I cleaned my stove this morning. It's a Harmon Accentra. It had stopped burning this morning. I then pulled the back panel off & discovered the chain had come of the motor gear/sprocket. I've put it back on but it keeps coming off. Does the chain go over or under the tension wheel? I cleaned the fines out from under the burn pot. Is there another place to clean to get the XXX@@###%@@ chain to stay on!! Thanks for any help.