Remove the power nozzle from the Kirby G4 by raising the headlight hood on the front of the motor to expose the belt lifter and the accessory lock.
Flip open the belt lifter handle and turn it counterclockwise until the red arrows on the handle and the nozzle line up. Turning the handle stretches the belt and lifts it away from the motor shaft.
Twist the accessory handle to the left to release the power nozzle from the front of the Kirby G4. Lift the power nozzle away from the vacuum motor. Turn the belt lifter handle clockwise until the green arrow on the nozzle lines up with the green arrow on the handle.
Place the power nozzle with the head light hood face down on paper towels or newspapers. Unlock the rug plate from the bottom of the power nozzle by turning the two latches toward the center of the nozzle.
Remove the rug plate from the bottom of the power nozzle. Grab the roller brush in your hand and lift it straight out of the bottom of the nozzle.
Slide the old belt from the Kirby G4 roller brush and discard it. Slide the replacement belt onto the roller brush, moving it to the center of the brush.
Install the roller brush back into the bottom of the power nozzle. Make sure the number of notches marked on one end of the roller brush equals the number of notches at the other end of the brush.
Cover the brush with the rug plate and secure it to the bottom of the Kirby G4 power nozzle. Twist the latches toward the outside edges of the nozzle to lock the plate in place.
Twist the belt lifter handle until the two red arrows line up, catching and stretching the new belt. Slide the power nozzle back onto the front of the Kirby G4 and twist the accessory latch to the right to hold the nozzle to the motor.
Turn the belt lifter handle clockwise until the two green arrows line up and the belt is released onto the Kirby G4 motor shaft.