BMW R90S
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| Manufacturer | BMW Motorrad |
|---|---|
| Production | 1973–1976 |
| Class | sport motorcycle |
| Engine | 898 cc Four-stroke, two-cylinder, horizontally opposed "Boxer", air-cooled |
| Bore / stroke | 90 mm × 70.6 mm (3.54 in × 2.78 in) |
| Top speed | 200 km/h (120 mph) |
| Power | 67 hp (50 kW) |
| Torque | 76 N·m (56 lbf·ft) |
| Transmission | 5-speed, shaft drive |
| Brakes | Front: dual 260 mm discs Rear: 200 mm drum |
| Tires |
Front: 19 in (480 mm) Rear: 18 in (460 mm) |
| Wheelbase | 1,465 mm (57.7 in) |
| Dimensions |
L: 2,180 mm (86 in) W: 740 mm (29 in) H: 1,210 mm (48 in) |
| Seat height | 820 mm (32 in) |
| Weight | 215 kg (474 lb) (wet) |
| Fuel capacity | 24 l (5.3 imp gal; 6.3 US gal) |
| Related | R90/6 |
Front: 19 in (480 mm)
The BMW R90S is a 900cc sport motorcycle produced by BMW from 1973 to 1976. BMW commissioned designer Hans Muth to oversee the R90S, which became the flagship of the boxer engined "/6" range. Sporting distinctive two-tone paintwork, a bikini fairing and a new tail, the R90S was intended to shrug off the enduring image of BMW bikes as staid and utilitarian.
The 67 bhp (50 kW) R90S had a top speed of 124 mph (200 km/h), it ran the quarter mile in around 13.5 seconds and it accelerated from 0 to 62 mph (0–100 km/h) in 4.8 seconds. Maximum torque was delivered at 5,500 rpm and the engine redlined at 7,200 rpm.
The R90S' type 247 "airhead" engine was a pushrod OHV, two valve per cylinder, air-cooled flat-twin "boxer" unit. The engine was based closely on the R75/5, sharing the same stroke, but with a larger bore, to give a capacity of 898cc. The R90S weighed 215 kg (474 lb) and has a five-speed gearbox with a shaft final drive. The first R90S models had a two-tone paintwork scheme of "Smoke Black/Silver" with adhesive gold pinstripes. Feedback from unimpressed customers prompted BMW to return to hand painted pinstripes. Later R90S models were available also in two-tone "Daytona Orange" with red pinstriping. The R90S had a redesigned seat, with a small "ducktail" fairing which (in addition to an underseat tool tray) provided a small storage space lightweight items such as waterproofs. Standard equipment included a full toolkit, a hand pump, a first-aid kit and even a small hand towel with an embroidered BMW logo.
The R90S had a small bikini fairing which housed four analogue instruments: a speedometer, tachometer, clock and voltmeter. Its 238 watt alternator was later upgraded to 250 watt. An adjustable hydraulic steering damper was manually adjusted via a knob on the steering head. Suspension was by long-travel telescopic forks and twin rear shocks whose rear dampers were adjustable for preload (the only suspension adjustment available). Whereas other BMW boxers had Bing slide constant velocity carburetor, the R90S was fitted with accelerator pump Dell'Orto carburetors. The R90S engine had a 9.5:1 compression ratio, while the less sporty R90/6 had a ratio of 9:1.
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