Near as I can tell there is no oil pressure spec that means anything at the carbs. The oil gets metered into the fuel chamber inside the VRO2, so all the four throats ever see is fuel pressure. Fuel side sits around 3 to 5 psi. The fuel only replacement pumps are rated 3 psi and up.
So the bypass test needs very little. Squeeze the bulb hard and hold it while someone cranks. If it fires and keeps running, the pump is your problem. No electric pump needed for that. If you do plumb one in, keep it low, 2.5 to 4 psi. A high pressure EFI pump will push past the float needles.
Before buying anything though. It runs on ether and then dies, so you have spark and compression. Check the pulse hose to the pump first. The fuel side runs off crankcase pulses through that small hose, and on these loopers a cracked or gas soaked pulse hose is common. If it smells of gas inside, the diaphragm is done.
I would also look at the electric primer. Cold start enrichment on your motor is that little solenoid on the intake with the red lever, not a choke plate. If the lever got bumped to manual, or it does not click when you push the key in, it will do exactly what you describe. Pull its outlet hose and crank, it should squirt. Crack the float bowl drains too. Dry bowls and fuel is not arriving.
One caution on the bypass. When the oil lines come off, cap the nipples on the intake. Leave them open and you have a vacuum leak. FWIW I would try the bulb before buying any parts. thanks
