Abstract: The invention is concerned with a combine harvester having a threshing mechanism for separating harvested crop into grain and crop residue and a guide mechanism for directing the flow of crop residue from the threshing mechanism along one of three paths, the guide mechanism comprising two deflection doors that can each take up one of two positions. Each of the doors of the guide mechanism is supported on a pivot shaft fitted with a crank arm and a resilient element connects the two crank arms to one another in such a manner that each door, independently of the position of the other door, is urged by the resilient element to remain in one of two stable end positions and passes through an unstable over-centre position when moved from one stable end position to the other.