Disclosed is a harvesting combine rotor cage top cover assembly that includes an overhead roof formed from a substantially horizontal flat section and downwardly angled side sections. A series of substantially parallel vanes are located beneath the overhead roof. Each vane is formed from a substantially flat top section located against the roof horizontal flat section and downwardly laterally extending legs being angled on their sides and having an arcuate bottom. The sides of the vanes are rotatable about a central pivot for promoting or retarding the flow of material in the rotor cage.
