I can not say how to set it back to factory settings, but if you go to the Horizon web site i am sure that they will be glad to tell you. I can say that i have a Hangar9 PTS Mustang and the Instructor that trained me was delighted at how the engine ran and preformed. His main plane is a 102 inch YAK with a twin gas. And his comments have always been how great it runs time after time. It put out this grayish stuff for a while and now runs great.