It takes a minute or so to fill the carbs, and the pump may cut out too early (presumably a safety feature)... if so, switch the ignition off and on again to reset it. Once the pump stops properly try the starter. If the pump keeps going every time you switch off and on check to see if one of the carbs is flooding.
Also check you turned the fuel tap back on. :lol
Also check you turned the fuel tap back on. :lol