Carburetor diaphragm for 50cc GY6 139QMB engines. The carburetor diaphragm is located in the vacuum chamber on the top of the carburetor. A broken or damaged carburetor diaphragm will keep your scooter from accelerating properly. It may idle fine but your scooter will be sluggish when you give it some throttle.
An extra carburetor diaphragm is a good thing to have in your spare parts box for your Chinese built 50cc GY6 139QMB engine.