So what is it? It's not a "Z1" type head, yet it doesn't have screw in cam caps.
There are two different KZ1000 engines. The first is the Z1 type which was built between 1976 and 1980. The second is the 1000J, or "J model" as it is called, and was built from 1981 until present ( currently only available in police motorcycles). These engines are different, but some of the parts can be interchanged, and this has caused much confusion. We hope this makes everything clearer.
Cylinder head.. J model head has larger valves and ports. This head can be used on earlier style cylinder and lower end by installing APE #CCIA cam chain sprocket adapter in head . How to tell which head you have.. Early style heads have four factory drilled and tapped 6mm holes in the center to bolt in cam chain idler gear. Z1 900 heads have 6 mm exhaust studs, KZ1000 8 mm. On the J model head, the four cam plugs at the ends of the camshaft areas are bolted in, on the early style head, they just push in and the valve cover holds them in. The J model / '81-'82 GPZ1100 cylinder head has a larger combustion chamber than the early style head. When these heads are used on the early style motor, a compression ratio drop of about 2 full points can be expected.
