http://forums.cbrworld.net/forums/191734/ShowPost.aspx Kinda an interesting article. Even though the test wasnt done on a motorcycle engine it still doesnt change the air thats going thru it. Very surprising to see the leader in air filters to get shut down so bad, be nice to have a air filter that never needs to be replaced, but in the long run it causes more damage than you might think.

Well, this review took an ST1300 and did a back to back Dyno run with the OEM Honda filter and then with a K&N and they saw a 6HP increase.

http://www.motorcycledaily.com/21september04_kandnfilter.htm

Of course, the OEM filter may have been dirty, so the increase can probably be partly attributed to that...

there might be different results for different circumstances, but in your review do they test for how much dirt goes in? or is it just how much horsepower it gains? Im sure you can probably gain horsepower with one of these filters because of how much more air it allows in, but the amount of dirt per amount of air is rediculous. The motor would gradually more dirty, things will have to be replaced sooner than they should. All in all i dont think its worth it

I had my bike recently dyno'd with a new K&N filter. I just put the original OEM filter back in and I am going to have them re-dyno it on Friday at the same shop. I will post my results this weekend.

I spent some time reading various articles, and several of them did say that modern Honda's see very little gains from the K&N and that they can actually hurt performance. Something about how well Honda designs the OEM filter and airbox, and that the K&N lets in more air and can create turbulence that can result in a loss of power. My last dyno run was only 3 weeks ago, and the OEM filter is clean, only had like 500 miles on it, so it should be a good comparison.

i never said it would not give you horsepower, it quite possibly could, but the thing im trying to explain is that the filter as a whole is bad for the motor. It allows more air than usual filters but as a result more dirt comes in with it. I would much rather have a cleaner motor than adding 2 HP that i may not even feel.

I understand that, but other sources are claiming that the K&N does not really add performance, it might even take it away, and so I am going to find out on Friday when they Dyno it.

Ive ran K&N filters on all my machines from dirtbikes and four wheelers to my f4i. Never seen any problems, even from my race quad which is always in dusty conditions. Ive seen some pretty noticeable gains with no dirt in motor. Have nothing but good experiences with K&N.

dont really know what to think now. i've always been against K&N just for the sake of a K&N.
if you're also replacing an exhaust i see the purpose but as far as the extra dirt that come with extra air flow i dont see it ruining K&N's rep. too many satisfied customers that havent reported anything bad. and it could just be a fluke/weighted test.

I agree. I ran a K&N in my 32 ford and everytime I did a rebuild the engine was filled with debris. A nice cheep 10 dollar airfilter trapped more particles, I did have to replace and clean more often, and on my engine rebuilds I did not have nearly as much debris in there.

Ive rebuilt motors on a couple race quads and seen no debris. I do clean and re-oil it often though. Maybe thats why ive had good experience...recharger kits for the K&N are like only 12 bucks.

i guess it might actually depend on the motor, i then would have to assume that the bigger the motor the more air that needs to be pulled in. My buddy has some race cars, dragters and things like that and he has told me that they never really like K&N because they had to clean the motor more than they should. They never were disappointed with any power decreases, cause in fact im sure it gave them more power. But the principle of it is that the bigger the motor the more air being sucked in. On a motorcycle, or ATV's, or dirtbikes, all of the smaller motor vehicles probably dont have big enough air intake abilities to suck in alot of dirt. The dirt comes with the air, thats common sense, but if something doesnt pull in as much air then obviously there is going to be less dirt. That might be why people with smaller motor vehicles dont notice a difference with K&N. All in all we may never know how these filters affects our motors, but i guess it all comes down to personal preference, and whether or not you actually believe its good or bad for your motor.