re: diesel moped.
I like microdiesel engines, but I don't think the carbs on most mopeds are tuneable for it, and the heads might not take it (pop).
It would be interesting to see if anybody has an old HT, if they can cut a flat steel plate for a head and get a HT to run on Diesel. You'd have to run the idle screw all the way out so you could starve it of air with the throttle twister. You could use a small electric element to heat the plate or carb bowl, even some resistance wire and a small battery.