I bought a NOS genuine Kawasaki back mag wheel for my thou A1 from flea bay and, like the mug I am, had a tyre fitted before checking that the cush drive sprocket fitting would be the same

.
The wheels it currently has are aftermarket, presumeably sourced from Italy from where the bike was imported. I assumed, wrongly it seems, that the cush drive/sprocket fitting would be the same regardless of wheel.
Anyone got any bight ideas?
Many thanks
Ralph Ferrand
Z1000A1 (1977), Z1300A5 (1983), Z900A4 (1976) GPZ1100 Unitrak (1983)(project), RD250B (1975)(project), ZRX1200R (2005) DT175MX (1981) YZF R6 (1999)
http://www.bikerstoolbox.co.uk