A separation device for separating a cyclone chamber from a collection chamber of a cyclonic separator has a guide member that includes a leading end, a trailing end, and a guide surface. The guide surface guides debris entrained in an airflow in the cyclone chamber in a helical path about an axis of the separation device and into the collection chamber. The guide surface extends about the axis of the separation device through an angle of less than 360 degrees for allowing debris in the cyclone chamber to also pass into the collection chamber from the cyclone chamber in an axial direction. The leading end of the guide member is at an angle between 30° and 60° towards the cyclone chamber with respect to the axis of the separation device to promote a helical flow of air and debris flowing over the guide surface.