...:bang: D'Animal once again has provided invaluable insight. I had presumed that if it had a "bulb" it was for priming (my Honda trimmer calls the bulb a "priming bulb") and assumed that meant "pumping" gas into the carb venturi ... when it apparently means it is pulling gas through the filter...
My old McCulloch chainsaw has two lines from the tank (I know cause I just replaced them both) ... one feeds directly to the carb .. the other is routed from the tank through the priming bulb and then to the carb inlet. I have therefore concluded that the priming bulb is only used for "priming"...