Danno,
So, After all my new gaskets arrived, I did a wet compression test:
2 ml of Valvoline 20W50 full synthetic motorcycle oil in each cylinder via a syringe and a rubber hose (right at the edge of the piston)
Rotate with 14mm socket by hand through a few rotations.
Compression test each cylinder open throttle.
Both went up to 125 psi - exactly.
This bike only has 20,400 miles and I know the owner for its entire previous life. He says he was very good about oil changes. There's no way the bores / ring / pistons are THAT worn. I'm thinking the rings are stuck from sitting.
Thoughts?
I'm going to try the piston ring soak method you outlined here:
https://www.ninjette.org/forums/showthread.php?t=343925
It's not looking too much like a head gasket or valves anymore. I guess only a leak-down test would tell.