How do I tune my Troy bilt? It idles fine in choke mode, but is hard to start. when i try to put it in high idle(normal) position it wants to die. I've cleaned out the bottom of the carb and changed the spark plug. I also tinkered with the 3 screws that adjust timing, air and whatever else. I can't seem to get it going correctly. Any starting adjustments on those screws I could try? thanks for the help.