Bogs, you are right, but as I have tested throat sizes from 0.6 mm to 1.9mm, there doesn't seem to be any sweet spot.
Too small throat size causes flooding, no matter what; with ~1.2-1.9mm throat, the engine starts easier, but runs too fast.
Maybe the compression ratio is too high; at the beginning of this project, I was going to make a cylinder head, that allows the comp ratio to be adjusted.
Back then, it did seem too complex thing to achieve. Not impossible anyway.
Lowering the comp ratio is just one of the options to test.
But in the mean time, I'll assemble the engine.: