It is common practice in many amateur-built engine installations, from Rotaxes to Lycomings, to use K&N filters. They do a wonderful job of filtering the air, and they are reusable. However, they only are able to perform correctly if they are properly cared for. They should be cleaned annually at a minimum with K&N filter cleaner and then lightly oiled with K&N filter oil. Without the oil, which leaves a slight pink color on the filter, they will not filter properly. The one in the photo above was not oiled.
In Case You Missed it
Give Me a Brake
When his Zenith CH 701 wouldn't stay put during runup and tended to roll on an incline, builder Chuck Deiterich came up with a do-it-yourself solution.
Ask the DAR
Mel Asberry - 0
When do service bulletins have the force of law with regard to Experimental/Amateur-Builts?