There are 2 possible clutch mounting types:
Outboard mount, meaning clutch sprocket can only be mounted facing away from engine block. This type is secured to pto with a single bolt (typically 5/16x24) and washer via internal threads (usually has built in key).
The other type will mount inboard or outboard (sprocket toward or away from block) and uses set screws to hold it onto shaft.
I prefer the inboard/outboard type as I sometimes swap engines from mini bike to kart.
Kart is mounted outboard. Mini bike is mounted inboard. They are also movable (slightly) in or out for chain alignment.