Contemporary accounts rated the BMW R90S as a cutting-edge sport bike with a high level of specification and performance, and at its introduction in late 1973, the R90S startled those accustomed to conservative BMW styling. The 6.4-gallon tank received a two-tone black and silver paint scheme with gold adhesive striping, although Daytona Orange with red striping became available later, so the R90S was a real attention grabber. The seat with integrated grab rail was redesigned from the R75/5, upon which this bike was based, and the enclosed tail section completed the cafe racer influence. In case you remained unsure, the side cover carried a huge 900cc decal.

BMW obviously had big plans for the Disco Era. Inside the fairing, the instrumentation included an ammeter and clock. The air-cooled, overhead-valve horizontally opposed 898cc twin had been bored out to 90.0 x 70.6 mm. Compared to the R90/6, the R90S had a slightly higher 9.5:1 compression ratio, high-performance camshaft, and 38mm Dell’Orto accelerator-pump carburetors. At first, ticklers were used to prime them but by late 1974 the carbs had chokes for cold starting.

The output of 67hp let the 1974 BMW R90S run from 0 to 60 mph in 4.8 seconds and surpass 120 mph. It now had a five-speed gearbox with the shift mechanism revised from R75 models, and of course there was shaft drive. Braking improved with dual perforated front disc and frame-mounted, cable-actuated master cylinder. Smooth and reliable, the R90S left behind the sidecar tradition forever. Priced almost inconceivably high at $3,430, it nevertheless flew out of dealerships. Slightly more than 6,000 of this classic model were produced.