Lesson 2/Learning Event 1
IMAGE: FIGURE 44. EXHAUST STROKE.
Thanks to the flywheel, the crankshaft starts the piston moving up on the exhaust stroke. The upward
movement of the piston pushes the burned gases out through the open exhaust valve. Just before the piston
reaches the top of the stroke, the intake valve opens and clean air rushes in. This forces any burned gases left
out through the exhaust valve. This is called scavenging the cylinder. The exhaust valve closes and the piston
is then pulled back down by the crankshaft and flywheel, and the intake stroke starts the cycle once again.