Harley-Davidson Twin Cam Enthusiasts Recommend K&N Air Filter Assembly

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K&N's popular custom air filter assembly, part RK-3909-1, was designed to provide better performance while retaining the stock appearance of 1999-2007 Twin Cam® Harley-Davidson® engines (see applications).  It comes with a powder coated billet aluminum back plate that eliminates external breathers and features a built-in, dyno-tuned velocity stack.  The resulting design provides significant airflow increase to the engine without sacrificing filtration.  This product has generated a lot of excitement from Harley-Davidson motorcycle owners. 

Brian Keller of Boston, Massachusetts has a 2005 Harley Davidson Road King Classic with 27,500 miles. He also has a K&N Engineering Air Filter Assembly (RK-3909-1).

Brian Keller's 2005 Harley Davidson Road King Classic
Brian Keller's 2005 Harley Davidson Road King Classic

K&N Engineering's RK-3909-1
K&N Engineering's RK-3909-1
“K&N makes a terrific product,” said Keller. “After adding Bassani True-Dual Powercurve pipes with Reverse Cone Megaphone slip-ons, a Dynojet power commander and the K&N High Flow Air Filter, I gained some serious horsepower and torque.”

Brian Keller said K&N adds horsepower and torque to his Harley
Brian Keller said K&N adds horsepower and torque to his Harley
Keller said having a motorcycle can be all about power and torque, but safety is also important. “When I get on the highway I have the throttle I need,” he said. “The bike has instant power with a little twist.”

One of the reasons Keller bought his Twin Cam Harley Davidson was for long distance riding. “It’s super smooth and I can go 400 miles in comfort,” he said. “I recommend RK-3909-1 to everyone I ride with. When I added the K&N Air Filter it was a smooth ride all the time. It is like night and day with the K&N Air Filter. My Harley runs like it’s brand new.”

“Wizard Cycles of Nashua, New Hampshire installed the K&N Air Filter Assembly and pipes for me,” said Keller. “Speeds Performance Plus of Elk River, Minnesota installed my Power Commander and I dyno-tuned my bike at Laconia Bike Week this year. K&N gives me the extra juice I need and allows me to keep up with the Screaming Eagle Harley engines.  It’s also about having a good time, knowing I have a fantastic K&N Air Filter."

Kenneth Roberg of Franklin Park, Illinois also installed K&N’s RK-3909-1. “At the same time I installed a new exhaust system and a fuel pack which coordinates the right fuel mix with my setup,” said Roberg. “For the most part I am satisfied and have noticed better fuel mileage. By the way, the K&N Filter fits behind the stock cover perfectly.”

Paul Haberstroh is a professional photographer in Lafayette, Colorado. He knows film and he knows K&N Filters. Haberstroh also drives a 2007 Harley Davidson Road King Classic around his beautiful small town.

Paul Haberstroh uses K&N Products, phot by Paul Haberstroh
Paul Haberstroh uses K&N Products, photo by Paul Haberstroh
Paul Haberstorh gets improved throttle response with K&N, photo by Paul Haberstroh
Paul Haberstroh gets improved throttle response with K&N, photo by Paul Haberstroh
“I’ve used K&N Air Filters for as long as I can remember and I’ve had a camera in my hand for as long as I remember,” said the 49-year-old. “I used to ride a BMW, but I went to Harley when they came out with the Twin-Cam engine and the retro classic styling.”
Paul Haberstroh noticed an improvement in gas milage with K&N, photo by Paul Haberstroh
Paul Haberstroh noticed an improvement in gas mileage with K&N, photo by Paul Haberstroh

Haberstroh equipped his Harley with K&N Engineering’s RK-3909-1.  “I really noticed a difference in the throttle,” said Haberstroh. “K&N also improved my acceleration. It’s amazing how good the gas mileage is with K&N on my Harley. This is a very comfortable machine. I can go hundreds of miles on it and gas mileage is important.”

The Colorado wedding photographer also drives a 2007 Dodge Ram 1500 pick up.  “I put a K&N 63-Series AirCharger Air Intake on my Dodge,” he said. “I live at 6000 feet and my work frequently takes me up to 10,000 feet in elevation. Normally I’d lose performance, but with K&N I never have to worry about that.  My Dodge works well in the thin air with K&N. It really makes a difference in performance for people like me who live in the higher elevations.”

Haberstroh quit his day job ten years ago to start Distinctive Imaging, Inc., in Colorado. He took his camera and he took his commitment to K&N.

Find K&N products for your vehicle using the K&N application search then use the K&N dealer search to find a K&N dealer in your part of the world.

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K&N Engineering, Inc., with headquarters in Riverside, California, has been the world's leader in performance filter technology since 1969, serving the needs of the automotive, motorcycle, marine, industrial and military markets. K&N is heavily involved in nearly every form of motorsports from off-road and powersports to drag racing, stock cars and road racing. For more information about K&N Filters, please contact K&N Engineering, Inc., P.O. Box 1329, Riverside, CA 92502-1329, (800) 213-4182 for a dealer near you, (800) 858-3333 for technical service/questions, (951) 826-4001 Fax, e-mail, or visit