Watch a video about how the accelerator pump circuit works, including how to test your accelerator pump.
https://youtu.be/5VJH9KYyjEs?si=l1eM_e6MH2aOY4gB
This is where the fuel comes out when stepping on the gas. Some YH carbs use a check ball (the bigger steel) and a spring (you can use a 2nd check ball in place of the spring) and others use a check weight only.
