You really shouldn't have to pump it at all. Auto chokes require one pump to release the cam and set the choke, and sometimes if the fuel level is low in the bowl the engine will have to crank a bit to fill it up, but the choked carb should provide all the gas you need without pumping.
I have the "B" on my 261 set up with an auto choke and I can start it right up in any weather, even after sitting, with a very short amount of cranking, and it doesn't stall once it starts.
My procedure is to pump the gas once, take my foot off the gas, turn the key on, step on the starter, and it fires right off. Even with points ignition.
