Yeah.

Things I have NOT done:

taken the diaphragm side of the carb apart to see if the diaphragm has a tear or pinhole (How would I find a pinhole without destroying it, and would it run at all if the diaphragm was torn/pinholed?

tried a different spark plug--don't think it's the problem, the couple of times I've gotten good rpms, it was fine

tried a different ignition module (don't have one to try)

Even at 50:1 oil mix, I still get a LOT of black goo out the exhaust. I'm almost inclined to think that this Amsoil Saber is made for a much leaner mix than even 50:1. The bottle says 100:1, but I didn't want to try it that lean until I had the engine running well and broken in. I can't see that the Fuji oil is any better than Amsoil or Klotz and I can't find it anyway.

Any other suggestions, before I have to remove the engine and ship it back?