Is the PGM ok?
Assuming the valves are free, try removing the servo from frame then remove the pulley and seperate the top and bottom of the servo, be careful as theres quite a few plastic gears in there.
Eventually the motor and the potentiometer will be revield, a simple test on the motor and the pot can be made.
Burnt out motor, snapped wire faulty pot etc.
Never had chance to give the exhausts a good airing yet then!!
Never did get my bike sorted, sold it now
All the best,
Regard's Phil