Vacuum Actuated Petcock valve fits on gas tank bottom on most four stroke chinese scooters. 50-150cc

Most common fuel valve or petcock valve found on GY6 engines.

If you are having gas flow problems you should look at all gas and air lines plus this valve, to check if its working and you are getting gas to engine remove main gas line from carb and try to start scooter and if gas comes out freely you are good if not replace.