With the engine OFF get a flashlight, remove the air cleaner and pump the throttle. Confirm that it has a good strong steady stream of fuel squirting into each primary barrel. If it does, it is not the pump. Also, make sure the pump rod from the throttle arm is connected into the hole closest to the carburetor on the pump rocker arm. That will give you the longest pump stroke. Lastly, make sure the "S" linkage connecting the pump rocker arm to the pump has the end of the "S" pointing to the driver's side. Installation the other way can cause binding.
