so you went with what sounds like a 25 mph motor instead of the 30 mph motor.
Was the bike you took the motor off of a red 78?
in 78 red=25mph. yellow=30.
in the 80's they painted them different colors.
I'm still kind of wondering how a lot of gas is flowing out your muffler, when the carb is attached to the back of the crank case, with a reed valve.
Have you tried cleaning the muffler out with something?
Do you have spark? test it by holding the plug against the cooling fins while you pedal.
here is Fred's guide:
Other than that, search for PA50I and PA50II information.
I know you are 14 (according to your profile) but you need to look for information. It'll help you out more in the long run.