I did check the head/block seal. At first, I could see a little bit of fuel leaking out from the top of the block, and noticed that the head was on a slight angle... I took it inside, inspected everything, piston, etc looked OK, so I re-bolted the head in the "X" pattern, and it seems sealed.

Inspected it once I had it running, and no fuel leak anymore.

I'm running byrons 20% which is the recommended fuel for this engine...

Odd part is that it's running PIG rich, and still getting crazy hot! I mean, at idle, I've got a crazy amount of exhaust smoke, and it's got that pig-rich idle sound...