cyrusb,
the piston never got my attention. After purchasing the bike in Las Vegas and riding it to Tucson, it died at the end of the trip. (It became progressively harder to start during the course of the drive).
Compression was 30psi. When I took of the head to find out why, I found the head and cylinder were extremely carbonized. I took the head and piston and cylinder into a machine shop for measurement, and they reported there was .006 gap between piston and cylinder; the manual says new is .002, .008 is extreme wear and needs replaceement.
The piston was never a problem. The valves weren't closing properly due to the carbonization, hence the low compression.
Turns out the carb jet setting was for max richness, and there was rust in the tank. I assume as the previous owner found it running poorly, he kept enriching the mixture.
With new valves and a clean head, I'm hoping the piston wear will not be too excessive and the bike should be operable. I'll let you all know!