Can Anyone shed any light on this issue, I've always had this problem on and off and have never got to the bottom of it I haven't really used the bike over the last couple of years and has disconnected the servo but now I've just given the bike a good going over and want to sort this problem out.
Servo works when you turn ignition on but stops as soon as I ride it then if I stop bike turn ignition off and on it works again until I go up the road.in the past i have changed the servo control unit it's gradually got worse over the years.

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

Hi m4rk79,

do you fixed the problem? I have same problem on the power valve servo.

Hello m4rk79
Your controlunit is receiving a pulse from the front cdi unit,maybe that pulse
from your ignition is not ok. Maybe your CDI unit has a failure .But it,s only a guess.
Let me hear when you found it.

Gr Jasper