I hadn't even got to doing a plug chop yet. This was it's first voyage with the new carb. I did let it get up to temp before letting him take it for a spin. Did not seem to be running to hot and the exhaust seemed fairly rich. So I wasn't too worried about seizing her up. I'm hoping it is only top end. I'll pull the head once I've allotted myself the appropriate grieving time and quit being angry about it. From the sound of it, if the rings are shot, it certainly sounds like pieces of them may have made it down into the crank.