An agricultural harvesting machine (100) for crop material is disclosed. The agricultural harvesting machine (100) for crop material comprising: a crank arm (142) connected to a rotational power source; a plunger (146) having an extended position which is located further rearward in a compression chamber (140) than a retracted position; and a connecting link (144) connected between the plunger (146) and the crank arm (142), one of the connecting link (144) and the crank arm (142) having a variable length, the plunger (146) moving between the retracted and extended positions during a run mode as the crank arm (142) rotates, and the plunger (146) changing speeds during an event phase based upon one of the connecting link (144) and the crank arm (142) varying lengths.
