You sould check the manufacturers plate, Its kinda like a VIN plate on a car. You'll find it at the very front of the frame, right behind the front forks, the plate is commonly black with silver words. You will find your serial/VIN #, Your MODEL #(very important when asking possible model specific questions.
You'll also find the month & year your Motobecane was made as well as your Carburator Info and MPH Rating.
also if yours was made before Jan. 1978 the volyage on the magneto is 6Volts, If after it is 12 Volts.
Check the Manufacturers plate out first, Everyone wants to think there model is a Mobylette, But they all aren't.
Hope this helps focus your questions better,