R 45 (reduced effect)

1981 BMW R 45 (reduced effect) Technical Analysis & Specification Breakdown

Positioned in BMW's sport touring motorcycle lineup, the 1981 BMW R 45 (reduced effect) pairs a 473 cc (28.9 cu in) air-cooled two cylinder boxer, four-stroke architecture with road-focused gearing. In factory specification, peak output is rated at 27 HP (19.7 kW) at 6,500 rpm, transferring power to the rear wheel through a 5-speed gearbox and shaft drive (cardan) final drive. With a specific output of 57.1 HP per liter, the engine character is prioritizing low-RPM tractability, mechanical longevity and relaxed throttle response over peak redline numbers.

On the scales, the R 45 (reduced effect) measures 206 kg (454 lbs) wet (curb), translating to a power-to-weight ratio of 0.13 HP/kg (7.63 kg per horsepower). The 22-liter (5.8 US gal) fuel tank supports practical everyday commuting and weekend road stints, while factory top speed is listed at 141 km/h (88 mph).

Within MotoLibrary's BMW archive, this model family spans 7 indexed model years from 1978 to 1984, allowing buyers to track year-over-year changes in emissions tuning, weight and equipment.