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Moving on to the piston now, there is lots to see and do here. First thing I noticed here was that the piston had to be made in at least two parts (possibly as many as four) that  were screwed together in order to capture the large cast iron piston ring. Next thing I noticed was how incredibly rough the outside edges of the piston face plates appeared, as seen here:

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Sadly, I was unable to get any kind of a purchase on the rims of the piston's face plates without causing damage, in order to try unscrewing them. Will likely make a clamping fixture to grip one side while I chuck the other side and may be able to unscrew it that way, the next time I have this engine apart, as there is plenty else that needs be done here, as there is much else wrong.

I did feel that since I was going to reassemble the engine right away to try and run it a little at the GPU, that I should "clean up" the rough edges around the rims of the piston's face plates and proceeded to do so chucked up in the lathe with a collet on the piston rod. However, as soon as I saw the amount of runout both in circumference, as well as laterally, I knew that something was definitely not right here, so proceeded to indicate off of the offending surfaces and found over .007" difference in the two face plate's circumferences and concentricities, but even more staggering was that there was some .040" of lateral runout. Which is to say that the faces of the plates were wobbling wildly, the meaning of which is simply explained by the fact that the hole, which was drilled and tapped through the piston assembly to mount it on the piston rod, was neither centered nor square with the surfaces of the piston's face plates! That much lateral runout means that the piston sits in the bore of the cylinder at an angle about 1 1/2 degrees off of a true 90 degrees. NOT GOOD!


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As it appeared that the piston ring was still wearing quite evenly, and no significant amount of running was expected soon, other than a short run for the GPU, I decided to defer any serious work on the piston problem until the next disassembly, when I can make a tool to take the piston itself apart, to perhaps rebore and retap and make an adapter insert, or possibly just to build a new piston. But that's for later.