K&N air filter:mx xtreme

[That YZ450F Guy]

Does anyone know rufly how much of a horse power gain i would get switching from a stock air filter to a Mx Xtreme K&N air filter??

[racerx_217]

not much, maybe a few tenths of a hp

[Slackkinhard]

Zzzzzzero!

[downonmonday]

Very little gain, but re-jetting would be a must. Unless your bike is fuel injected?

[J_Daniels]

The main thing about K&N (and all other wet-gauze filters) is that they pass fine dust into the engine. Not a big deal on street applications, I have one on my truck and streetbike. When you pull the filter off, there really is a bit of dust in the intake tract.

They are used often in endurance off road racing like Baja because they take longer to pack up and plug than paper or foam. I wouldn't use on on my dirt bike, though- foam is the way to go.

[juliend]

Exactly. You'll gain nothing but some extra wear on the engine components.

[mikewrf18]

The main thing about K&N (and all other wet-gauze filters) is that they pass fine dust into the engine. Not a big deal on street applications, I have one on my truck and streetbike. When you pull the filter off, there really is a bit of dust in the intake tract.

They are used often in endurance off road racing like Baja because they take longer to pack up and plug than paper or foam. I wouldn't use on on my dirt bike, though- foam is the way to go.

Without starting another KandN versus Foam filter debate I concure with this.^^^^^ There is probably hours of reading material on this site debating this topic.

I would run a KandN for street applications and nothing more. If you're set on a KandN, I'd run a pre filter, but then again wouldn't that defeat the purpose?

[Mike38]

My nephew that races at the Pro level claims 2.5 horse power increase from a stock 2011 CRF450R. Done on a dyno, by a impartial party. All he did was install a K&N filter and set the fuel injection accordingly for the higher air flow.

K&N filters do not allow any more dirt pass threw them then any other air filter, as long as they are properly maintained. Rinsing a K&N in pre mix thinking you cleaned and oiled the filter all in one shot, is not proper maintenance. You must use a K&N recharge kit.

Mater of fact, a properly maintained K&N filter will stop dirt particles that are smaller then dirt found naturally in gasoline. There is a certain amount of “dirt” found in gasoline. Better grades of gas, have less and smaller “dirt” particles, but a certain amount is always there. If memory serves me, it is common to find dirt particles in fuel that measure 3 to 4 microns in diameter. A properly maintained K&N filter will stop particles as small as 2.5 microns. Therefore, the gas you are using is doing more damage to your engine then the K&N filter is.

Pro Flattrack racers, at the GNC level all use open K&N filters on their twins (Harley XR750 for the most part.) A Harley XR750 engine costs right around $12,000 to buy, and then you have to build it because it comes as a parts kit. Do you honestly think someone would spend that kind of money on a motorcycle engine, and all the labor involved assembling it, then run a junk air filter?

I do not work for K&N. I do not sell K&N products. I have been using them successfully for over 35 years now.

[Slackkinhard]

Do any of the factory teams use them?

[downonmonday]

Do any of the factory teams use them?

I see stickers on several Pro bikes, but I'm not sure what is under the seat though??

I did use a K&N when I had my RMZ250. I could tell the bike was breathing more freely and I had to rejet. I did notice dust in the intake boot, but no dust if I used a foam filter. I did clean and oil the K&N with their product...hell, I probably over oiled the K&N. ? I do use K&N cold air intake in my Dodge 1500 and my GSXR 750. No traces of dust/dirt.

[yzdaddy]

the oldest 2 race bikes i own with k&n filters are 1974 models 250&360 they still have original K&n s from 74 and their still good. neither bike has never had crank problems or top end problems other than normal wear. all the bikes i own street and dirt have k&ns like mike38 says you have to use recharge kits and clean them when there dirty. i have never noticed any dirt in intakes.

[J_Daniels]

K&N filters do not allow any more dirt pass threw them then any other air filter, as long as they are properly maintained.

This is patently untrue and has been proven time and again in impartial testing. Paper filters best, then foam, then wet gauze. You can pull up your own examples, it's all over the web.

Rinsing a K&N in pre mix thinking you cleaned and oiled the filter all in one shot, is not proper maintenance. You must use a K&N recharge kit.

I think it's a given that no one should clean a K&N with anything other than the manufacturer's kit; I know I don't. In fact, a clean gauze or paper filter passes more and larger dirt particles than a dirty one. Overcleaning a K&N is detrimental to it's fltering capabilties.

You are fighting a losing battle to say that K&N is a perfect filter. Thousands of guys like me have used them and seen dust in the intake tract. I'm not saying that they are junk, just that they have a proper place as a racing or street filter. They do make more power, sometimes significantly more depending on how restrictive the stock filter is on a specific machine. BUT on a dirtbike in dusty conditions, foam protects better.

[m320]

Do your own test I did........I'll stick with the K&N the foam let dust through.....

[Mx250Rider22]

Lolz, this post is ridiculous. It comes down to personal preference and knowing how to properly clean and oil your filter. I generally see dirtier intakes when people use k&n and will always use foam, it comes stock for a reason.

[Coviello]

And it bothers me the most when people say they can go 4x as long without cleaning the k&n over the foam. Well duh. Do you magically think there is less dust in the air than before. No. All that means is that the filter isnt catching as much crap that is going straight into the engine. More airflow yes. With more airflow means that there is more room in that filter for air to pass through which also means more room for dirt to pass through. Whoever says k&n adds horsepower is correct. Whoever says it protect more is so far from wrong its not even funny.

[mikewrf18]

I had a feeling this thread would turn into a filter debate!?

To each his own. When I first started riding I purchased a K and N for my yzf. Never received any damage to the bike to my knowledge, but I also used a filter skin often. I feel safer using foam now though.

[Slackkinhard]

your air filter is not the HP restrictor in the system...solely changing it won't affect HP

[mkeeping]

your air filter is not the HP restrictor in the system...solely changing it won't affect HP

That is not true:

https://www.thumpertalk.com/forum/showthread.php?t=695435

You can see when he removed the filter completely there were HP gains.

[J_Daniels]

All that means is that the filter isnt catching as much crap that is going straight into the engine.

Actually it's the opposite with paper and wet gauze filters. Dirt takes up space in the matrix and they filter better as they get dirtier. Of course this means they are also more restrictive as well.

It IS true with a foam filter; as dirt adheres to and covers the oil in the foam, it allows new dirt particles to 'bounce' their way in.

[Slackkinhard]

That is not true:

https://www.thumpertalk.com/forum/showthread.php?t=695435

You can see when he removed the filter completely there were HP gains.

Closed circuit tests...gotta love em. Where did he test replacing the stock filter with a K&N? And where did he show that in real world use, that over the duration of a filter application that HP increased? All I see is that he removed everything and ran the test. Good way to get a MAX type reading, but hard to get a MIN, an AVG or a Std Deviation. So, hard to use that test as proof of replacing your foam with fiber.