Lesson 1/Learning Event 1
FIGURE 11. INTAKE STROKE.
Intake Stroke
As the crankshaft is rotated by cranking, the piston is moved to TDC to start the intake stroke. At the same
time the timing gears turn the camshaft, the cam lobe under the intake valve is beginning to open the intake
valve.
As the rotating crankshaft pulls the piston down, it draws or sucks the fuel-air mixture past the open intake
valve into the combustion chamber.
When the piston reaches BDC, the intake stroke ends. The cam lobe has moved from under the tappet,
allowing it to rest on the base circle of the cam. The valve spring now closes the intake valve and seals the
fuel-air mixture in the combustion chamber.
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