In 1959, BMW struggled against falling motorcycle sales, financial crisis and even a hostile takeover bid. Eventually BMW retained control of its own destiny as an independent motorcycle and automobile manufacturer and plans were made to introduce a new generation of motorcycles. But it took one man’s courageous decision to say “yes” to a new and costly development schedule of improved ‘Boxer-powered’ machines. These plans formed the basis for BMW’s motorcycling fight back and the eventual introduction of another range of iconic ‘Boxer-engine’ models – the ‘slash-5’ series.
At the beginning of the 1960s, BMW was still reeling but riding the storm of a downward trend in motorcycling popularity. This unknown trend wasn’t helped by low value second-hand cars and BMW’s own automobile division churning out affordable four-wheelers in an effort to combat rising competition. Because of this, BMW’s board of directors were not prepared to place finances into a division of its business that was in serious decline – only 4,300 BMW motorcycles were sold in 1962, of which a greater percentage were exported. However, the upper floors of BMW were also not prepared for the passion and dedication of BMW Technical Director Helmut-Werner Bönsch.
As a lover of all things motorcycle, it was Helmut-Werner Bönsch who lobbied and appealed to the other BMW directors and majority shareholder Herbert Quandt for a new direction in motorcycling, citing the growing American demand for bigger and sportier machines, along with the threat of Honda of Japan taking on the mantle of motorcycle greatness.
The next step in ‘Boxer-powered’ motorcycle history eventually started in 1963. The first new prototype – designated Type 246 – for many years appeared in a rough guise of an R 69 S engine bolted inside a new frame, which bore more than a passing resemblance to the famous Rex McCandless featherbed racing frame built for Norton. The test mule also brought a return to hydraulically damped telescopic forks that BMW had pioneered nearly 30 years earlier. In typical BMW fashion, the test machine evolved into an off-road machine and was entered into competitions for durability tests.
In 1964, another man appeared in the offices of BMW. Hans-Günther von der Marwitz had already achieved design success with several German bike manufacturers before their demise and also Porsche, and the offer to join BMW was too good to dismiss – especially as his love for two wheels was greater than four!
As head of the Testing Department, it’s fair to say Marwitz was like a kid in a sweetshop and his became the main voice to be heard in making the 246 range of proposed motorcycles all sportier options, as opposed to the usual group of touring bikes and one slightly more performance oriented. Indeed, it turned out that none of the bikes were to be built with provision for sidecar attachment because Marwitz wanted the new bikes to handle the same – if not better than – sportier British offerings.
Development of a new engine to suit the developing 246 chassis was overseen by Alex von Falkenhausen and Ferdinand Jardin. The resulting engine design was considered to be the first true modular BMW engine. The new engine featured a taller crankcase that rose up to the fuel tank. This was just so to incorporate an electric starter motor – a first for BMW, as was the use of 12v electrics.
The traditional pushrods were placed under the cylinders to leave the topside of the cylinders free from clutter and greater airflow across the deep cooling fins (a very plausible reason why this is engine is commonly referred to as the ‘Airhead engine’). This simple move was achieved by moving the camshaft under the crankshaft and being driven by a Duplex chain instead of bulky gears – a direct result of Falkenhausen’s automobile development, itself a technical descendant of earlier Boxer engines.
To say the engine was all-new is an understatement. Reliability was at the forefront of design rather than outright power. Oil pumping, oil scavenging feed and return design were key points and were reflected in the Eaton-type oil pump that could deliver 1400 litres of life-giving oil at 6,000 rpm. New crankshaft and crankcase designs were part and parcel of the new engine, which took on a curvaceous look to make it exquisitely modern. It was then decided the new engine should become a platform for three different capacities.
In 1969, the design team’s labours bore fruit with the reveal of three new models for the model year 1970. These machines consisted of 500, 600 and 750cc variants and were known as R 50/5, R 60/5 and R 75/5, more commonly known as the ‘slash-5’ models. A new generation of BMW motorcycle had indeed been created. BMW management now held its breath while waiting for press and public opinion and, more importantly, whether the new bikes would help rekindle the public’s love for motorcycling.