BMW R 50 S / R 69 S.
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The BMW R 50 S was a motorcycle that Bayerische Motorenwerke built 1634 times from 1960 to 1962 - a difficult economic period for the company. It was the performance-enhanced, sporty version of the basic model BMW R 50 with a two-cylinder boxer engine . In 1960 the R 69 S also appeared , which was manufactured until 1969.
History and construction
Technically, the R 50 S largely corresponded to the standard R 50 model with a double loop tube frame, a pushed swing arm at the front and a swing arm with two spring struts at the rear. There was also a hydraulic steering damper instead of the mechanical one on the R 50. The increase in performance of the 500 cm³ engine from 26 hp to 35 hp was essentially due to a higher compression ratio (9.2: 1 instead of 6.8: 1), higher speed ( 7650 rpm instead of 5800 rpm) and carburetor with an enlarged passage from 24 mm to 26 mm.
In 1962, the crankcase ventilation was improved, and changes to the carburetors improved the mixture formation when cornering.
In 1960 the 42 hp R 69 S replaced the R 69 with 35 hp. With a top speed of 175 km / h (lying down, sitting upright 160 km / h, information according to the operating instructions), this 600 series BMW was one of the fastest motorcycles of its time. In many of the first vehicles, serious engine damage occurred at an early stage with torn off cylinders, defective crankshafts and destroyed engine housings; An effective remedy, however, from 1963 onwards was the torsional vibration damper mounted on the front crankshaft stub. Its space requirement required a modified front housing cover with a slightly bulged lower half - see "bump" in the picture - and a slightly modified front swing arm with a flattened section on the lower fender support pipe bend. Production of the R 50 S was discontinued after just over a year, and the factory recommended retrofitting with the vibration damper for this model as well.
The chassis of the R 50 S and R 69 S are largely identical. However, the R 69 S was also supplied with a front telescopic fork, especially in the USA. On request, a 24-liter tank was available ex works for the R 69 S, while accessory providers (e.g. Heinrich and Hoske ) offered other tank sizes for almost all BMWs. The so-called ox-eye indicators on the handlebars were available as factory accessories for all models.
The R 69 S was the first BMW motorcycle to be available ex works in ivory instead of black paintwork at the customer's request.
The engines of the “S” models - as well as those of the R 68 and R 69 - can be recognized by their wider valve covers with only two instead of six longitudinal ribs of the R 50 / R 60.
Technical specifications
| Model: | R 50 S | R 69 S |
| construction time | 1960–1962 | 1960-1969 |
| Engine type | Two-cylinder boxer | |
| Valve control | Central camshaft, OHV , 2 valves per cylinder | |
| Displacement | 494 cc | 595 cc |
| Bore × stroke | 68 × 68 mm | 72 × 73 mm |
| compression | 9.2: 1 | 9.5: 1 |
| power | 26 kW (35 PS) at 7650 rpm | 31 kW (42 hp) at 7000 rpm |
| Carburetor | 2 bing, 26 mm | |
| ignition | Bosch magneto ignition | |
| transmission | 4 gears (foot switch), cardan drive | |
| frame | Double loop tubular frame | |
| wheelbase | 1415 mm | |
| Front and rear tires | 3.50-18 | |
| Brakes front and rear | Drum, Ø 200 mm | |
| Empty weight | approx. 200 kg | |
| Tank capacity | 17 l | |
| Top speed | 160 km / h | 175 km / h |
| price | 3,535.00 DM | 4,030.00 DM |
| number of pieces | 1,634 | 11,317 |
R 50 S and R 69 S in motorsport
Private drivers use both the R 50 S and the R 69 S in motorsport, but mainly with sidecars in sidecar races. These machines with bumper engines had little to do with the much lighter RS machines in common, which were characterized by engines with overhead camshafts.
See also
literature
- Wolfgang Zeyen, Jan Leek: BMW - The motorcycles since 1923 . Motorbuch Verlag, Stuttgart 2004, ISBN 3-613-02401-2 .
- Dorothea Briel: BMW - The Motorcycles . Paul Zsolnay Verlag, Vienna 1993, ISBN 3-552-05084-1 .
- Hans-Joachim Mai: 1000 tricks for fast BMWs . Motorbuch-Verlag, Stuttgart, 3rd edition 1972.
Web links
- BMW R 50 S. In: BMW History. BMW AG, accessed on November 24, 2019 (dossier in the BMW Group Archive).
- BMW R 69 S. In: BMW History. BMW AG, accessed on November 24, 2019 (dossier in the BMW Group Archive).
- Handbook Motorcycles R 50, R 60, R 69 S, R 50 S. (PDF) In: BMW History. BMW AG, April 1961, accessed on November 24, 2019 (operating instructions with pictures, 99 pages).
- BMW R 26, R 27, R 50, R 50 S, R 60, R 69 S. (PDF) Original BMW spare part. In: BMW history. BMW AG, March 1966, accessed on November 24, 2019 (spare parts list with pictures, 322 pages).
Individual evidence
- ^ Dorothea Briel: BMW - The motorcycles . VIP motor, Paul Zsolnay Verlag, Vienna 1993, ISBN 3-552-05084-1 .
- ^ Jan Leek: Type compass BMW - Motorcycles since 1945 . Motorbuch Verlag, Stuttgart 2012, ISBN 978-3-613-03475-4 .
- ↑ A vibration damper on the crankshaft had already been developed for the BMW 700 car ; it reduces crankshaft vibrations to less than a third. Source: Helmut Hütten: Fast engines - dissected and coiffed. Motorbuch-Verlag, Stuttgart, 10th edition 1994, ISBN 3-87943-974-5 , there page 312, Fig. 11.3.
- ↑ Wolfgang Zeyen / Jan Leek: BMW - Motorräder since 1923 , Motorbuch Verlag, Stuttgart 2004, ISBN 3-613-02401-2 .
