Old muffler rusted out. Bought a FO-4 from Tractor Supply, bolted it up and now it wont fire. I'll get a pop every once in a while.\n\nCan take the muffler off and it will fire up. Put it back on and nothing.\n\nAnyone have this problem or install the FO-4 muffler? Hoping I do not have to rejet, hoping it can be adjusting with screws....Where do I even buy new jets?