In 1938 BMW released a whole series of new models: the 250cc R 23 , the 500cc R 51 with OHV engine, the 600cc R 61 side valve, the 600cc R 66 OHV and the 750cc R 71 side valve. The R 61 thus became the successor to the R 6. 3,747 units of the R 61 were produced between 1938 and 1941 . The sister model was the sports bike R 66.
source/image(PrtSc): classic-motorcycle.com
The R 61 had the new oval tube drawn double cradle frame that would serve well into the 1950s. Completely new was the applied plunger suspension , which gave a BMW rear suspension for the first time. 200mm drum brakes were used front and rear.
The engine was simply mounted in the frame with two thru-axles , a construction that would last for a long time. The side valve engine was almost identical to that of the R 6.
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The single dry-plate clutch was operated with a push rod running right through the main shaft of the gearbox. This system remained intact until 1996 ( R 100 R Mystic ).Like the racing bikes , the R 61 got foot gear (4 gears)./wikipedia
- Manufacturer: BMW
- Model: R61
- Year: 1938
- Displacement: 600 cc
- Cylinder: 2 – transverse
- Engine type: 4-stroke / sv
- Bore / Stroke: 70 x 78 mm
- Power: 18hp @ 4.800 rpm
- Compression Ratio: 1 : 6.0
- Weight: 184 kg
- Top Speed: 115 km/h
