Abstract: An axial flow combine harvester is described which comprises a rotor having a thresher section and a separator section. The thresher section includes pairs of rasp bars, which are staggered from one another along a helical path. Individual rasp bars of the pairs of rasp bars are located adjacent to the separator section of the rotor. The individual rasp bars are removable to render the action of the thresher section less aggressive. To reduce the risk of plugging when a trailing rasp bar is removed, a flow deflector plate is mountable in place of the removable rasp bars so as to guide the crop flow continuously from the remaining rasp bar to the infeed end of the separator section of the rotor.