Hi, Is it possible that when you installed the new jet that you either got the float stuck in closed position , or that you put a hole in the vacuum diaphragm in the carb? Either of these thing would allow gas to reach the carb but NOT flow into the engine. Another thing to check is the operation of the auto choke valve. It is the black solenoid attached to the carb on one side. There is a wire leading to it. Is it still attached? This would make cold starting difficult if it is not functioning.