This particular engine we’re looking at has four strokes: the intake, the compression, the combustion (or power), and the exhaust. Smarter Every Dayvisited the guys of 805 Road King and their see through engine to show us exactly what’s going on in an engine when we fire it up and it’s pretty fascinating stuff.
It’s much easier to understand what’s happening in an engine by, well, looking at a see through engine because you can see how the strokes are all connected but the basic actions go like this: the intake stroke is when the air-fuel mixture gets drawn into the cylinder. The compression happens when the intake valve closes and the piston in the cylinder pumps up to compress the gas. The combustion happens when a spark plug fires up and ignites the air-fuel mixture, pushing the piston back down in the cylinder. In the exhaust stroke, the gas pumps out the exhaust valve.
It’s obviously slightly more complicated than that (but not by much!), so you can watch the video by Smarter Every Day in the video below. He does a fantastic job illustrating everything.