When the R90S was released 30 years ago, it changed the popular perception that BMW motorcycles were staid, stodgy, and only suitable for wealthy geriatrics. Hans Muth creating a styling masterpiece, and the R90S was a real Superbike. Yet while swift and comfortable, it came in for some criticism regarding high-speed stability. The handlebar mounted fairing, with its high steering inertia, accentuated this instability, and Muth was asked to create a new motorcycle, with a more integrated aerodynamic fairing. The result was the R100RS, arguably even more significant than the R90S. Underneath the large fibreglass fairing was also the most powerful incarnation of the boxer yet, and the R100RS created a sensation when it was released at the Cologne Show towards the end of 1976.

Fairing
The R100RS was rare in having a design incorporating bodywork providing rider protection, aerodynamic function, and motorcycle stability. The nine-piece fairing design was so advanced that it remains a benchmark in motorcycle fairing efficiency, and few later examples can match it. But there was more to the R100RS than an efficient fairing. The engine was bored to 94mm to provide 980cc, and with larger valves, the power went up to 70 horsepower at 7250rpm. Instead of the concentric Dell'Orto carburettors of the R90S, the R100RS received Bing 40 mm constant-vacuum carburettors. Although the frame and swingarm were essentially unchanged, a second transverse tube was added between the front double downtubes and the frame tubing was a thicker section. Despite these welcome improvements, the front fork still included the weak pressed steel upper triple clamp, and the rear subframe was bolted on as before. Most early R100RSs were fitted with spoked wheels, with a drum rear brake, but from 1978, all RSs came with snowflake cast alloy wheels with a rear disc brake.

If the R90S stretched the sporting boundaries with its low handlebar and semi-racer riding position, the R100RS took this a step further. The narrow, clip-on style handlebar fitted inside the fairing, and provided a surprisingly aggressive riding position. Considerable weight was placed on the wrists, encouraging high-speed touring. There was also the choice of a standard dual, or sporting solo, almost one and a half, seat.

Updates
Updates to the R100RS came almost annually through until arguably the finest model, the 1981-84 series. For 1979, the camshaft drive was completely revised, there was an automotive-style rotary contact breaker ignition, an oil cooler, and torsional vibration damper added to the driveshaft. Most development was saved for the 1981 model. This year saw Galnikal cylinders, electronic ignition, a plastic airbox with flat air filter, a much lighter flywheel and clutch assembly, and superior Brembo front brakes. The front brake master cylinder also was moved from underneath the fuel tank to the handlebar

The R100RS was one of the most expensive motorcycles available in the late 1970s and early 1980s. And despite retaining a relatively unsophisticated engine, it could still match any other sport-touring motorcycle, even its replacement, the K100RS. The weight was a moderate 210kg, the fairing made it an incomparable road burner, and while the K100 has vanished into obscurity, the R100RS had become another classic BMW.

Auteur: Ian Falloon
Bron: Bike Point Australia