First is to look for obvious leaks. If gas or vapor spray is comeing out the vents on the pump while it is running its a sure sign of a bad pump, or gas getting into the oil. You can check it with a pressure gauge, it should put out 3-5 lbs pressure. You can take the line loose at the carb & put a glass or can under it. Start the engine. It should fill the container in a few seconds. Those transparent filters always act like that. I dont know why. From your syptoms it sounds to me like its an ign problem. Take out a spark plug or 2. See if there is a black carbon buildup on them. That can cause an intermitant miss.
