An agricultural vehicle includes a chassis and a header carried by the chassis. The header includes: a header frame; a cutter movably coupled to the header frame; a reel arm pivotably coupled to the header frame; a reel carried by the reel arm and including a plurality of tines; a variable displacement fluid cylinder including an interior chamber, a first piston linked to the reel arm placed within the interior chamber and a second piston placed within the interior chamber, the interior chamber defining a shared volume between the first piston and the second piston; and a piston driver linked to the cutter and configured to translate movement of the cutter relative to the header frame into displacement of the second piston within the interior chamber.