I USED to use K&N filters on my dirt bikes and quads. Until I found dust in the inlet boots (carb side of filter). After that went to UNIs, no more dust in the boots. We are talking a lot dustier environment than our bikes will ever see, but over time??? Just my .02.

Rest In Peace Justin Randol (1989-2008) Ride like the wind Son.
http://s282.photobucket.com/albums/kk266/BlackStar_1961/Justin/
http://www.youtube.com/watch?v=S8OvOPlEaKE
2005 Midnight Warrior
2007 Yamaha FZ1
2008 Yamaha FJR1300
1978 Suzuki GS1000
http://s282.photobucket.com/albums/kk266/BlackStar_1961/