The Z50 only used the 3 speed Auto Clutch. The Z50 Clutch is exactly the same and interchangeable with the CT70 3 speed Auto Clutch.
There are two types of CT70 auto clutches. The earlier type uses only two friction disks, and can be identified by a big circlip holding the clutch gear. The later type uses three friction disks. Both types of clutches operate exactly the same and are interchangeable.
The procedure for rebuilding is exactly the same for both types of clutches.
CT90 Uses auto clutch only. There are some minor differences between the CT70/Z50, and the CT90 Auto Clutch, the procedure is essentially the same as described below.