In 1977, BMW saw the opportunity to broaden its range, creating the R100RS sport-touring model with a full fairing. The R100S slotted in just below as the specialist sportbike. To create this new /7 series, from which the RS and S derived, BMW stiffened the frame with thicker tubing. Of course, it was heavier, too, and the R100S crossed the 500-lb threshold. It coped by incorporating many changes to the engine. The air-cooled, overhead-valve, horizontally opposed twin now displaced 980cc, with bore and stroke at 94.0 x 70.6 mm and a 9.5:1 compression ratio. The former Dell’Orto accelerator-pump carburetors gave way to 40mm Bing constant-velocity carbs, mainly for reduced emissions but this incidentally resulted in easier cold starting.

With 65hp at 6,600 rpm, the 1977 BMW R100S turned the quarter-mile in 12.97 seconds at 103 mph, one of just four bikes that beat 13 seconds for Cycle magazine. Another source reported top speed at 121 mph. The test by Cycle also yielded 40.5 mpg. Twin disk brakes were at the front, and various other improvements came from clever solutions to fit the package size. The electric starter gained cranking power thanks to a revised flywheel, while a stronger clutch made the connection between the engine and five-speed gearbox, which nevertheless drew the same old complaints about deliberate shifting and the resultant clunking.

At 2.91:1 instead of 3.0:1, the taller rear axle ratio made for more relaxed highway cruising. The low handlebar accommodated a redesigned clutch lever, and the compact new ignition key pleased nearly everybody. The $4,195 price tag didn’t deter connoisseurs. As summed up by Cycle, the R100S “remains completely a BMW: fast, quiet, comfortable, very expensive and utterly unique.”