I spent a some time last night dismantling the GTC. The comment about finding crap under the wrist pin convinced me to look a bit further. Some observations so far, in no particular order:
Though I ran this engine for only about a minute myself (shut down once it settled rpm), there was enough residue on the piston (iron) to indicate the factory ran it longer. It really doesn't like running unloaded! Otherwise good condition, no problems here.
The coolant inlet port on the head had some fine sand just in the corner of the restriction.
The thick green paint is way over the top and at least the fasteners, threads and moving exterior parts will get stripped. The case is not painted inside. I haven't found any sand or other nasties in the sump, so far.
I can feel some slight backlash in the idler gear if I really pay attention; just by feel, I'd guess the flywheel moves about 1-2 degrees. Seems normal but I could check more accurately if someone says otherwise.
Fuel lines have teflon tape on the threads, and the flared ends look like they were 'polished' with 80 grit paper. Governor linkage is sloppy through the bellcrank and pins.
Oil pump works, though I will dismantle it also. The oil dipper is 1/4 turn out.
There are 4 thin paper shims under the jug, no 1/2 gaskets.
I will report further findings when I have a chance to putter with it again. This engine has a 7 stud head, no liner, and iron piston.
P.S: What does the 'K' stand for on the small rotating cover near the bottom of the crankcase (opposite side of filler and dipstick? It says 'Oil K'.