John: yess the nipple on the Muffler is clear. I used a plastic pump to test it and it is clear of any obstruction. I could feel air coming out the 2 exhaust pipes, so it must be clear.? I will run a pin through it tomorrow, but I don't think that is the problem. True, the muffler is not creating any back pressure, or at least not enough to pressurize the tank, that's why it dies, I think. I am thinking of using a Perry pump to see if that makes it work and bypassing the muffler altogether.