how does an engine work?

[Seeker]

This guy with a high speed camera met up with some engineering wizzes who'd made a transparent cylinder head for a Briggs & Stratton engine. Initially running on propane, they switched it to petrol to give a more visible flame and filmed it.

https://www.youtube.com/watch?v=xflY5uS-nnw

They then decided that they wanted to see a carburetor in action so they made a transparent one and filmed it:

https://www.youtube.com/watch?v=toVfvRhWbj8

[Bibio]

the most interesting point in the first video was seeing the wasted spark.

[punyXpress]

Suck, Squeeze, Bang, Blow.

[gadget]

I remember watching a similar video using a BSA B50 single, it was all in the interest of learning exactly what the change of fuels, compression ratios, squish bands, valve shape, flame kernels, and the effects of timing and overlap.
Really interesting to see exactly what was going on with all four cycles at varying revs etc.