Originally I put this on my CBR600F4 as part of my yearly maintenance. When I took the bike out in spring it ran like shit. Living in Wisconsin, I figured the carbs were messed up from sitting all winter. So I spent $80 and a week rebuilding the carbs. That wasn't the issue. On a whim took the brand new filter off and it ran like a champ. So needless to say I was pretty pissed. I emailed bikemaster on a Sunday night and on Tuesday i got a package from them with a new filter (that actually worked) and free cleaner and oil. They even payed my shipping to send the new one back.