Abstract: A harvester having a mobile base unit adapted for movement over the ground, a transversely extending crop harvesting header supported from the base unit for allowing pivotal movement about a generally fore-and-aft axis of the machine, and a lateral flotation system for pivoting the header about the generally fore-and-aft axis is disclosed wherein the lateral flotation system includes a two way hydraulic actuator means extending between the header and the base unit for pivoting the header in the one or the other direction and positioning the header in a nominal position intermediate opposed extreme positions prior to starting flotation operation, a pressure source coupled by a pair of pressure fluid supply lines to the hydraulic actuator means, and energy storage means connected to the hydraulic actuator means.