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K&N RK-3947B Intake System-Harley Davidson

Custom Assemblies > Intake System-Harley Davidson
Rating Star 1 Rating Star 2 Rating Star 3 Rating Star 4 Rating Star 5   4.0 out of 5 stars   2 Customer Reviews
  • Guaranteed increase in horsepower
  • Replaces the stock air filter and cleaner backing plate assembly
  • Washable, oversized K&N high-flow air filter for long service interval
  • Oversized black, powder coated aluminum backing plate provides solid mounting
  • Dyno tuned velocity stack directs airflow to engine
  • Built in breathers replace external OE breathers
  • Includes K&N Million Mile Limited Warranty
The K&N RK-3947B Intake System-Harley Davidson fits some Harley Davidson FLHP Road King Police, Harley Davidson FLHR Road King, Harley Davidson FLHRC Road King Classic, Harley Davidson FLHT Electra Glide Standard, Harley Davidson FLHTC Electra Glide Classic, Harley Davidson FLHTCU Electra Glide Ultra Classic, Harley Davidson FLHTCU Ultra Classic Electra Glide, Harley Davidson FLHTCUL Electra Glide Ultra Classic Low, Harley Davidson FLHTCUTG Tri Glide Ultra, Harley Davidson FLHTCUTG Tri Glide Ultra Classic, Harley Davidson FLHTK Electra Glide Ultra Limited, Harley Davidson FLHTK Ultra Limited, Harley Davidson FLHTKL Ultra Limited Low, Harley Davidson FLHTP Electra Glide Police, Harley Davidson FLHX Street Glide, Harley Davidson FLHXS Street Glide Special, Harley Davidson FLHXXX Street Glide Trike, Harley Davidson FLRT Freewheeler, Harley Davidson FLTR Road Glide, Harley Davidson FLTRU Road Glide Ultra, Harley Davidson FLTRX Road Glide, Harley Davidson FLTRX Road Glide Custom, and Harley Davidson FLTRXS Road Glide Special models. See vehicle applications link for details.
The K&N RK-3947B High-Flow Air Intake System increases engine intake airflow and delivers more horsepower & torque to many Harley-Davidson FLT and FLH model motorcycles. The intake system increases power by eliminating the stock OE air cleaner and replacing it with a complete High-Flow Air Intake System. The intake system comes with a K&N air filter for high air flow and long service intervals. The K&N high-flow air filter is washable, reusable, pre-oiled and ready for installation.

[RK Series Street Metal High Flow Air Intakes for Harley-Davidson Motorcycles]

Product Specifications

Estimated Horsepower Gain7.43 HP @ 4786 RPM
Replacement FilterE-3975
Air Filter ColorRed
Air Filter MaterialCotton Gauze
Product StyleMotorcycle Intake System
Air Filter Height2.125 in (54 mm)
Street Legal In All US States No
TUV Approved (Europe)No
Overall Height2.125 in (54 mm)
Top MaterialBlack Powder Coated
Package Quantity1
Weight4.3 lb (2 kg)
Product Box Height4.88 in (124 mm)
Product Box Length11.75 in (298 mm)
Product Box Width9.5 in (241 mm)
California RestrictedNot legal for sale or use in California
Mounting Hardware IncludedYes
Horsepower gains based on similar vehicle dynamometer test. Results will vary.

K&N RK-3947B Intake System-Harley Davidson Product Reviews

Thursday, March 1, 2018 - Part RK-3947B
I recently purchased the RK-3947B for my 2009 Harley Electraglide. K&Ns website was easy to navigate, shipping was fast, I did have a small hick-up with just the filter but yet again K&N pulled through and sent a replacement. I am 100 satisfied with the product and their support. Thank you K&N.

Michael Vandewalker
Johnstown, New York
Sunday, March 26, 2017 - Part RK-3947B
I have used K&N filters since the 70s and highly recommend them. I am, however, disappointed that there is no dry charger wrap for the RK-3947B. You would think they would be available for all motorcycle intake systems.

Brad W.
St Louis, Missouri