The latest addition to K&N's RK Series was developed to get more horsepower from your Twin Cam Harley-Davidson engine. Provides a significant airflow increase to the engine without sacrificing filtration.
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 back plate 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
Application Summary:
| Year |
Make/Model |
| 1999-2007 |
Harley-Davidson FLHR Road King |
| 2007 |
Harley-Davidson FLHRC Road King Classic |
| 2002-2006 |
Harley-Davidson FLHRCI Road King Classic |
| 2003-2006 |
Harley-Davidson FLHRI Road King |
| 2004-2007 |
Harley-Davidson FLHRS Road King Custom |
| 2004-2006 |
Harley-Davidson FLHRSI Road King Custom |
| 1999-2007 |
Harley-Davidson FLHT Electra Glide Standard |
| 1999-2005 |
Harley-Davidson FLHTC Electra Glide Classic |
| 2007 |
Harley-Davidson FLHTC Electra Glide Classic |
| 2002-2006 |
Harley-Davidson FLHTCI Electra Glide Classic |
| 2007 |
Harley-Davidson FLHTCU Electra Glide Ultra Classic |
| 2002-2006 |
Harley-Davidson FLHTCUI Electra Glide Ultra Classic |
| 2003-2006 |
Harley-Davidson FLHTI Electra Glide Standard |
| 2006-2007 |
Harley-Davidson FLHX Street Glide |
| 2006 |
Harley-Davidson FLHXI Street Glide |
| 2006 |
Harley-Davidson FLST Heritage Softail |
| 2000-2012 |
Harley-Davidson FLSTC Heritage Softail Classic |
| 2002-2006 |
Harley-Davidson FLSTCI Heritage Softail Classic |
| 2000-2012 |
Harley-Davidson FLSTF Fat Boy |
| 2010-2012 |
Harley-Davidson FLSTFB Fat Boy Lo |
| 2001-2006 |
Harley-Davidson FLSTFI Fat Boy |
| 2006 |
Harley-Davidson FLSTI Heritage Softail |
| 2005-2012 |
Harley-Davidson FLSTN Softail Deluxe |
| 2005-2006 |
Harley-Davidson FLSTNI Softail Deluxe |
| 2000-2003 |
Harley-Davidson FLSTS Heritage Springer |
| 2005-2007 |
Harley-Davidson FLSTSC Softail Springer Classic |
| 2005-2006 |
Harley-Davidson FLSTSCI Softail Springer Classic |
| 2001-2003 |
Harley-Davidson FLSTSI Heritage Springer |
| 1999-2002 |
Harley-Davidson FLTR Road Glide |
| 2007 |
Harley-Davidson FLTR Road Glide |
| 2002-2006 |
Harley-Davidson FLTRI Road Glide |
| 2008-2009 |
Harley-Davidson FXCW Rocker |
| 2008-2011 |
Harley-Davidson FXCWC Rocker C |
| 1999-2007 |
Harley-Davidson FXD Dyna Super Glide |
| 2007 |
Harley-Davidson FXDB Street Bob |
| 2006 |
Harley-Davidson FXDBI Street Bob |
| 2005 |
Harley-Davidson FXDC Super Glide Custom |
| 2007 |
Harley-Davidson FXDC Super Glide Custom |
| 2005-2006 |
Harley-Davidson FXDCI Super Glide Custom |
| 2004-2006 |
Harley-Davidson FXDI Dyna Super Glide |
| Attributes |
| Air Box Included |
No |
| Air Filter Color |
Red |
| Air Filter Height |
1.625 in (41 mm) |
| Air Filter Inside Diameter |
6.188 in (157 mm) |
| Air Filter Material |
Cotton Gauze |
| Air Filter Outlet Shape |
Not Flanged |
| Air Filter Shape |
Round |
| Air Filter Washable |
Yes |
| Alternate Part Number |
RK-3909-1 |
| ASIN |
B006OL1576 |
| California Proposition 65 |
WARNING: Cancer and Reproductive Harm - www.P65Warnings.ca.gov |
| CARB EO Number |
D-269-35/55 |
| Clamp Color/Finish |
Not Applicable |
| Clamp Material |
No Clamps Required |
| Clamp Style |
No Clamps Required |
| Clamps Included |
No Clamps Included |
| Color / Finish |
Red Filter, Metal Top |
| Country of Origin (Primary) |
US |
| Couplers Included |
None |
| Emission Code |
Legal US |
| Estimated Horsepower Gain |
6.05 HP @ 5206 RPM |
| Harmonized Tariff Code (Schedule B) |
8421310000 |
| Hazardous Material Code |
N |
| Horse Power Increase |
6 HP |
| Inlet Diameter |
2.25 in (57 mm) |
| Life Cycle Status Code |
Available to Order |
| Mass Air Flow Sensor Adapter Included |
No |
| Mounting Hardware Included |
Yes |
| NAFTA Preference Criterion Code |
B |
| Neck Flange |
2.25 in (57 mm) |
| Oil Included |
Yes |
| Overall Height |
1.688 in (43 mm) |
| Package Material |
Paperboard |
| Package Type |
Box |
| Product Box Height |
4.88 in (124 mm) |
| Product Box Length |
11.75 in (298 mm) |
| Product Box Width |
9.5 in (241 mm) |
| Product Style |
Motorcycle Intake System |
| Replacement Filter |
E-3972 |
| RPM |
5206 |
| SDR Required Flag |
N |
| Size |
7 Inch |
| Street Legal In All US States |
See Application Link Above, Not legal for sale or use in California on any pollution controlled motor vehicle. NOTE: Some specific models and years may be legal in CA. Check the CARB status on your parts at knfilters.com. |
| Style |
Oval |
| Top Material |
Black Powder Coated |
| Top Style |
Metal |
| TUV Approved (Europe) |
No, No |
| Warranty |
No-Hassle Lifetime Limited |
| Weight |
3.3 lb (1.5 kg) |
| GTIN |
00024844294135 |
