Pour a little gas in the spark plug hole, if it fires and quits then it’s a fuel flow problem. Did you hook up the lines on the pump wrong? Did you wire tie all the connections? You could have dirt, did you clean the carb or at least check the screen under the fuel inlet?
FAA certified jet engine and aircraft technician,
Nicholson Speedway class champion 2001,
Yamaha KT100 Service Center,
41 years karting experience