I show 3 check balls in the carburetor:

One for the Power Valve Assembly Appears small to me. Another for the Inlet of the accelerator pump well which is also small in size. The last one looks bigger than the other two in my picture and it's for the Accelerator Pump discharge.

Test the accelerator pump and correct check ball placement for the accelerator pump circuit by pouring some fuel in the bowl and installing the accelerator pump in the well. Press down slowly and fuel should pump out the port and not reverse flow and go back into the fuel bowl. The accelerator pump well should also refill for the next squirt...just a little test for ya before you button it all up.

Oh yeah....the Brass "T" that holds down the spring against the discharge check ball just needs to be staked down to the bowl so it stays put. Just lightly tap the casting to swedge the "T" in place.

Joe