Briggs and stratton 5 hp go cart runs on choke but not on run.?

i have a briggs and stratton 5 hp go cart motor. i can start it just fine, but only on choke: so i dont go anywhere. as soon as i push the lever onto run, the motor stops running. it has new gas, oil, and a new air filter... im not good with cars or motors, so if someone could put it simple and easy, that would bee great!