Basically you can run this engine up to 20 minutes with a cup of warm water (the engine must be cool). The bigger the temperature difference between the top and bottom plates the higher RPM you will get. This works best with a hot cup of water underneath and an ice cube in a plastic bag on the top (there is plenty of room for one ice cube on top).
Have it on a coffee warmer with coins stacked on it to raise the engine to slow the engine down. Works continually and is fun to watch.
Out of the box it wasn't working. I had to balance the piston and flywheel so that it moved a little more freely. I moved the wheel so that the piston was at it's highest position, lifted off the cylinder to let air in, then closed the cylinder. After that I put it on top of my CFL table lamp and it was warm enough to get it going.