According to page 22 of the owners manual this can mean two things:
- The choke is opened to soon. If so move the choke to the halfway position until the engine runs smoothly; or
- The carburetor is out of adjustement. Contact your local service dealer especially since its brand new.
When you say the automatic choke I have a hunch you actually mean the governor or automatic throttle. This controls the engine so it only runs at top speed when the generator is underload. Its a fuel saving feature.
Page 7 also says to start the engine with no load, wait for it to come stabilize and then add loads. Make sure the devices are "Off" before adding or removing them from the circuit.