All of the Z50 mini bikes share the same engine family as the CT70 and the CT90. The only difference in the CT70 and the Z50 motor is the smaller bore cylinder. The Z50 did not have the neutral switch either, just as the earlier CT70 engine. Almost all the parts, except the head and the cylinder are interchangeable with the CT70 engine.
The Z50 carburetor is different with a smaller intake.
Click on the pictures below to see the different parts restoration.