Is it worth the money to install a k&n air filter, is it actually noticeable

 

You'll notice your midrange is gone and over time you'll notice your valve seats are eaten up.

Not worth it.These bikes run best with paper filters and last longer with OEM oil filters.

 

I've done some carb tuning with the paper filter and a custom exhaust and would not want to try the cotton gauze hi-flow filters. I have heard that they aren't as good for the heads of these motors as the paper ones are.

Kjohnson seems to have quite a bit of experience with racing and such so his experience with this is firsthand.

 

I've been running a K&N for about 10 years now. With as many miles that I put on, I would be going through about 3 to 4 paper filter ($45 a pop) a year and I can't afford it when compounded with oil changes. My K&N paid for itself in two cleanings and I've probably cleaned that thing a hundred times at least by now. I have heard that the BMC filters are much better than the K&N but I can't confirm this. I've been thinking of researching into this a little though.
When I first put the K&N in, it leaned the mixture. To fix that, all I had to do was shim the needles. When I added the slip on, the mixture severely leaned out. With some tuning, problem solved. I had to fatten up the pilot, bumped up the main, and additional shims to the needles. Been running great ever since. I've got a nice tan color on the plugs.
Granted... I'm not racing and so my bike isn't under those extreme race conditions. But on the street, a K&N has worked well for me.