K&N Replacement Air Filter YA-6004. For over 40 years K&N has been designing and manufacturing performance air filters for the motorcycle and ATV enthusiast interested in maximizing horsepower and acceleration. Our air filter is designed to achieve high, virtually unrestricted air flow while maintaining filtration levels critical to ensure long engine life. 1x K&N Original Air Filter YA-6004. Product Type: Air Filter. Designed to provide increased Horsepower and Acceleration. Pleated cotton media provides a large filtration area offering low restriction and long service intervals. Multi-Layers of woven cotton gauze media offers excellent filtration. Fits directly into OEM Airbox with application specific Sealing Bead ensuring a precise fit. No fuel Management modifications are normally required to obtain increased performance. Washable & reusable, most are pre-oiled and ready to ride! You can send us a message by using the “Questions and answers” section towards the bottom of the page.