i figured out the issue... evidently with as often as the exhaust studs kept coming loose, one of the times that it came completely off, a washer bounced back through the exhaust port into the cylinder... got caught up in the rings... carved a trench in the cylinder wall, welded itself into the rings and broke them both... replaced the cylinder, dug out the rings and replaced them, cleaned up the piston, put it all back together and it started right up!