Systems, apparatus, and methods for tensioning systems of a drive belt are disclosed. Particularly, tensioning systems for a drive belt of a rotary screen of a harvester combine are disclosed. The tensioning system provides for avoiding over-tensioning the drive belt when the drive belt is disengaged from a drive shaft. The tensioning system may also provide for maintaining continuous operation of the drive shaft as the drive belt is moved between engagement and disengagement with the drive shaft.