RE: YS 140L inverted
I think the regulator is too rich. The reason why it is not running poorly at that setting is because with the engine inverted, the excess fuel is dripping out rather than being ingested into the air flow. If the engine were upright, that excess fuel would be entering the engine and causing it to overload. I would continue to lean the regulator a little at a time until the dripping stops. Remember to reset the the high end needle each time. If this doesn't stop the dripping, there is likely something foreign in the regulator.
Blessings, Terry