2-stroke engine conversion for steam

Is seems natural to me to accompany wood-based heating system with small (<1kW) electric generator. The following conversion looks pretty good, but the construction is still unknown. Can anyone share the detailed construction of such type of conversion? The benefits are: simplicity and reliability due to no valves.

That looks like an air compressor that has been converted into an air motor, not a spark engine converted to use steam pressure.  The supply hose in that video is common plastic air line, and would not abide steam pressure at over 212 degrees for very long at all.  What you really would want is an actual steam engine kit.  Google can find them.

I agree that the machine shown is an air compressor (or motor) rather than an internal combustion engine.

Although a steam engine is efficient and simple, to safely build and operate one requires a significant understanding of its principles.  I don't consider it to be a DIY project for the untrained.  Live steam at high pressures can be extremely dangerous.

It's not quite the same shebang, but the someone from Tamera designed a nice sterling engine, a solar powered sterling engine. I think you would like to learn more about it.´