An adjustable vane system for use with a rotor cage of a threshing system of an agricultural harvester includes a vane. The vane includes: a generally helically curved inner profile; a surface being an outer profile that is opposite the inner profile and is generally helically curved over a portion of the vane, the outer profile being configured to be positioned closer to the rotor cage than the inner profile; and a flat portion located midway along the outer profile.