I bought a K & N Air Filter for my 400ex (which ran totally fine with the stock foam air filter). After installing the filter and going for a test run, I noticed that the 400ex had much more "pep" then with the foam air filter. It had better responsiveness and power. The front wheels came off the ground easier than before too.

I'm sold on the K&N. Two thumbs up!

 

thanks i was still thinking on wut air filter to go with but i think k&n im goin with.

 

lol

uni works better. The only data I have seen where a K@n was better was from a K@n dealer that did the tests themselves and they didn't even oil the uni. lmao

 

It also allows more dust into your system.

 

If you take the stock metal insert and remove the fine screen it will run just as good as the K&N and not let that much dirt into the engine. that fine screen is what restricks the foam fliter not the foam. Notice that the UNI filter doesn't have the fine screen. Try your same test with a UNI and the K&N. Read the box that the K&N comes in, "will let fine dust or dirt pass".

 

E70-You didn't mention whether you did a rejet??? If you didn't, you are running lean and you risk damaging your engine!

Your testimonial isn't really worth much! It only relates to performance, and says NOTHING about the longevity of your engine (that experiment takes more time). Performance is great, but not if you have to sacrifice your engine to get it. So, go ahead and do a long term test for us. Fortunately, the only one with anything to lose here is YOU.