TOPIC:

650 for the 'classic' Z shape. Mk11 is the next 'classic' Z shape. 750's are a cross over between the two and dont quite work to my mind.
Never ridden a 750 so cant comment on performance.

In 1974 I bought a 900z1 Rode it for a few years and sold it and moved to Arizona and kicked myself for ever letting it go. Got a chance to get a 1976 Kz900 and I grabbed it quick a few years ago. Not as Quick as the newer stuff but plenty fast enough to scare hell out of this old man if I'm not careful. A dedicated rider is so for life.

Well the title says "KZ", but your short list doesn't have what I have. In 1975 I bought a new Z1B and absolutely loved that bike. Sold it a few years later and regretted ever doing so. Life took me away from my desire to buy another mid '70's Kawasaki. Many years later either my wife lost her mind, or got sick of hearing me talk about buying another Kawasaaki and she gave me the go-ahead....... Bless Her Little Heart. So the hunt was on, but I soon discovered the 900's were a bit too expensive for my taste. I ended up buying a '77 KZ-1000A1 (not cheap either) and went through it. From a personal standpoint point I think the early 900's and KZ-1000's have a look about them that screams KAWASAKI! They simply cannot be confused with any other motorcycle then or now. I am sometimes amazed when I am out on my KZ at how many people recognize it and ask me if I want to sell it. Perhaps one day I will say yes to one of these prospectors, but they better bring a fat wallet. One last note is that I opted for the '77 because it had a rear disc brake and I am a big fan of them.
Rick H.