Kantor　proposed　a　spark　ignition　engine　model　to　predict　engine　cyclic　variation　in　terms　of　some　assumptions.　In　this　paper　a　modified　Kantor　model　is　proposed.　We　show　that　exhaust　blowdown　process　and　variable　exhaust　residual　gas　mass　fraction,　neglected　in　the　Kantor　model,　significantly　reduce　cyclic　variability.　However,　prior-cycle　unburned　fuel　not　considered　in　the　Kantor　model　apparently　aggravates　cyclic　variability　of　next　cycle.　These　three　factors　interact　on　each　other　and　result　in　abatement　and　even　disappearance　of　cyclic　variation.　No　significant　cyclic　variability　is　predicted　for　realistic　ranges　of　these　parameters.　Only　for　extremely　unrealistic　ranges　of　model　parameters　cyclic　variation　reluctantly　shows　up.　Moreover,　even　using　the　Kantor　model,　cyclic　variability　is　predicted　only　for　rather　extreme,　somewhat　contrived　choices　of　the　model　parameters.