Join Date: Jun 2008
Location: New York, NY, USA
There are probably several causes for idle surging on the K12. On mine, a 2008 K1200GT it was the airbox that was causing a high idle when engine was hot. The throttle would hang up in a high idle, making for some interesting situations when trying to stop the bike at a light. A newer, updated airbox corrected that problem.
You will have to determine that all other maintenance items have been addressed before anyone can assist you with troubleshooting your idle surge.
To start with, what year and model, mileage, service history and status are you dealing with?
2008 K1200GT, Custom Paint, Vivid Black, Aeroflow WS & Aeroguards, Givi E52 Maxia Topcase w/AdMore Lighting, Zumo 660, Suburban Footpeg Lowering, Sargent Seat
2009 R1200GS Adventure, Magnesium Grey/Black, Adventure Cases, Zumo 660, Touratech Unobtanium Accessories
1974 Norton Commando 850 Soon to be a restoration project