My Friend and I have had a similar prob with his TH .46 . We havent tried yet (we will this weekend), but we think that the muffler isn't pressurizing the fuel tank enough to get the fuel to the engine. We are going to try a different muffler and see what happens. You may want to try as well. The problem with his is we cant get the engine to run with a nose up attitude. Let me know if you figure it out because when we had it running, this thing screams!!