Ok, I've rested the continuity of all the wires going from the control unit at the rear to the servo,
Tested continuity if the wire from the Cdi to the control unit
Tested there is power at the control unit
Tested the servo motor
Tested the ohms of servo pot meter (5ohm) is correct
Cleaned all the connections
Have two control units maybe there both gone?
Is there any way to test the control unit?
Servo make slight movements when ignition on but will not move once the revs increase

Any ideas would be appreciated