Quote Originally Posted by daruby View Post

Replating and machining the piston after replating is not the hard part. The hard part is boring and honing the cylinder (with the large holes all around it) and ending up with a perfectly round and straight sided cylinder, and THEN getting a replated piston to fit with just the right tolerances. I had a long conversation with Paul Riggett on this topic when his techs were working with York in Markneukirchen from about 2007-2009 on trying to get their valve production under control. They never really did and it is not un-common for York valves to not be able to "spin" in the bore or have adverse wear. According to Paul, you have to know how to compensate for what happens with the boreing tools as it passes through the ports where there is no material on one side and yet is cutting material on the other side.
Some really interesting insight, Doug, thank you for sharing! I had a lesson with Steven Mead a few years ago (when I was still playing on a York Preference euph) and he mentioned how the valves on York instruments could sometimes have issues. I guess that's probably what he was referring to.