It is not just a nut that you are missing. There is also a short (4 inches) piece of tubing that has some holes in it, that goes inside that larger aluminum piece at the back end. Without it your nut (with washer) will plug the pipe. Also, when that piece blew out the back, that did not cause your ped to quit. It will run without it. Something else caused it to not run, and perhaps caused it to backfire and blow the pipe apart.