Abstract: An adjustment mechanism to affect a change in the size of openings through a sieve in a combine harvester is disclosed wherein the handle for actuating the sleeve adjustment is positioned above the surface of the sieve to permit an ease and convenience of access. The handle is pivotally connected to a pivot member and movable between a retracted position in which the handle presents a streamlined profile to minimize obstruction to the flow of crop material thereover and an actuating position in which an engagement pin in said handle is engageable with a notch formed in the upper surface of the pivot member to permit the handle to actuate movement of the pivot member, which in turn is transferred into a fore-and-aft motion of a slat connection member interconnecting the sieve slats to be adjusted to affect a pivotal movement thereof.