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K&N's RK Series was developed to get more horsepower from your Twin Cam Harley-Davidson engine. Built around the legendary K&N High-Flow Air Filter, the this RK Series assembly includes an innovative powder coated billet aluminum back plate that eliminates external breathers and features a built-in, dyno-tuned velocity stack. The result is a significant airflow increase to the engine without sacrificing filtration. This RK Series assembly retains a factory appearance by utilizing the stock air cleaner cover. The RK-3910-1 comes with a larger air filter and longer spacers than the RK-3909-1.
Designed to increase horsepower & torque
Dyno-tuned velocity stack
Washable and reusable
Excellent air filtration
Estimated Horsepower Gain
6.05 HP @ 5206 RPM
Replacement Filter
E-3972
Air Filter Color
Red
Air Filter Material
Cotton Gauze
Warranty
No-Hassle Lifetime Limited
Product Style
Motorcycle Intake System
Size
7 Inch
Air Filter Shape
Round
Air Filter Height
1.625 in (41 mm)
Air Filter Inside Diameter
6.188 in (157 mm)
Air Filter Outlet Shape
Not Flanged
CARB EO Number
D-269-35/55
Street Legal In All US States
Not legal for sale or use in California on any pollution controlled motor vehicle. NOTE: Some specific models and years may be legal in CA. Check the CARB status on your vehicle in the applications listings.
