A system for cleaning a flow of harvested crop including a suction device between an inlet (1) and an outlet (3), the inlet being equipped with a hood (5) in which is formed a circulation path of the flow of suction air between the inlet and a suction opening (6). The suction device further including a drum (7) rotating relative to the hood, the hood being positioned in the drum to form a suction area (10) on the exterior of the wall, the suction area being delimited circumferentially by respective upstream (10a) and downstream (10b) edges. The system further including a conveyor (11) for the flow of crop, a device (12, 13) to recover the portion of the flow of crop that is not sucked up, and a device (14, 15) to recover the portion of the flow of crop that has been sucked up in the area. The circulation path of the hood (5) forms a deflector for the flow of suction air, the deflector is arranged to balance the speed of the flow of air along the suction opening (6).