2012 KAWASAKI Ninja ZX-6R, Pound for Pound, the Mightiest Middleweight Sportbike in History Technological tour de force. That s the only way to describe the original Ninja. 600 sportbike of 1985. Packing a liquid-cooled 16-valve inline-four (the first ever in a middleweight streetbike), wraparound twin-spar frame, anti-dive fork and aesthetics snatched right from the Grand Prix circuit, the original ZX600-A1 was a dominant, bigger-than-life middleweight. Apparently, some things never change.