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Cult bike BMW K 75

A motorcycle of reason?

The BMW K 75 never wanted to be: the motorcycle of reason. Sometimes she thrashed out when she was sent out onto the streets 30 years ago. In vain, as we know today.

M.ith a bang, BMW rose to become a motorcycle manufacturer in 1923: The world had never seen anything like the neatly designed R 32 with its longitudinally installed two-cylinder boxer, flange-mounted gearbox and shaft drive. When, despite the enormous success of their Enduro R 80 G / S, the Munich-based company was looking for a future without boxers in the early 80s, they looked for a similarly exciting solution – and invented the flying brick.

Cult bike BMW K 75

A motorcycle of reason?

Fluidbloc has been preventing wild fights since 1986

The BMW K 75 has three instead of four cylinders, which is why its crankshaft with a 120 degree crank pin offset produces more first-order mass moments. In order to control this, the output shaft, which is also present in the K 100 and on which the single-plate dry clutch is located, carries two counterweights. It works, only with 6000 tours it tingles a little. In order to achieve 100 HP liter output, the combustion chamber shape had to be radicalized, otherwise the engine follows the already tried and tested K principles: Two overhead camshafts each actuate two valves, a Bosch LE-Jetronic mixes and measures the mixture, a Relatively good five-speed transmission transmits the power to the cardan drive acting in the single-sided swing arm. Some uncertainty arose because the new one drives refreshingly different than the 100 series despite almost the same chassis data. Handier, more direct, not at all stiff and stubborn pushing it over the front wheel.

Small cause, big effect: thanks to the ten kilogram lighter engine, there is less load on the front wheel. But the joy of this arrangement was severely dampened when MOTORRAD plowed the bumpy slope with the BMW K 75 in the first comparative test and light pilots reported surprisingly dangerous handlebar knocking after driving over even small hilltops. BMW was horrified, but reacted in an absolutely professional manner and developed an effective solution in a very short time. The Fluidbloc, a friction damper made of special rubber inserted into the steering head tube, has been preventing wild brawls since 1986 without – like many hydraulic systems – negatively influencing high-speed stability or handling.

Uff, just went well again. Only now was the BMW K 75 able to pursue its real purpose: With unspectacular engine characteristics, very low fuel consumption, the highest practical disposition, tireless wanderlust and a now legendary durability, it became the favorite of all those who just want to drive all the time. And don’t need a show, because even the disguised versions S (sold from 1986) and RT (from 1990) lack any talent.

Rearview mirror PDF: Prototype BMW three-cylinder K 75 750 ccm (MOTORRAD 14/1983)

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The triple is just as reliable and linear as the four, but sounds much nicer from 6000 rpm.

Data (for model C Bj. 1985): water-cooled three-cylinder four-stroke in-line engine, 740 cm³, 55 kW (75 PS) at 8500 / min, 68 Nm at 6750 / min, five-speed gearbox, bridge frame made of tubular steel, weight fully fueled 236 kg, front tires 100/90 x 18, rear 120/90 x 18, tank capacity 21 liters, top speed lying down 200 km / h, 0-100 km / h in 4.8 seconds.

Scene: Of a total of around 68,000 BMW K 75s built between 1985 and 1996, most sales relate to the RT variant introduced in 1990. This was due, on the one hand, to their outstanding touring properties and, on the other, to government contracts from all over the world. What is most sought today are the ABS models that were also sold from 1990 onwards, regardless of whether they are uncovered, with handlebar cover (C), half (S) or full shell (RT). In the BMW cosmos, K 75 are considered a used bargain, even with mileage under 50,000 kilometers between 1,800 and 2,500 euros can be done. The technology is still familiar to every BMW mechanic, spare parts worries are unknown, the accessories market is well stocked.

Literature: Although not as well taken care of as the boxer faction, K fans don’t have to worry, because with the standard work “Fascination BMW K Series” by Axel Konigsbeck and Hans J. Schneider (published by Delius Klasing, price: 29.90 euros) you are well served.

Internet: The website www.flyingbrick.de comes across as very nice and informative. Various meetings are announced in the associated forum.

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