[2015 Z Force 800 53/Trail EPS]

This short shows two of the three reasons we do not recommend a K&N air filter on any machine. Note both oil and dirt on the sensor
https://www.facebook.com/share/r/16apEvgBCB/
And when you use a Unifilter you must oil it correctly, then roll-up a paper towel inside to sop-up the access, then let dry for two hours before pulling air through it to avoid getting any treatment pulled in.  And always use a quality foam filter treatment. like Maxima FFT or Fab-1, or Bel-Ray