Motors are not Engines.

Steam Engines:

http://science.howstuffworks.com/transport/engines-equipment/steam.htm

http://www.animatedengines.com/locomotive.html

Stirling Engines:

http://auto.howstuffworks.com/stirling-engine.htm

http://www.animatedengines.com/vstirling.html

http://www.animatedengines.com/stirling.html

http://www.animatedengines.com/ross.html

2-stroke Engines:

http://science.howstuffworks.com/transport/engines-equipment/two-stroke1.htm

http://science.howstuffworks.com/transport/engines-equipment/two-stroke2.htm

4-cycle Engines:

http://auto.howstuffworks.com/engine1.htm

(single cylinder)

Intake, Compression, Combustion, Exhaust

http://auto.howstuffworks.com/engine2.htm

(more typical, and more complex)

http://auto.howstuffworks.com/engine4.htm

What goes wrong typically?

http://auto.howstuffworks.com/engine3.htm

http://science.howstuffworks.com/transport/engines-equipment/two-stroke1.