Removing the rotor on the engine (slider) to replace it or to access the centrifugal governor mechanism.
Having unfastened the latches, remove the cover of the sensor-distributor with high-voltage wires.
Using a slotted screwdriver, unscrew the two screws securing the rotor to the base plate of the centrifugal regulator..
... and remove the rotor.
Install the rotor in reverse order. Wherein…
... the square lip of the rotor must fit into the groove of the base plate, and the cylindrical lip into the hole (for clarity, the distribution sensor is removed).