An interesting discussion for me as I own 1979 versions of both the CBX and KZ1300. I've read the opinions of 2 authors and have heard the comments of another collector who all, like myself, own both bikes. All four of us would sell the CBX before we'd get rid of our KZ1300's. My reason is that I enjoy relatively high speed 200 to 400 mile runs with a standard bike's upright riding position (easier on my back) and the KZ1300, as such, is unmatched for riding comfort and stability (especially in windy areas) by anything else I've experienced.
I'm very fond of both bikes, but rarely see in print their two most important pieces of info. In 1980, Kawasaki had to increase the engine oil capacity of the big KZ by approx. 40% as riders were burning up engines. So watch the oil level in 79 KZs! The CBX, if left in the sun on its side stand, may create gas fumes in its high side cylinders (six carbs) that, on ignition, can blow out the top end of the engine.
My bikes are both basically stock (yes, original exhaust pipes) due to my interest in the history of motorcycling. However, the CBX is blueprinted, has the Hondaline fork brace, & steelbraded break lines. In reference to Easytarget's comment, I enjoyed riding an 1985 version of the GPz900R for many years (mine was originally a Canadian bike) and found that, like the CBX, it felt much lighter than it you might imagine.
In comparison, the CBX/KZ1300 are very different bikes. In 1979 the CBX was a pure sports bike with better acceleration and cornering and is very easy to ride. The big KZ is, in a number of ways, a handful to ride and has bad cornering ground clearance but a slight top end edge on the CBX and is a very comfortable high speed tourer in the tradition of Kawasaki high performance sports tourers.
