I’ve mentioned before that obtaining quality material is one of my biggest problems here in China. Well, a corollary to that is that when I do have material, it’s probably not in the easiest-to-use form. For the jackshaft, I used a drop from a piece of 416 stainless plate that had been hardened to Rc35.
Many of the gears used in this engine need to be re-bored to a larger shaft size. There are drawings in the plans for holding fixtures to do this, but I found it easier just to use standard collets. This should also do a better job of maintaining concentricity between the bore and the gear O.D.