Clive,
I am wondering if the engine type number, 223 on the report you have seen was incorrect as the diesel version seemed to have been shelved and tests continued on a petrol engine, the Jumo 222, your post with a scan in it gave the single cylinder engine a low compression rating so it was not the diesel test engine, see this excerpt from the link I posted;
Tests continued into 1942, but the engine’s reliability was a concern. The vibration issues seemed to be a result of the two-piece crankshafts and crankcase and the high rpm needed to produce the desired power. Along with the Jumo 223, Junkers was developing the Jumo 222—a 24-cylinder, spark ignition engine close to the same power and physical size as the Jumo 223, but lighter and of greater displacement. The Jumo 222 engine had more than its share of problems, and it made little sense to develop two engines in the same power class at the same time. In addition, developmental engines capable of more power than the Jumo 223 were needed.
Vibration and cracks on the 223 diesel engine seemed to be serious problems and I don't think the engine got any further than a test bed.