The Gasket & Metering Diaphram cannot be upside down , it will cause your flooding and its important also that you set the inlet control lever correctly or the engine will flood easilt not to mention a worn out metering diaphram.
Here is some good info that addresses those point l mentioned , hope it helps you resolve the issue your having.
Some of us fellas also do a Needle pop-off test on the carb ,
To help you out with the Oem parts here is a new Metering Dia and gasket. PM me your address and l will put in mail to forward to you.