It needs tension to move normal. If the carb is close to where it belongs it don't work.If I understand this correctly- with the carb bolted in place- the throttle plate does not move and appears jammed in place- but with the carb removed, the throttle plate moves in full articulation as per normal?
Where is the gasket meant for between carb body and plastic intake block?
The gasket may space the carb back enough that the throttle plate does not catch and bind on the throat of the intake block.