K&N Cold Air Intake System RK-3950

Technical details

A stock intake can feel like a bottleneck when you want your motorcycle to respond more freely under acceleration. The K&N RK-3950 cold air intake system is designed to create a less restrictive path for airflow, bringing more cool, oxygen-rich air to the engine. K&N says this can increase horsepower and torque, but the product information does not give specific gain figures, so treat the improvement as a claimed benefit rather than a guaranteed result for every bike.

The kit includes a high-flow air filter, and K&N says its horsepower and torque testing uses wheel-based dynamometers, with reports included with each intake system. It also describes a more pronounced engine growl on acceleration that quiets down once you’re at speed. Those details matter if you want a performance-oriented intake, not just a replacement filter.

Compatibility

This system is listed for select 2013–2015 Harley-Davidson FLSTN Softail Deluxe and FLSTC Heritage Softail Classic motorcycles. The wording is specific: it does not establish fit for every Harley-Davidson or every year of those model lines. Match your motorcycle’s exact model and year to the product’s fitment information before choosing it. The compatibility details provided here do not include an installation guide or a full list of supported configurations.

For owners of a listed Softail, the appeal is an intake intended to support freer breathing without moving to a different motorcycle or a broader engine modification. If your bike is outside the named models and years, this listing alone is not enough to confirm fit.

Usage tips

Think about how you ride before choosing a high-flow intake. For everyday or highway use, the claimed gains in throttle response and engine sound may be more relevant than a large peak-power figure, no specific horsepower or torque numbers are provided here. A practical example is rolling on the throttle to merge or climb a hill: K&N presents improved response and uphill performance as benefits, including when towing, but the actual result can vary with the motorcycle and setup.

From the way it is set up, this is a targeted intake upgrade rather than a universal performance fix. It suits you if you own one of the listed Softails and want an airflow-focused change with a more audible engine note. It might not be a great match if you need confirmed fitment for a different year or model, or if you’re buying based on a precise power increase that this listing doesn’t quantify. K&N also says the intake will not void the manufacturer vehicle warranty and includes a no-hassle lifetime limited warranty, check the supplied warranty terms for the details that apply to your purchase.

Questions before you buy

Does the system include a high-flow air filter? Yes. The product name and description identify a high-flow filter as part of the intake system.

Are horsepower gains specified? No exact figures are given here. K&N says its testing reports are included with each intake system, but the product information provided does not state a result for this fitment.

Will it change the sound? K&N describes a stronger growl during acceleration that returns to a quieter sound once you’re at speed. The listing does not give a sound measurement.

Is it worth it?

The RK-3950 makes the most sense as a model-specific intake upgrade for a listed Softail owner who values freer airflow and a more noticeable engine note, and who is comfortable with performance claims that aren’t quantified here. Its fitment range is narrow, so a rider with another bike—or anyone prioritizing a documented power number—has a good reason to look at a different approach. If your model and year match, the included filter and stated dyno-report approach give you more to assess than a generic airflow claim alone.