Abstract This paper deals with the relationship between grain yield and grain losses during harvest. Measurements were carried out on a combine harvester with axial harvesting device allowing various adjustments to combine harvester parameter settings, such as rotor speed, gap between separator and rotor, fan speed, holes of the upper and lower sieves. Values of harvest losses in combine harvester with custom settings for the given crops were compared with values of losses obtained by a harvester with manufacturer’s recommended settings. This paper observes the losses in grains of spring barley and winter wheat crops. All the measurements made showed lower grain losses when the combine harvester settings were customized. In general, custom settings provided quantitative losses lower by 0.198% than settings recommended by manufacturer.