BMW K100

The BMW K100 is a family of four-cylinder 987 cc motorcycles that BMW manufactured from 1983 to 1992. Since the 1920s BMW had built air-cooled flat-twin boxer motorcycles, culminating in the 980 cc R100 of 1976, but by the end of the 1970s emissions rules in the United States and the European Union demanded finer control of the fuel entering the combustion chamber, which was easier with more cylinders of smaller displacement, and Japanese makers were building smoother, quicker four-cylinder machines, so BMW needed a clean-burning four quickly. A flat-four would have suited its boxer tradition but would have looked like a copy of the Honda GL1000 Gold Wing. In 1977 Josef Fritzenwenger presented a prototype using a PSA-Renault X-Type engine from a Peugeot 104, laid flat in the frame with the crankshaft on the right, running parallel to the centre line of the frame.