Hello,
first some explanations
Normal control of the engine RPM is made by a flexible control (teleflex) which move a lever on the M53 regulator.
If this control is blocked or cut there is an electrical motor on the engine which can move this lever (the "secours carb).
To test the secours carb
At iddle position of throttle you toggle the secours carb baber pole cover (you can observe the increasing of engine RPM)
then you try to accelerate the engine with the small joystick to see if electrical motor is working properly
finally you close the cover (engine RPM decrease to normal value).
As I remember you never test secours calc on normal procedure