BMW R 42 – year 1926
Manufacturer: Bayerische Motoren Werke AG, Munich, Germany
The first mass-produced R 32 - with a blue and white propeller mark on the factory emblem - it stayed, after four years of production (w 1926 year), replaced by an improved and stronger type BMW R 42. The new motorcycle retained the overall design concept of the previous model, i.e.. lateral positioning of the boxer motor, Power transmission to the rear wheel by means of a shaft with joints and a double tubular frame.
However, the design office of the Munich-based factory made BMW R. 42 some significant improvements. The motorcycle already had an engine with removable cylinder heads and a new air intake system (air was now being drawn in from the space around the flywheel, which also served as a vortex filter). The block brake has been replaced with a foot brake, acting on a shaft with cardan joints. Engine with a low valve timing (with a cylinder diameter equal to the stroke of the piston – 68 mm) had unchanged cylinder capacity 493 cm3. The power, however, rose to 9 kW (12 KM) at 3400 rpm. Blocking the engine with a friction disc clutch, connected to the flywheel and the three-speed gearbox made the engine run exceptionally smoothly. Installations: ignition (magneto type) and lighting came from Bosch. Angular fuel tank, adapted to the double tubular frame, comfortable aluminum footrests and encapsulated all-mechanisms were typical of this motorcycle. The front suspension with a fork and short trailing arms was sprung with a leaf spring. Rear wheel – suspended rigidly. In addition to the brake on the drive shaft, there was one more (jaw, manually operated), which acted on the front wheel.
The motorcycle had a curb weight 126 kg and developed maximum speed 100 km/h. Fuel consumption was within limits 3,5-4,5 liter of 100 km. Model R 42 was produced until 1928 year, in which it was replaced by the BMW R 52 with long stroke motor, for the first time used in the company's vehicles.