I,ve got a problem ! Power delivery on my YZF750 seems very "flat". When I turn on the ignition, Idon,t hear theservo motor working. I,ve removed the EXUP valve cover and when I turn the pulley clockwise, then turn on the ignition, the servo closes the pulley. Am I right in assuming the cables just need adjusting/lubricating ? When I turn on the ignition, should the valve open & close? Any help appreciated!

this is how i verify the operation of my exup valve, with the cover off of the valve (as you have done), warm the engine up and let it idle. The pulley wheel has 2 lobes these should be either side of a hole/recess (the hole is for calibration, presumably in the factory with a setting pin), rev it up (over 6000 rpm) and the pulley should be rotated by the cables (attached at the other end to the servo)

if it doesnt, its mostly likely one of the following faults:

Poorly adjusted cable

Seized exup valve

Servo not getting electricity/conenction fault.

Servo stripped gearing or failed motor.

ignitor fault.

Broken cable.

All checkble, to check the servo take the cables off and do the test the servo should rotate at 6000rpm ish. Also if the servo is not 'home' when the ignition is turned on it should reset.

To check seized valve disconnect the cables and twist the pulley by hand, it shouldnt have resistance. If it does, realistically you are gonna need to take the downpipes off the bike and get the valve cover-plate off, expect to have a bit of agro with it and you will be okay. Use high temp lube, when reassembling, molybdenum grease being popular.

Good luck

Thanks for advice! I,ve disconnected cables and the valve turns quite freely. Will try starting and warming bike tomorrow to see if servo works. Unfortunately, bike is indoors at the moment, don,t think neighbours would appreciate the sound of Micron race pipe reverberating through the walls! Anyway, cheers for help!

Hi, just to update, I stripped, cleaned & lubed the EXUP valve. (It was squeaking when I turned it by hand.) Reassembled everything, adjusted the cables, took the bike outside & fired it up. I let it warm up, revved it a few times & the valve is working fine. Thanks again for advise!