My grandmother had an ID-6, roughly same engine but in an industrial/wheatland style machine. It was traded for a utility style machine when I was 2. I've heard tons of stories about it over the years, evidently it was one tough machine. Better ask an old timer, but I think you are supposed to switch back to gas before shut down, for easier starting---I know that was the rule on the older kerosene machines.
I bet George or Zippy would know.