I spent almost 4 weeks chasing down electrical gremlins as the possible cause for the speedometer suddenly not working on my 2002 R1200C. Sent out the speedometer for testing; swapped out the speedo sensor cable on another bike, and everything tested fine. Removed and opened up the miles of spaghetti that makes up the speedometer harness looking for broken grounds, shorts, etc. Pulled fuses and relays from the electrical junction box. Called everyone I knew, and some folks I didn't know looking for advice. After all that time and aggravation, it turned out that an $11.00 part, known as an Impulse Sending Wheel, had actually somehow come loose from the crown gear shaft inside the final drive. It was held onto the shaft loosely by the tapered bearing, so it didn't go anywhere, but it caused no impulses to be created with the wheel rotation, and therefore, no speedometer working. I brought the parts to my local welder and had the impulse wheel welded to the crown gear shaft, never to come off again (I hope!) Lesson learned...always look for the easiest, most obvious mechanical issues that could be a cause-and-effect item, before delving into the never ending, process of elimination electrical nightmares that newer bikes offer. Of course after losing endless hours of sleep for the past month, I did a search for "Impulse Sending Wheel" on this site today, and found the exact same problem, only mentioned once, back in 2007. Had I looked here first, I would have been riding for the past month, instead of dissecting my bike. 2nd lesson learned.