I also worked on the main crankshaft center bearing. Fairly straight forward lathe work. I started with a couple of bronze bushes and machined a bit more than 1/2 off of each, then soldered them together.
I chucked them up in the lathe and drilled and reamed the inside diameter to .501″, then turned down the outside diameter to .625″. I made a little sideways notch tool and machined a small groove in the middle of the bronze bearing for oil. Then cut it off.
For the bearing caps, I grabbed a couple of pieces of scrap aluminum, fly cut a smooth surface on each. Then clamped them together in the vise. One was a tiny smaller so I used a few pieces of paper between it and the vise jaws to lock them both down. then I machined a couple of countersinks, drilled and tapped, then screwed them together.
then back to the lathe:
I turned the outside to 1.250″ and drilled and bored the inside diameter to .625 using the bronze bushing (still soldered together) as a check. Faced the outside, cleaned up the edges and parted it off.
I then heated up the bronze bushing and separated the two halves.
Below is the bearing cap and the bronze bush installed in the upper crankcase.
I oiled up the bushing and tightened everything down. there is an area of about 10 degrees where the crank is a bit tight. I’ll inspect it and see if anything stands out, otherwise I think this will wear in. I still need to drill the oil hole in the cap and bronze bushing and I will also drill a small hole and inset a brass taper pin to insure the bronze bushing does not spin.