It looks as though there might be some tension on your throttle cable below the clamp which would require a heavier return spring to bring it back to idle. I would first disconnect the cable and try it to see if it helps but then reinstall it with the end of the cable at the clamp and only the inner wire extending down to the rod in better alignment. If the wire isn't long enough to reach this way you can cut the cable shorter by pulling the wire back inside of the cable and then cut the cable which will allow for more wire to be exposed
