Does anyone know how to change the opening

remove the top of the carburator, compress the spring on the jet, you will see the end of the throttle cable, unhook it from the holder, unthread the top of the cable from the carburator, pull the cable out. Now it is disconnected from the carburator, now disconnect from the throttle handle by removing the the two screws on the handle, unscrew the adjustment, then detach the cable. Replace in repeat order.