Vehicle Search
Search by Keyword
Search by Part
RK-3909-1 Image

K&N RK-3909-1

Custom Assemblies > Intake System-Harley Davidson
Be the first to review!

In Stock & Ready to Ship!
Free Shipping!


List Price: $268.92
Your Price: $161.99
You Save 39.8%
Qty: Find a Local Dealer

Information

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.
  • Designed to increase horsepower & torque
  • Dyno-tuned velocity stack
  • Washable and reusable
  • Excellent air filtration

Related Links

Installation Instruction Sheet
Dyno Chart - 2010 Harley Davidson Fat Boy 96ci - 9.59hp
Dyno Chart - 2006 Harley Davidson Road King 88ci - 6.05hp
News Story - Harley-Davidson Softail, Touring & Dyna Motorcycles Get Extra Power with K&N Assembly
RK-3909-1 Vehicle Applications

Part RK-3909-1 Product Specifications

Part Number: RK-3909-1 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)
Product Box Length: 11.75 in (298 mm)
Product Box Width: 9.5 in (241 mm)
Product Box Height: 4.88 in (124 mm)

Horsepower gains based on similar vehicle dynamometer test. Results will vary.

Customer Feedback

Be the first to review part RK-3909-1
Dear sirs:

All I can say is most people won't believe this but then it's their loss...in miles per gallon that is. I Own 2 Harleys, a 1979 HD Sportster that several years ago I put a K&N air filter on and felt like it doubled it's performance, and a 1999 FLSTF Fat Boy. I didn't rest there, as a year ago I put a K&N on my 2001 Dodge Ram Quad cab Cummins turbo diesel and also felt the increase in performance not to mention the scream of that turbo that I had never really heard from the factory.

Recently two of my buddies and I went on a motorcycle trip to Stecoah, N.C. Before going on the trip I changed all my fluids and serviced the whole bike. I decided to buy a K&N air filter and pitch the stock one. They were riding a 2003 Honda Goldwing, a 2005 Harley Davidson Roadking and I took my 99 Fat Boy. Prior to installing the K&N my Fat Boy got between 40 & 43 MPG. As we went from fuel stop to fuel stop my mileage was as follows: 43 MPG, 47 MPG, 46 MPG, 48 MPG and 52 MPG EVERY tank after that. My buddies only mustered 44 -46 MPG. Most people would ask what about the weight and the speed. Well both my saddle bags were packed, I had a bag with 20 lbs. on my luggage rack, plus my TBags weighed in at about 50 lbs. The weight we carried was all about the same. The motorcycle weights were different, but not enough to warrant the major difference in MPG. Also mine is carbureted and theirs are fuel injected. As far as the speeds, we were cruising on the interstate at 70 to 80 MPH through a whole fuel run which was about 200 miles. Even when I was on the tail of the dragon, which is 318 turns in 11 miles, my mileage stayed at 52 MPG. All I can say is after over 1700 miles on that trip the K&N definitely paid for itself with the increase of 9-12 MPG.

So everyone has a choice. you can pay at the pumps or spend that money on the LAST air filter you will EVER buy.
Ronnie E., Glen Rock, Pennsylvania
Since installing the K&N intake system on my 2003 Harley Davidson Fat Boy, I have noticed considerable increase in power. My Harley is the 2003 100 Year Anniversary edition and I have several anniversary parts on it, including the breather cover. With this K&N kit, I was able to maintain the use of all specialty features. The kit was very easy to install. I had it completely installed in less than 30 minutes. Thanks again and I look forward to doing more business with you in the future.
Kevin Bearden, Ocala, Florida
The technician at K&N was very quick to respond to my query and gave me excellent detailed specifications to fit an air filter to my old Harley Davidson 3 wheel golf cart. The original was lost and this filter fit perfect and performs very well and looks much better than the original. I also run K&N on my Ford Expedition.
Robert Mongeon, Pembroke, Georgia