earlwb

Well, you will need to remove the flywheel and switch to electronic ignition instead. It is easy to get CDI ignition modules from many sources. The owners for some conversions made a flywall mounting plate to affix the engine with off the back where the flywheel used to be.

Then you need a prop hub to mount the propeller off the other end of the crankshaft. There is a slot for a woodruff key. The center bolt is used to help keep the hub on and you use four outer bolts to mount the propeller onto it.

The CDI ignition magnet goes into a hole you drill into the prop hub for that purpose. The hall effect sensor uses the magnet to fire the ignition coil.

What you do is use a lathe to make the prop hub. It is a relatively snug fit onto the crankshaft. But you don't bore the hole all the way through. You leave a shoulder or step so that the center bolt is used to keep it on tight with. The tricky part is cutting the woodruff key slot. You can't use a broach as the bored hole doesn't go all the way through. You need to take a lathe cutting tool and grind it to size. Then you lock the hub in place on the lathe and run the tool in and out shaving off slivers of metal until the groove is cut to about the right depth. I would go for a snug fit where you need to heat the hub up good so it expands and then slip it onto the crankshaft end (along with the woodruff key). Then put the center bolt in to help keep it on. Before you mount the prop hub, of course, you need to put in the four mounting screws for the propeller too.