After nearly sixty years of producing flat twin engined machines of very high quality but basically simple specification, BMW gave the motorcycling world something of a shock when the K100 was first announced late in 1983.
At first glance it seemed the complete opposite of all those qualities that the company had previously found so important in a motorcycle, but on closer inspection it becomes obvious that great efforts have been made to make the machines as light, simple, and compact as possible and yet attractive to the modern motorcyclist. The design is intended to provide a sound basis for a long-running production, taking into account all current and pending noise and emission control legislation.
Research started in the mid-1970's into a replacement for the flat twin engines, which are already approaching the limits of reasonable development. A breakthrough came in 1979 with the patenting of the basic idea of taking a car engine, laying it on its side and transmitting the drive through a secondary output shaft. This provides a low center of gravity and a very distinctive appearance, as well as the basis for a short compact engine/transmission unit. The transmission is very similar in layout to that used on the twins but is totally redesigned, using lightweight materials wherever possible, with emphasis on keeping it as short and as compact as possible. The tubular spine type frame is bolted to the unit and carries a pair of conventional telescopic forks to provide steering and front suspension.
After the introduction of the K100 and K100RS in late 1983,followed by the K100RT in 1984 the machines suffered one or two teething troubles, as is inevitable with any brand-new design, which were soon rectified by the introduction of modified components. In addition to this, one or two modifications have been made to cure problems, which became evident in service; notably to reduce vibration and the build-up of heat under the fuel tank.
When the 750cc models ware introduced, starting with the K75C in late 1985, the opportunity was taken to modify many 100-modelcomponents to take advantage of commonality of parts; BMW claim approximately 70% of the components are common to both models. The development of the smaller machines proceeded alongside the 100 models but introduction was delayed until 1985/86; as a result the 75-models incorporate all the lessons learned from the earlier 100-models.
In common with their policy in previous years, BMW introduced various forms- of each basic model to cater for as many tastes as possible. Thus the basic K100 was followed by the sports/touring K100 RS, the touring K100RT and the fully-equipped K100LT tourer. The first 75-model was the K75C, which was followed by the more sports-orientated K75S and then the basic K75.
In all cases (except for final drive ratios, the sports suspension on the K75S and the rear wheel and brake on the K75 and K75C) the basic machine is exactly the same. Note: To avoid confusion with the basic K75 and Kl00models, machines are refered to throughout the manual as '75' models or '100' models, except where a more precise definition is required.
Refer to Chapter 11 for details of the 1988 on models.
The first BMW motorcycle
1983 - The first K100 model
1983 - The K100RS model
1984 - The K100LT model
1985 - The K75C model
1986 - The K100LT Tourer model