K&N RK-3931 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     3 Customer Reviews
$154.99 USD
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Product Overview

  • Designed to increase horsepower & torque
  • Dyno-tuned velocity stack
  • Excellent Air Filtration
  • Washable and reusable lifetime air filter
  • Not legal for highway use in states adopting California emission regulations
The K&N RK-3931 Intake System-Harley Davidson fits some Harley Davidson FLD Switchback, Harley Davidson FXD Dyna Super Glide, Harley Davidson FXDB Street Bob, Harley Davidson FXDC Super Glide Custom, Harley Davidson FXDF Fat Bob, Harley Davidson FXDL Dyna Low Rider, and Harley Davidson FXDWG Dyna Wide Glide models. See vehicle applications link for details.
K&N Air Cleaner Assemblies are designed to get more horsepower from your Harley-Davidson® motorcycle. These air cleaner assemblies replace the stock air filter and backplate with an oversized K&N Air Filter and custom aluminum backing plate. These assemblies utilizes the stock cover to maintain stock appearance.

[More Information on High-Flow Air Intake Systems for Harley-Davidson Motorcycles]
Estimated Horsepower Gain6.54 HP @ 5100 RPM
Replacement FilterE-3975
Air Filter ColorRed
Air Filter MaterialCotton Gauze
Warranty1,000,000 Miles/10 Year
Product StyleMotorcycle Intake System
Size9 Inch
Air Filter ShapeUnique
Air Filter Height2.125 in (54 mm)
Air Filter Outlet ShapeNot Flanged
CARB EO NumberD-269-59
Street Legal In All US StatesYes
TUV Approved (Europe)No
Inlet Diameter2.406 in (61 mm)
Overall Height2.5 in (64 mm)
Top StyleMetal
Top MaterialAluminum
Clamps IncludedNo Clamps Included
Clamp StyleNo Clamps Required
Clamp MaterialNo Clamps Required
Weight3.1 lb (1.4 kg)
Product Box Height4.88 in (124 mm)
Product Box Length11.75 in (298 mm)
Product Box Width9.5 in (241 mm)
Couplers IncludedNone
Mounting Hardware IncludedYes
Neck Flange2.406 in (61 mm)
Horsepower gains based on similar vehicle dynamometer test. Results will vary.
WARNING: Cancer and reproductive

K&N RK-3931 Intake System-Harley Davidson Product Reviews

Wednesday, March 6, 2019 - Part RK-3931
What can I say? I have been using K&N filters on all my vehicles for decades now and am extremely happy with their products. This particular air filter is one of my favorites. Not only does my bike appear nearly stock, but the hidden velocity stack is exactly what I want. Easy installation and great performance. Perfect.

William Carling
Moreno Valley, California
Saturday, August 26, 2017 - Part RK-3931
If you are thinking about getting one, do it. Has completely awakened my now 2 year old bike.

San Diego, California
Tuesday, June 6, 2017 - Part RK-3931
Was easy to install. I actually felt a difference in performance. The louder sound coming from the filter/intake area is really cool. If fact my wife said, "what is that sound coming from the engine?" as she grabbed my jacket to hold on tighter. :o I like the original Harley-D cover application (making it a sleeper look). Thanks.

D Worrell
Seattle, Washington