A harvesting combine rotor cage top cover assembly comprising: (a) an overhead roof formed from a substantially horizontal flat section and downwardly angled side sections; and (b) a series of substantially parallel vanes (62, 78, 80, 82, 84, 86, 88, 90, 92, 94) located beneath the overhead roof, each vane being formed from a substantially flat top section located against the overhead roof horizontal flat section and from downwardly laterally extending legs at opposite ends of each vane, the downwardly laterally extending legs being angled on their sides and having an arcuate bottom, the ends of the vanes being rotatable about a central pivot, whereby the flow of material in the rotor cage can be promoted or retarded by rotating the vanes, additionally comprising: at least one bar assembly (96, 98) located atop the overhead roof and which attaches about at least one end of the vanes (62, 78, 80, 82, 84, 86, 88, 90, 92, 94) by means of bushing spacers (112, 122), at least one linear actuator attached to the at least one bar assembly (96, 98), arcuate slots (126, 128) formed in the overhead roof, and bolt assemblies (64, 66) extending through each vane (62, 78, 80, 82, 84, 86, 88, 90, 92, 94), wherein each arcuate slot, the at least one bar assembly and the harvesting combine rotor cage top cover assembly are configured such that moving the at least one linear actuator (70, 72) results in gang rotation of the vanes (62, 78, 80, 82, 84, 86, 88, 90, 92, 94) about the bolt assemblies (64, 66), characterized in that the vanes (62, 78, 80, 82, 84, 86, 88, 90, 92, 94) and each bar assembly (96, 98; 100, 102) are divided into sections and the sections comprise at least an upstream section and a downstream section extending along the overhead roof and the spacing between the vanes in the downstream section is narrower than the spacing between the vanes in the upstream section. (a) an overhead roof formed from a substantially horizontal flat section and downwardly angled side sections; and (b) a series of substantially parallel vanes (62, 78, 80, 82, 84, 86, 88, 90, 92, 94) located beneath the overhead roof, each vane being formed from a substantially flat top section located against the overhead roof horizontal flat section and from downwardly laterally extending legs at opposite ends of each vane, the downwardly laterally extending legs being angled on their sides and having an arcuate bottom, the ends of the vanes being rotatable about a central pivot, whereby the flow of material in the rotor cage can be promoted or retarded by rotating the vanes, additionally comprising: at least one bar assembly (96, 98) located atop the overhead roof and which attaches about at least one end of the vanes (62, 78, 80, 82, 84, 86, 88, 90, 92, 94) by means of bushing spacers (112, 122), at least one linear actuator attached to the at least one bar assembly (96, 98), arcuate slots (126, 128) formed in the overhead roof, and bolt assemblies (64, 66) extending through each vane (62, 78, 80, 82, 84, 86, 88, 90, 92, 94), wherein each arcuate slot, the at least one bar assembly and the harvesting combine rotor cage top cover assembly are configured such that moving the at least one linear actuator (70, 72) results in gang rotation of the vanes (62, 78, 80, 82, 84, 86, 88, 90, 92, 94) about the bolt assemblies (64, 66), characterized in that the vanes (62, 78, 80, 82, 84, 86, 88, 90, 92, 94) and each bar assembly (96, 98; 100, 102) are divided into sections and the sections comprise at least an upstream section and a downstream section extending along the overhead roof and the spacing between the vanes in the downstream section is narrower than the spacing between the vanes in the upstream section. at least one bar assembly (96, 98) located atop the overhead roof and which attaches about at least one end of the vanes (62, 78, 80, 82, 84, 86, 88, 90, 92, 94) by means of bushing spacers (112, 122), at least one linear actuator attached to the at least one bar assembly (96, 98), arcuate slots (126, 128) formed in the overhead roof, and bolt assemblies (64, 66) extending through each vane (62, 78, 80, 82, 84, 86, 88, 90, 92, 94), wherein each arcuate slot, the at least one bar assembly and the harvesting combine rotor cage top cover assembly are configured such that moving the at least one linear actuator (70, 72) results in gang rotation of the vanes (62, 78, 80, 82, 84, 86, 88, 90, 92, 94) about the bolt assemblies (64, 66), characterized in that the vanes (62, 78, 80, 82, 84, 86, 88, 90, 92, 94) and each bar assembly (96, 98; 100, 102) are divided into sections and the sections comprise at least an upstream section and a downstream section extending along the overhead roof and the spacing between the vanes in the downstream section is narrower than the spacing between the vanes in the upstream section.