As I'd mentioned above I had got my hands on a 'pre-milled' kit to build a Bengs Modellbau 'Nick'.
A small Flame Licker engine.
The engine comes pre milled with the kit of parts vacuum packed to two cardboard sheets. I found this kit to be of excellent quality and great value for money. The drawings had a few omissions that needed a bit of thought to work around. The assembly instructions suffer somewhat from translation issues, but again for the price paid it is still superb. I had some issued once the engine was assembled in getting it to run consistently. I spent a day or two pondering this alongside making minor alterations to the cylinder head. Making this slightly thinner than specified. The remainder of my time spent was to ensure the cylinder was perfectly sealed, this mean lapping in the joints between the cylinder and head and inlet valve and head. When spun backwards, the vacuum now drawn pulled the engine in the correct direction where it would complete around 5 revolutions.
The piston is bronze running in brass and requires little lubrication. the main bearings are ball races.
Having been so impressed with this engine, I've decided to purchase a set to build the larger flame licker engine and a thermoacoustic engine.
I'm awaiting to see how much this will cost me in import charges!
The video below shows a short spell of the engine before lighting as well as a spin round of it running gently.
I have found that to run this engine requires a minute or two of warming up, after this period it will run consistently for around 15 minutes.