Kawasaki will more than likely just use an existing 400cc engine from the Ninja 400.
http://www.kawasaki-motors.com/mc/lineup/ninja400/
Kawasaki Ninja 400
399cc Parallel Twin
Bore: 68.4mm
Stroke: 54.3mm
Compression Ratio: 11：1
Power: 32kW (43hp) @9,500rpm
Torque: 44Nm (32.45lb-ft) @7,500rpm