Perhaps it is the last major innovation of the BMW company on the motorcycle sector. Of course it's not a world novelty, as one want us to make clear until today. Nimbus and Ariel yet have mounted longitudinally in-line four-cylinder, although air-cooled and only at Ariel horizontal.
Here are the current models with transverse engine conceptually not more imaginative, even if they are constructed much more complex and as a result much more afford. We write the year 1979. BMW has reached probably the lowest point of motorcycle admissions. The two-cylinder boxer appears to have reached the end of its development.
BMW without motorcycle construction, is that even possible? After all, one already have to give up the aircraft engines factory. And self-designed motorcycles are produced longer than cars. As you know one have not given up, but it's something new emerged, the K-series. That is the power of BMW, new things to combine with proven. The engine becomes a liquid-cooled in-line four-cylinder engine, while the drive shaft remains.
To keep the center of gravity low, the motor is mounted on the side, a quite common practice with underfloor engines. Initially to the right, but then the exhaust tract and the shaft swingarm come together on one side. So the other way around. Just one experiments with Peugeot engines, but they prove to be too heavy and too unwieldy. Even the plan, to develop directly and synchronistically a vehicle engine.
Instead a three-cylinder shall be created. It will come two years later as K 75 to market. Thereto an already existing shaft in the crankshaft turned into a balance shaft. Anyway it avoids the teething troubles of its big brother. Even then it has more than three-quarters of the performance, which indeed not brings many fans at home, but in the spedd-limited countries even more.
Here the K sold 100 well, indeed has lot to offer. It will be the first motorcycle with electronic fuel injection, though not yet with motronic, but already with maintenance-free transistor ignition. Later still follows, though not without problems, even ABS, again for a motorcycle a world first. Nominally the K-series are still available from the factory, but as said not even quite comparable. 11/10