The Walbro carb does have a fuel pump, but that pump is powered by a air-pulse-driven pump diaphragm. That pulse comes from a pressure tap (tube) running from the crankcase to the carb. The pressure wave comes from the piston moving up & down. 2 stoke crankcases possess a really nice pressure pulse, and 4-strokes are fairly good enough to work (note there is a breather tap). But the crankcase on a radial has a very poor pressure wave due to it's large size and very gradual progressive piston transitions.

Someone on here suggested an electric fuel pump to run the walbro. I could be wrong, but it seems to me you cannot just hook up an electric fuel pump to the fuel inlet on a walbro and expect it to work. Remember, when filling your gas tank with an electric filling pump how the gas doesn't come gushing out the walbro like it does a glow carb? (true with a simple filling tee in the fuel line running from the clunk to the walbro, than you plug after filling). The gas doesn't gush out because the pump diaphragm's reed valve is stopping the fuel. It must be pulsing to allow the fuel through.

For the electric pump mod, even if one poked a pin hole through the reed valve to let the gas through to the regulator side of a walbro, the electric pump is much higher volume than the walbro consumes, so that will lead to unpredictable fuel mix issues. The Walbro regulator has a pop-off spring valve that will pass fuel through unrestricted if the input pressure gets too high, like 10-15 psi if I remember. An electric pump can easily achieve this pressure. Alternatively, I'd think one could make a simple electric air pulse pump(hooked to the crankcase tap input on the walbro) that would use much less power than an electric pump and let the Walbro diaphragm pump function as intended.