Parts such as the Kick Starter: Circlip, Ball (12r), Kick Crank Assy, Gear, Kick are included in the Mx100 1980 (a) Usa Kick Starter parts fiche.
With two applications this Shim, Main Axle 0.5mm is the most specified part.
The Ball (12r) is the cheapest item from this partsfiche.