As we have discussed here many times before, the regulator controls the transition between idle and full throttle. The starting point for the regulator screw is with the top of the screw flush with the top of the regulator body.
From that point you will either lean or richen the transition by rotating the screw either clockwise to lean and vice versa.
If you are losing a large amount of fuel into the carb with the tank pressured up, the plunger is not sealing, either due to debris, damage or improper assembly.

Did you completely dis-assemble the regulator and did you re-install it on the engine correctly? the bump on the casting faces to the front of the engine.