I'll add some pics soon but let's just move on.
The pulley...
I'll give my details but you'll find almost identical issues in all vertical shaft engines.
they are a 1" shaft (25.4mm) and have a keyway (we'll get to that spec soon)
Then onto a pulley hub.
Typically the upper hub is for drive and the lower is the "PTO" or power take off which drives the blades assembly.

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R. Pirsig .