That's some good info...
You guys sure the squish is the same on both sides? (I mean left to right)
Leak down test it again.
Start it up with the stator cover removed...and spray carb cleaner behind the stator.
He said he checked for the crank being twisted or out of phase...
If it only, and every time deto's the left side, with different domes, different carbs, etc.
It's not electrical, it's mechanical...
It has to be crank, seal, leak, etc.