Anytime I have access to the speedo cable (when I have either of my fairings off), I always disconnect the cable from the back of the speedo, and drop 3-in- one oil into the cable, until I see it bleeding from the other end, at the wheel drive adapter. I also lubricate the throttle cables whenever I have the throttle tube assembly off.
I know some may disagree with this practice, saying it only attracts dust to the cables, but I've never had a cable break, or unravel. The stock inner cables are not stainless, and will eventually corrode and break. Keep the suckers lubricated! Any moving part need lubrication!
Cheers!