Well I figure in our altitude where your clip is on the carb metering needle , if there are vacuum leaks. There are some factors. If one runs too much oil it will lean out the motor. Think of that oil having to go through that tiny orifice [venturi] on the carb. That opti is good stuff!!
Here is a mock up of the china carb by one of our Moderators. If'n you were not familiar.