ok if you look at the pump you will see 3 pipes on it 1 is from the fuel tank ther next one the same size (thickness) goes to the fuel inlet into the carb and the other one is the vaccum pipe that goes to the carb inlet manifold,this pump is called a pneumatic fuel pump and is operated by fluctuating pulses of air from the inlet whcih pushes a diaphragm back and forth which in turn pumps the fuel.so if you want to prime the pump the only way is to take the vaccum pipe off the inlet manifold and suck and blow on it for a about 30 seconds this will be plenty enough to get the fuel into the carb again,i have not ever heard of a vaccum pump being damaged by running it out of fuel.
adam bike doctor(of milton keynes motorcycle centre)
February 2011