BMW K100
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- For the radio station in Saint John, New Brunswick, see CIOK-FM.
In the late 1970s, following several years of declining sales, BMW motorcycle engineers began work on developing a replacement for the aging flat-twin engines. The design team lead by Josef Fritzenwenger and Stefan Pachernegg eventually developed a design based on a Peugeot car engine, in which a four cylinder engine was laid on its side across the motorcycle frame. This is known as a longitudinal four because the crankshaft is in line with the direction of travel of the motorcycle. Unlike the flat four engine, however, which is also longitudinal, the cylinders of the K engine were not divided by the crankshaft, as are the pairs of cylinders on the flat four engine found in the Honda Gold Wing.
The original K engine has its four cylinders arranged so that the crankshaft is on the right-hand side of the motorcycle, with the cylinders, pistons, camshafts, injectors and sparkplugs on the left-hand side. This arrangement keeps the centre of gravity relatively low, which benefits handling. In addition, since the crankshaft is now on the right-hand side, access to the engine becomes much easier than in a conventional design, where the crankshaft is at the bottom (hence the term "bottom end").
This configuration, although technically not new for motorcycles, had not been seen for many years. It had certainly not been used by any major motorcycle company, let alone one as conservative as BMW, which had been using the flat-twin ever since 1923.
