then they are just still our opinions.

Let's keep the the discussion clean and save the insults for a different time. After all we are all friends here right?


Well sr. if you are one of the intelligent ones that already know this then I was not talking to you. Did I quote you or point you out? NO I did not.
I was making a general statement so those that had not thought about there tires might do so.
As for testing there have been several people that have spent the money to do dyno test that prove that K&N filter do flow better.
And the people at K&N do research of there own to improve the flow of there filters.
No where in any add does K&N say there filter traps dirt and dust better then a foam filter. They only say it flows better, not filter better.
There is a big deference in air flow and the ability to trap small dust and dirt.

If K&N works for you then be my guest and run what you want. You have your opinion and I have mine.
But don’t say I called you out or was referring to you specifically. If you are that paranoid to think so then you must have doubts about K&N as well.lol

[kbnorth99]

Originally posted by slightlybent47
Well sr. if you are one of the intelligent ones that already know this then I was not talking to you. Did I quote you or point you out? NO I did not.
I was making a general statement so those that had not thought about there tires might do so.
As for testing there have been several people that have spent the money to do dyno test that prove that K&N filter do flow better.
And the people at K&N do research of there own to improve the flow of there filters.
No where in any add does K&N say there filter traps dirt and dust better then a foam filter. They only say it flows better, not filter better.
There is a big deference in air flow and the ability to trap small dust and dirt.

If K&N works for you then be my guest and run what you want. You have your opinion and I have mine.
But don’t say I called you out or was referring to you specifically. If you are that paranoid to think so then you must have doubts about K&N as well.lol

I'm not paranoid and I'm not trying to start an argument. I just wanted to point out that your post came across as offensive. Our opinions differ which is no big deal but it sounded like you were saying that all the people who have the opposing opinion are too dumb to know some basic concepts of riding. That's all. I quoted a post because that was the specific post that I felt was a little off.

It doesn't matter what anyone runs or why. I'm just pointing out that your post could have been worded differently. If my post should have been worded differently, then I apologize. No harm, no foul. I don't wanna derail the thread anymore.

[slightlybent47]

Here’s the thing. I’m not apposed to using a better flowing filter. In fact I wish I could.
And I would use one in a deferent situation. I have the money for a filter and the will to keep it clean and oiled properly. I don’t have the money to keep rebuilding the motor.
The motor will only last so long as it is, why would I want to wear it out any faster?

Truth be told (some of) those same people that swear by the K&N and think that little gain in HP will win races. Will run worn tires and lose more traction then the gain there getting from the filter. I have done all kinds of mods to increase power but this is the one area where the risk is not worth the gain, for the type of riding I (we) do.

Keeping fresh rubber on the bike will give you better results and not be a risk to the motor. After all no amount of power will do you any good if you don’t get it to the ground.

With small motors and not having much HP to begin with, I agree every little bit helps.
But riding style and teqnique, body passion, the very dirt you are riding on and many other factors play a roll in how fast you can be.

There I added (Some of) to the post. Now does that make you feel better?
I guess the way it was worded it sounded like I was referring to all. My bad!

[CJM]

Lets fight nice now, ok?

People can run whatever filter they want truth be told, I dont give a damn really. I only suggest a foam filter is better b/c it does indeed filter better than a paper filter since the holes are much smaller in a foam one.

However run whatever filter you damn wish, this goes out to anyone and everyone who likes one of the other or wants to argue their point.

[slightlybent47]

Sorry man I was feeling a bit confrontational earlier.