BMW K 1300 GT - Manual (Page 10)

BMW
Media
Information
10/2008
Page 10
model, drives two balance shafts positioned symmetrically in front of and
behind the crankshaft via a gear drive, achieving a balance of no less than
86 per cent.
The balance shafts turn twice as fast as the crankshaft. To minimise any noise
or sound waves generated in the process, the balance weights are connected
to the balance shafts by means of elastomer units.
Extra-stiff cylinder/crankcase unit.
Split horizontally along the middle of the crankshaft, the cylinder crankcase
is made of a high-strength aluminium alloy. Made of a die-casting, the
compact upper section forms an extra-stiff composite unit comprising the
four cylinders and the upper bearing support for the crankshaft. The cylinder
block together with the coolant sleeve is an open-deck construction and the
cylinder liners come with a wear-proof, low-friction nickel-silicon dispersion
coating. Made as a pressure casting, the lower section forms the counterpart
to the main bearing on the crankshaft and takes up the gearbox, holding it in
position.
Cylinder head and valve drive upgraded to an even higher standard.
The power and performance qualities and characteristics, the quality of the
combustion process and, accordingly, the fuel consumption of a power
unit depend to a large extent on the cylinder head and valve drive. Hence, the
four-valve cylinder head of the K 1300 S is designed for optimum duct and
fl ow geometry, compact dimensions, optimum thermodynamics and a reliable
thermal balance. The tight valve angle provides an ideal, straight intake duct
and keeps the combustion chamber extra-compact for high compression and
optimum effi ciency.
Seeking to achieve optimum output and superior running stability also at high
speeds, and at the same time ensuring superior stiffness, keeping all moving
masses to a minimum and optimising the timing overlap on the valves, the
K 1300 S, like its predecessor, the K 1200 S, comes with drag lever control
on two overhead camshafts. This offers the perfect combination of maximum
stiffness and minimum weight of all moving parts in the valve drive, at the
same time keeping the cylinder head as compact as possible.
As on the former model, the valve angle is 10° on the intake and 11° on
the exhaust side – fi gures unparalleled to this day by any other engine in this
market segment.