Alan--I haven't completely ruled out Jan Ridders engines. Jan does some great work, but I know of a number of people who have built his two strokes and couldn't get them to run properly without modifying them. He does take a very novel approach, having a separate "expansion chamber" instead of using the crankcase as part of the induction system. Obviously they do run, I've watched the video's of them, but I was hoping for something more conventional, more like one of the aero diesels used in model aircraft, only with a lower compression ratio and a sparkplug rather than a glow plug.---Brian