The piston is a plunger that moves back and forth or up and down within an engine cylinder barrel.It transmits the force of the burning and expending gases in the cylinder through the connecting rod to the engine crankshaft.As the piston moves down in the cylinder,during the intake stroke,it draws in the fuel-air mixture.As its move upward,it compresses the charge.Ignition takes place and the expending gases cause the piston to move toward the crankshaft.On the next stroke,it forces the burned gases out of the combustion chamber.
