peugeot speedfight 100 w reg?

how do i check the cdi unit, it has 2 4 pin plugs all black wires, i have a diagram just not sure what i should be getting out them as i have no spark or feed to coil , earths are ok and some feedsbut unsure as what signal i'm ment to get from the sensor on the what looks like a flywheel . any help as to what is ment to come out all the wires would be a great help , and if it is fried the best price for a replacement?
cheers