Assuming it fits well, install a 1 inch piece of fuel line and find a suitable solid piece of metal or plastic (round of course and a snug fit) and plug the loose end. You will then fuel by disconnecting the line to the carb and pumping fuel into that line. Have the muffler line disconnected as you fuel or watch VERY closely so that you do not pump fuel into the muffler when the tank fills up. This would be necessary even with the 3-line method. On future planes, with cowled in engines, you may need a 3-line system but not for most trainers or sport planes. If you do disconnect the muffler line, pay close attention to which line goes where. If backward, it will not run properly long at all. Many color code the lines.