I had my S-T 40 pop and start one day, cold, when attaching the glow driver. I had just gotten a real rechargable one, that made the plugs glow white hot (more than my "d" cell one did). I primed, closed throttle, got starter on plug and engine just went "pop" like a backfire and was running. Made me very glad I was so paranoid around engines - and this was BEFORE I stuck my finger in the damn thing!

Andy