Originally Posted by TommyK
Check for vacuum leaks. If none found the next culprit would be an excessively lean idle setting.
Thanks! It was a lean condition. I tightened up the two mixture screws, and then turned them out 5 turns, counter-clockwise. The engine was still a bit shaky, so I did one more full turn on each one, and that did the trick.
The engine now starts up at 1500 rpm (vs 1000 rpm)
, and drops to a smooth 750 rpm (vs barely 500 rpm)
The transmission no longer shifts with a super-loud clunk. (It still clunks a bit, but it has always done that since I bought it a year and a half ago.)