A method comprising rotating a rotor to expel, radially, a mixture of grain and material other than grain (MOG) from the rotor and past a rotor cage encircling the rotor causing an air flow in a substantially arcuate channel defined by the rotor cage, a first cover assembly covering a substantial portion of the rotor cage, and a passive sieve, to entrain a first portion of the MOG capturing a first portion of the grain with the first cover assembly and plural vanes located along the length and on the interior surface of the first cover assembly, the captured grain sliding by gravity along the vanes to the passive sieve, the captured grain comprising threshed and unthreshed portions enabling the passage of the captured grain through the passive sieve and into a second channel within which a grain conveying assembly is disposed conveying with the grain conveying assembly the passed, unthreshed portion rearwardly and conveying with the grain conveying assembly the passed, threshed portion forwardly.