Thanks so much for your follow up.
My motor as pictured looks just like yours. I have installed the magneto and put what looks like a set screw into the notch on the crankshaft collar.
I also put some tension on the screw that compresses the collar – but not enough to bind it. Hard to believe this screw remains in the same position after the engine has been running.
All appears to be well. I should be doing a test start soon. Any tips on the fuel/oil mix will be welcomed.
Thanks again.