Did you check the filter screen in the carb itself? If you never flushed out the tank with fresh gas to get out the paraffin and excess plastic well when the fuel is pulled in up to the carb it has to go thru the filter screen inside the carb, one side of the carb is the pump and the other side is the filter screen and the diaphragm so be very careful and take your time in taking this part of the carb apart because if you just take screw out and pull apart you can really damage the tiny fingers that sets the diaphragm to the way the engine runs, the diaphragm is more or less what is the needle that meters the fuel thru the carb, but try to check the filter screen inside the carb before you do anything else.