One damned thing after another..., Ping of Death Options

[lapuwali]

Finally get around to fixing a pulled exhaust stud, get everything buttoned up, quick test drive. Back into the garage, check all of the exhaust nuts. Long test drive.

Runs OK for about half distance, then it sounds and feels like it's losing a cylinder. Thudding exhaust note and no power. Up a steep (unavoidable) hill, it starts what sounds like really loud ping under load. Goes away when I get off it, and stays away if I keep the speed down up the hill. CHT on No. 3 isn't higher than usual (about 340 up that hill, about 300 on the flat). Nearer the house, it idles OK, but doesn't pull away from a stop w/o a fair amount of clutch slip. No odd noises.

Sigh.

Haven't the time to pull everything apart to take a good look this weekend. This engine has been trouble from the word go. I've had maybe 50 trouble-free miles in the last 6 months.

I'm beginning to think a Soob conversion isn't an option, but a requirement. No way I'm going to spend serious money on this engine...