Be careful taking it apart. The pictures show more than one replaced machine bolt.

But I wouldn't run it or even turn it over by hand before oiling it. And let it sit for awhile with the oil in it.

The replaced bolt on the backplate appears to be loose. Don't run it before checking it out closely.

Those red-head McCoy engines were somewhat short lived in their day. They didn't have the toughest piston/sleeve combination. If you ever ran it lean, it needed a rebuild. Back then more than half the flyers commonly rebuilt engines. Guys would have the parts (piston/sleeve, conrod, wrist pin, gaskets) like people today have extra props. And they usually got their training when they ran their first McCoy.

At one time, they marketed McCoys in blister packs. They were an excellent deal for guys who knew how to keep them alive. But they usually didn't win any contests.