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Single-cylinder engine

Single-cylinder motorcycles are generally regarded as the original form of two-wheel transportation. The BMW F650 models and the G 650 X series follow the principle of "less is more". Their trademark is the robust, water-cooled single-cylinder 4-stroke engine. With its uncomplicated structure, powerful torque and superb running smoothness, it is predestined for use in light enduro motorcycles - i.e. in bikes which offer excellent performance both on and off the road. Its low fuel consumption also results in reduced running costs for this entry-level category.

The liquid-cooled single-cylinder 4-stroke engine with 652 cubic centimetres has a crankshaft made of separately compressed components which rotates within friction bearings in the vertically separable housing. The connecting rod also has friction bearings, its lower eye being non-divided. As with all engines in the BMW Motorrad range, the slipper-skirt piston runs in a nickel-silica-carbide-coated bore which ensures minimal wear-and-tear and thus high mileage. In order to compensate for strong forces of inertia, a balance shaft powered by spur gears rotates the other way to the crankshaft. It is positioned at the front of the engine casing in front of the crankshaft and drives the water pump itself.

In order to achieve maximum clearance for off-road riding, dry sump lubrication aids oil distribution. The modern cylinder head with 4-valve technology houses two overhead camshafts which have a direct effect on the valve shafts by using tappets. A roller chain with hydraulic chain tensioner provides the linkage between the crankshaft and camshafts.

The single-cylinder engine draws the fuel-air mixture from a fuel injection system. The injection is controlled and monitored electronically. This also ensures that the three-way closed-loop catalytic converter in the tailpipe provides optimum cleansing of exhaust gases. The single-cylinder engine with up to 50 bhp - also available in a power-reduced 34 bhp version for those new to motorcycling - propels its power by means of a multiplate wet clutch to a constant mesh five-speed gearbox.
The motorcycle press confirms in all cases that the BMW single-cylinder models have particularly low vibration levels and powerful torque thanks to this engine concept.