A rotor feeder unit for an agricultural machine, such as an agricultural baler. The rotor feeder unit includes a rotor feeder, and a drive for driving the rotor feeder. The drive of the rotor feeder unit include an input that is configured to be coupled to a power source, an output coupled to the rotor feeder for rotating the rotor feeder about its axis of rotation, and a variable ratio transmission coupling the input and the output. The variable ratio transmission includes a variable-diameter input pulley, a variable-diameter output pulley, and a belt arranged between the input pulley and the output pulley.
