I ran mine with 90 psi just fine for a while, everyone swore that was the lowest it would run. Was that warm or cold?
I've heard horror stories of the crank seals going out on these. I think that would cause case compression loss after being warm. Have you got the tools to do a leak down test?
Is personally would dodge that, just just because I wouldn't want to know. I would be cleaning the carb, everything down to plug wire. Actually, just a wild shot, have you trimmed the ends of your plug wire? I chased around all issue not long after getting mine, did everything, just to find that the ends of my wire were very worn.
Probably not it, but I'm just grasping at straws.