My Trane XR80, horizontal, upflow, propane hot air furnacehas a yellow, feathery flame on the lowest burner. This also causes a back draft (roll out?) on that burner with the door in place. With the door off it burns just fine, I had it burning for half an hour this afternoon. How do I clean the orifice, just with a cloth or Q-tip in place, or should I remove the burner assembly? Does this yellow, feathery flame indicate a perforated heat exchanger? Thanks in advance for any help,
Tony