30th Jan 2015, 13:36
You don't have to pump fuel, just pull the choke. If the thermostat had been faulty, it would be in the open position, and water from radiator flows to engine and makes it cold. Thus reducing the temperature. It needs at least 90 degrees combustion temperature. In your case, after a while it runs normally. This shows it attained enough burning temperature. When you pull the choke, the carburetor is shutting off air, thus preventing cold air.
28th Jan 2015, 12:06
Pull the choke and let the engine warm a bit. I think it is only hard to start when the engine is cold, like in the morning.