I have finally all but eliminated it on my '05 R1200GS.
More than once I have asked for the throttle bodies to be balanced when in for service, and always got the response " they are within tolerance".
Last time I was told that the surging was because of one or more of these:
1) Free flowing BOS exhaust causing the exhaust gases to flow too fast for the Lambda sensor to measure.
2) Spark plugs getting old.
3) HID ballasts causing CanBus problems affecting the ECU.
Personally I felt that is a load of tosh, the surging existed long before any of the above were fitted! I will not be having any more sevicing done there BTW.
The resolution was to balance the throttle bodies myself, then reset th ethrottle position sensors. I have had a Carbtune mkII kicking around for years, armed with instructions from here and/or ADVRider I went about checking the vaccum levels on both bodies. They were definitely NOT in synch @ 3,500 RPM, adjustment was such a doddle I wondered why I had not done it earlier! For my bike i just needed to slacken the right hand cable by 1 1/4 turns of the adjuster and that was it.
The throttle psotion sensors were reset by disconnecting the battery. Then after 30 seconds ( not sure of this is requirement on a GS, but definitely needs to be done when resetting the NTL desk top box), reconnecting it. Turn ignition on, kill switch in the run position, do not start. Open throttle slowly to full throttle twice and back, turn ignition off. Repeat, this time opening the throttle 3 times because I cant find a thread that says how many times to do this.
Surging is now all but disappeared.
