The crankcase started life as a 125mm diameter by 300mm piece of Aluminum 7075-T6. I bought a stick of this long enough to make the front cover, crankcase, rear seal plate, air guide, impeller, and a few fixtures. The diameter was needed to accommodate the crankcase so I did end up wasting a little material on the other parts. To make the crankcase, I sawed off a 4.75″ section so I could move everything closer to the chuck.
I’ve combined the cylinder studs and the valve adjusters on one page because they are practically the same thing. I bought one box of #4-40×3/4″ 18-8 stainless set screws from McMaster-Carr (P/N 92311A113). For the cylinder studs, the socket end was cut off and rounded. For the valve adjusters, the cup end was cut off and rounded.
Finding high quality materials here in China is a problem so I’m always looking outside-the-box to find materials for my parts. For these tappets, I ended up killing three birds with one stone. By using some hardened dowel pins from McMaster-Carr, I ended up with quality steel, a ground surface finish to ride against the bronze tappet bushings, and a hard material to ride against the cam ring.