Motor runs wide open but no power from generator

Question

Powerback
10 Hp Tecumseh
Model # gt5250-2

Neighbor left this gen under his deck for 4 years covered. Motor runs after new carb. When I start the motor up it goes to maxium rpm but get nothing from the generator. Governor is wide open on the motor, and i can control it by pushing on it. Its like its being told give me all you got. But still no juice. Thank You Angel Starr