2023 Drake Smith - Please do not use or reproduce this elsewhere.  Feel free to link to it though.

Why A K&N Air Filter Does Not Make Sense For A K Bike

Mahle LX 75 Air Filter


Disclaimer: This is just my opinion and my rationale for it. If you disagree with me and want to run a K&N air filter in your K bike then go right ahead.

No Impact On Performance:

Although on some vehicles restricted air flow does limit power output that is not the case with K bikes.

1 - FILTER AREA: If you've dealt with other vehicles then you'll realize that the K bike air filter is very oversized for a 750, 1000 or 1100cc engine. Therefore it does not restrict the flow of air that the engine needs for optimal combustion.

2- DYNO TESTS: As noted at the bottom of this web page, Don Eilenberger and Brian Curry conducted dyno runs of a K75 under four different scenarios:

          1 - Regular BMW/Mahle LX75 air filter

          2 - Half of regular air filter covered in Saran Wrap

          3 - No air filter

          4 - K&N air filter

The dyno measured power output was the same for all four of those scenarios.


The BMW recommended replacement interval for the air filter is 12,000 miles. In my experience, unless you run a K bike in an extremely dusty environment, the air filter will easily last 50,000 miles or more so I replace the air filter every 50,000 miles whether it needs it or not.

K&N recommends cleaning and re-oiling their air filters every 10,000 miles. Given how hot a K bike engine compartment gets I suspect that the filter oil may dry out in less than that so if I were to run a K&N air filter then I would probably re-oil it every 5-6,000 miles.

Not to mention that even on K bikes without the air box covered by the fairing (standards and K75C) air filter maintenance is a PITA so the less you have to deal with the air filter the better.

Engine Wear:

One of K&N's marketing claims is that their filters keep more "dirt" out which prolongs engine life by reducing wear. K bike engine cylinders are lined with Nikasil so the engines last hundreds of thousands of miles using stock air filters. The rest of the bike usually falls apart before the "bulletproof" engine does. Mahle has a reputation for making high quality air filters.


As of this writing, the cost for a K&N K bike air filter is $75.98 on Amazon. And then you need to periodically buy K&N cleaning/re-oiling kits (about $18) to service it.

Mahle LX75 air filters currently cost $36.11 (plus shipping) at Euro  MotoElectrics.


K&N Air Filter:



You get a cool K&N sticker No performance improvement
  More frequent maintenance
  Higher up front and ongoing cost

Engine wear is probably a toss-up


2023 Drake Smith - Please do not use or reproduce this elsewhere.  Feel free to link to it though8