This test confirms my feeling about K&N. My son got one for his XR400 and after one ride found dust in the carburetor throat. At the time we though maybe it was not sealing correctly, but I never felt comfortable with that diagnosis. Bottom line he went back to a dual stage UNI. I still use the OEM dual stage, but they are basically the same thing. The key to these filters on dirt bikes is using the correct oil. Do not use motor oil. Although it will work, proper filter oil will work much better. Real filter oil is sticky. If you put some between your thumb and finger and pull them apart, you will see thin spider webs of sticky oil connecting them. This sticky stuff really collects the dirt in dusty conditions. It also means you need to do very regular cleaning. I'm thinking regular changing of paper filters on the FJR should be good.