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 backplate 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.
- Guaranteed increase in horsepower and torque.
- Replaces the stock air filter and cleaner backing plate assembly.
- Fits behind the O.E. air cleaner cover maintaining the factory appearance.
- Washable, oversized K&N high-flow air filter equals longer life.
- Oversized black, powder coated aluminum backing plate provides solid mounting.
- Dyno tuned velocity stack directs airflow to engine.
- Built-in breathers replace external O.E. breathers (where applicable).
- Washable and reusable.
- Excellent air filtration.
- Includes K&N Million Mile Limited Warranty.
Detailed Specifications:
- K&N part number: RK-3909-1.
- Estimated horsepower gain: 6.05 HP @ 5206 RPM.
- Air filter color: Red.
- Air filter height: 1.625 inches (41 mm).
- Air filter inside diameter: 6.188 inches (157 mm).
- Air filter material: Cotton gauze.
- Air filter outlet shape: Not flanged.
- Air filter shape: Round.
- Clamp material: No clamps required.
- Clamp style: No clamps required.
- Clamps included: No.
- Color: Red.
- Filter material: Cotton gauze.
- Inlet diameter: 2.25 inches (57 mm).
- Mounting hardware included: Yes.
- Neck flange: 2.25 inches (57 mm).
- Overall height: 1.688 inches (43 mm).
- Product style: Motorcycle intake system.
- Replacement filter: E-3972.
- Size: 7 inches.
- Street legal in all US states: Based on fitment.
- Style: Oval.
- Top material / finish: Black powder coated.
- Top style: Metal.
- TUV approved (Europe): No.
- Weight: 3.3 pounds (1.5 kg).
- Note: Use with stock cleaner cover. Horsepower gains based on similar vehicle dynamometer test. Results will vary.
