The kick starter knuckle is threaded on one side only. This is so it can clamp slightly as it is tightened.
The bolt need not be anything special, but I would use a high tensile bolt if possible.
And yes, the bolt positions on the cut-away part of the spline. This sets how far on the spline the knuckle sits.
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[color=#808080][size=9]Yes,.. I too know how to waste Time and Money,...