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K&N Custom Air Filter Assembly for Various Harley Davidson Motorcycles - RK-3909-1

K&N Custom Air Filter Assembly for Various Harley Davidson Motorcycles - RK-3909-1

K&N Air Filter RK-3909-1 - Single



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  • Description
  • Benefits
  • Technical Info
  • Shipping Explained

K&N Custom Air Filter Assembly for Various Harley Davidson Motorcycles - RK-3909-1

General Details:

Version1-5/8" Tall Filter

Addtional Images:

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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 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. The RK-3910-1 comes with a larger air filter and longer spacers than the RK-3909-1.


K&N's Aircharger® Performance Intake Kit will get more horsepower from your Harley-Davidson® motorcycle. K&N's air intake for Touring Models gained an estimated 12.9 horsepower at the rear wheel and K&N's air intake for Softail Models gained an estimated 10.2 horsepower. This high flow Intake System increases power by eliminating the restrictive stock OE air cleaner and replacing it with a K&N high flow air filter and mandrel bent aluminum intake tube. This complete intake system will help relieve the labored feeling associated with two-up riding or loaded touring. K&N's high flow intake system gives your Harley-Davidson an aggressive appearance while providing a significant increase in airflow resulting in more power.

  • Guaranteed Increase in Horsepower
  • Aggressive appearance while providing outstanding airflow
  • Completely replaces stock air cleaner assembly
  • Washable, K&N high flow air filter equals longer life
  • Custom aluminum throttle body mounting plate
  • Includes complete breather assembly and mounting hardware
  • High flow mandrel bent aluminum intake tube
  • Available in textured black or bright mirror finishes
  • K&N Drycharger® available for extended service intervals
  • Includes K&N Million Mile Limited Warranty®

Technical Information:

K&N Part RK-3909-1 Product Specifications

  • Product Style: Motorcycle Intake System
  • Estimated Horsepower Gain: 6.05 HP @ 5206 RPM
  • Street Legal In All US States: See Application Link Below
  • TUV Approved (Europe): No
  • Air Filter Shape: Round
  • Color: Red
  • Filter Height: 1.625 in (41 mm)
  • Neck Flange: 2.25 in (57 mm)
  • Overall Height: 1.688 in (43 mm)
  • Replacement Filter: E-3972
  • Size: 7 Inch
  • Style: Oval
  • Top Material/Finish: Black Powder Coated
  • Top Style: Metal
  • Weight: 3.3 lb (1.5 kg)


SHIPPING IS FREE* for orders of £75 and over , regardless of the weight of your order.
We've tried to keep all other shipping costs as low as we can.

Carriage starts at just £0.95 (inc VAT) for small items, with our most common courier rate set at £4.99 for orders of 5kg (enough for 5 litres of oil).

  • *Free shipping is available for UK Royal Mail, UPS Access Point™ (click & collect) and standard UK courier services (not express / priority / islands).
  • Courier surcharges mean we are unable to offer free "to the door" courier shipping from us in Cornwall up to Highlands / Grampian in Scotland - and because we send a lot of liquids, not every courier option is available to us. UPS Access Point™ (click & collect) is available as a free shipping option across Scotland, Wales and England, wherever there is a UPS Access Point™ Location.
  • Carriage charges are based on weight - please see our table of carriage costs for full details (although adding an item to your cart and viewing the calculated carriage is often easier!).
  • Priority shipping is also available.

How long will it take to get my order?

We give an estimate of delivery dates as you shop and in your basket. The vast majority of items are held in stock and dispatched from our UK warehouse and we'll do all we can to get your order to you as quickly as possible.

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