One of the three major lines of BMW motorcycles, in addition to Airhead twins (1923-1996) and Oilhead twins (1993-present).

They feature an odd but effective engine configuration, with the cylinders laid on their side, DOHC heads to the left and crankcase on the right. This configuration leads to a very low centre of gravity, giving K-bikes a very light feel in low-speed maneuvering.

The K stands for "Kompakt", which makes sense if you compare them to the width of BMW's existing Airhead motors at the time when the K-series was introduced.

The K series introduced several innovations that were rare or unheard-of in the motorcycle market until its introduction:

  • Electronic fuel injection
  • Electronic ignition
  • Electronic instrument panel

The K line comprises:

Rumours have been circulating for years that BMW is planning to replace the K series, down to two (albeit popular and well-regarded) models in recent years, with an entirely new design, possibly a four-cylinder boxer.

Nicknames:

  • K-whiner: K-bikes are generally very quiet, and produce a unique whining or whistling sound.
  • Flying Brick: The K engine looks a bit like a large aluminum brick.