If the primer bulb will not not pop back out there is a blockage in the fuel supply system.
Fix it first before you go playing with things.
Try it without the fuel line collected to the carb, then with the return line removed from the primer.
If it is a remote primer try with the carb disconnected from the primer bulb.
Lots of different set ups some with only 1 check valve some with multiple check valves.
Also make sure the primer is connected correctly if it is a remote one & not hooked up backwards.