It sounds like the throttle cable is not routed correctly. Specificly in the carburator where it attaches to the slide in the carburator. Take the top of the carburator off. The two screws where the cable goes in. After undoing those screws the top will come off and the slide will come out too. There is a spring between the top of the carburator and the top of the slide. The cable either goes around the spring or through the center, I forget which one. But if it is the wrong way then the choke will not disengage, it is currently installed the wrong way.
Been there done that.