An agricultural harvesting machine for crop material including a crank arm connected to a rotational power source, a plunger having an extended position which is located further rearward in a compression chamber than a retracted position, and a connecting link connected between the plunger and the crank arm. One of the connecting link and the crank arm has a variable length. The plunger moves between the retracted and extended positions during a run mode as the crank arm rotates. The plunger changes speeds during an event phase based upon one of the connecting link and the crank arm varying lengths.
