BMW Media Information 10/2010 page 14
side. Precisely where the greatest thermal stress occurs, the intensive cooling at the cylinder head ensures rapid heat dissipation and therefore an excellent temperature balance. The diminished water flow at the cylinders reduces the warm-up phase and restricts cold-running wear-and-tear and friction, which also benefits fuel consumption. The coolant volume (50 % water, 50 % nitrite-free antifreeze) is 3.5 litres including 0.5 litres of levelling volume. The water pump and the oil pump are powered by the primary drive via cogwheels. The radiator is trapezoid and curved in shape and housed in the trim at the bottom front to optimise the centre of gravity. Due to the minimised frictional loss of the engine, the high degree of efficiency and the sophisticated aerodynamic design of trim and air flow, a comparatively small area of just 920 cc is sufficient for reliable heat dissipation in all conditions. The integrated thermostat keeps warm-up times as short as possible. Ancillary units - alternator and starter. In order to save construction space the electrical ancillary units and their drive mechanisms were moved behind the crankshaft into the free space above the gearbox. The three-phase generator is driven by the primary toothing of the clutch. The rated output of the generator is 580 watts, with a peak current of 57.5 ampere. With a view to optimising power consumption, the gear ratio of the crankshaft to the generate was fixed at 1:2.0. The reduction-gear starter is linked via a one-way clutch which acts on the generator drive gear.
Power transmission: narrow three-shaft transmission and selfenergising clutch. Torque is transmitted from the crankshaft to a 10-disc wet clutch via a straight-toothed primary drive. Here the developers paid particular attention to a low level of control force at the hand lever. This is achieved by means of a self-energising mechanism in the clutch cage. When this is active, it may cause slight movements in the clutch lever. The gearbox complete with bevel gear is integrated in the engine casing. In order to reduce construction width in the area of the rider footrests in