The concept of a 650/4 lay on the drawing boards in various conceptual stages for quite a few years until Kawasaki’s Chief Engineer Gyoichi (Ben) Inamura penned his own version, which had obvious similarities to the 900. Inamura said his brief was “to produce an enjoyable and interesting machine with a unique sports character.” And not too heavy either. To this end, every aspect of what was to become the z650 was targeted for size and mass in order to produce an ideal power-to-weight ratio. This translated as 64hp at 8,500rpm with a dry weight of 211kg.
Inside the DOHC 2-valve engine sat a forged one-piece crankshaft, running on plain bearings with two-piece plain bearing connecting rods. Instead of the gear primary drive on the 900, a HyVo chain sitting between the two centre cylinders was used, necessitating a third shaft in the transmission to drive the input side of the clutch. Valve adjustment was by shims under buckets, instead of the shim-over-bucket system on the 900 which had shown tendencies for the shims to escape. It also ran quieter. This however meant the camshaft had to be removed when adjusting valve clearances. The 650’s camshafts ran directly on
