• Hesitation can be caused by the distributor advance not advancing, which I will not be addressing here.

Incorrect check ball placement.

The smaller (may be aluminum) check ball goes at the bottom of the pump well, or on some models the hole next to the pump well.

Watch a video about testing the accelerator pump:

https://youtu.be/bb_m4c3xS7A?si=i4mBFYvTqmghzO9u

Inlet Check

This is where the gas feeds into the Rochester B accelerator pump well. It can be located at the bottom of the pump well, or on some models next to the pump well on the bottom of the float bowl. To test this, fill the bowl with mineral spirits and place the pump into the well all the way down. Pulling up the pump should fill the pump well. If not, then the inlet check may be stuck, or the passage could be plugged. Check a passage by spraying carb cleaner into the passage to see if it exits.

Main Discharge

This is where the gas comes out when pressing on the accelerator. With the float bowl full check the discharge by pressing down on the accelerator. Looking down the carburetor you should see a squirt of gas. When starting cold press the accelerator once. This allows the choke to close (hot air choke) and it squirts extra gas into the intake needed for a cold start.

• When there is no squirt:
  • Be sure the larger check ball is in the Rochester B main discharge hole and there is a spring above it along with a T to hold it down. You can tap the check ball gently to help it form a good seal.
  • Clean out the small passage in the tube that goes across the inside of the carburetor throat about half way down. You can try spray carb cleaner sprayed into the hole. Fuel will squirt from here when the accelerator is pressed.
  • The passage from the accelerator pump well to the main discharge may be plugged. Blow air through it to check. You can also put some fluid in the pump well, then press down on the accelerator pump. Fluid should come out of the main discharge.
• Put some fluid in the pump well and press down on the pump. Fluid should come out of the main discharge hole.
• The main discharge uses the biggest steel ball, then the spring, then the T.

Carburetor pops when stepping on the gas.

Pump sticks

With the sticking pump, I would look there 1st.

Was the original pump a round stem pump with a leather cup? If that was the case, then you should have replaced the entire pump. You can't replace the leather with a rubber cup.

Apply 2 drops of white lithium grease to the rubber cup.