Kawasaki is still developing the horizontal-cylinder engine, this time filing patents for a 90° cylinder as opposed to the 60° cylinder that we wrote about last year. This revision adds a stacked gearbox, which adds increased swingarm length to the long list of benefits such an arrangement would bring.
Performance advantages of this engine layout include reduced weight and
reduced size thanks to combining the block with the transmission
housing, increased stability thanks to the gyroscopic effect of the
crankshaft being moved closer to that CG and increased perceived
smoothness because of the change in prevailing vibration angle. There’s
also advantages to the intake system thanks to a simplified route for
pressurized air. The decreased overall height of the engine allows a
so-equipped bike to be radically repackaged, the center of gravity
could either be lowered or raised depending on which handling
characteristics were appropriate for the machine in question.
The horizontal-cylinder engine is already used in bikes like the
Husaberg FS 570 Supermoto, where it reduces the tendency for the
motorcycle to upright itself under power and increases the ground
clearance in addition to allowing for a straighter path between airbox
and cylinder. This setup differs from the reversed-cylinder engine of
the 2010 Yamaha YZ450F in that the exhaust and inlet ports are still
conventionally located on the front and rear of the engine.
In the past, Kawasaki has patented the horizontal-cylinder engine for
use in a variety of machines — ranging from quads, to dirt bikes to
supersports — meaning it could be looking to employ such an arrangement
across its model range, lending its products a clear mechanical
differentiation from their too-similar Japanese competition.
Image via MCN