In-line engine, 4-cylinder

The BMW Motorrad 4-cylinder engines which provide powerful driving force in the luxury touring bike K 1200 LT and the sports tourers K 1200 GT and K1200 RS are based on the patented "BMW Motorrad Compact Drive System". The aim of this engine concept is to provide a liquid-cooled in-line 4-cylinder engine with direct force distribution to the shaft and the lowest possible centre of gravity to ensure the agile handling characteristics of the brand. The engine also needs to be powerful, environment-friendly in terms of exhaust gas output, extremely reliable and with low maintenance. The Compact Drive System brings together these very features.

The 4-cylinder in-line engine, which draws its power from the 1172 cubic centimeters in the current K models, is installed horizontally. The cylinders are located on the left-hand side facing forwards. The crankshaft is also mounted long ways and drives the single-disc dry clutch and the six-speed gearbox by means of cogs and an intermediate shaft. The intermediate shaft also serves as a torque balancer for the crankshaft in order to compensate for unwanted tilt. The four cylinders per combustion chamber are activated via tappets by two overhead chain-driven camshafts which are supported by quintuple friction bearings. The slipper-skirt pistons are fitted with three piston rings and run in nickel-silica-carbide-coated bores which are extremely resistant to wear providing the world renowned high mileage performance of BMW motorcycles. In addition to the thermostat-controlled water-cooling system with two large radiators, the K 1200 RS and GT also have an oil cooler in the trim at the front to ensure the thermal stability of the 4-cylinder block. The oil circulation is also regulated by a thermostat.

Depending on the model, the engine delivers either 98 or 130 bhp and reaches its maximum torque of 115 Nm in the case of the K 1200 LT at 4750 rpm (K 1200 RS: 117 Nm at 6750 rpm). Due to the digital engine management system and the three-way catalytic converters, the K engine achieves exemplary exhaust emissions. The compact engine/clutch/gearbox unit is suspended in large rubber bearings so as to eliminate vibrations in the light alloy frame. The characteristic feature of the 4-cylinder in-line engine of the K models is the refined power delivery across a very broad engine speed in which adequate engine power and torque are always available. It is therefore ideal for both long distance travel and sporty riding.