I currently have a '84 KZ700. To make a long story short the motor is toast and I cannot find oversize pistons readily. I found a 750 motor from about the same year and I am wondering if the 2 are interchangeable. I know they dropped to a 700 trying to get around additional import taxes, but I find it hard to beleve they redesigned the whole motor. My thinking is they just decreased the bore and maybe the stroke also to lower the displacement. I would think the cases would bolt right into my frame and the clutch and rotor from my old motor would work. I plan on using a stage 3 kit for the carbs which would give me the additional fuel needed between larger displacement and 4-1 header. Anyone know for sure on this???

:991

Don't know for sure, but I would have to agree with you - Big K would not re-design the whole motor for such a small change in capacity.
If you look at the way Big K have developed engines - its as a "family". By that I mean the GPZ900 motor was brand new - water cooled etc. It gave rise to the old ZX10 egine, GTR1000 engine ZL1000 engine then the ZZR1100 egine. Even the "new" z1000 has its ancestry in the GPZ9's genes.
Hope this helps.
Vin