I'm thinking fuel pump:

[oldkid]

Fuel pump FYI. My 150cc would not run long at WOT when new because of lack of fuel. Sometimes I had to reduce to about 80% to get up the TN hills. I added a low pressure electric pump and pressure regulator and no more problems. Runs much better now. My pump only had power if switch is on. In addition I use a toggle switch to turn off pump when I want the carb. empty for storage.