I’ve owned my 2005 Honda CBR125 for around six months and it’s recently developed a problem where the speedo wavers annoyingly at around 60mph, occasionally sticking at this speed.
Joshterry93, MCN forums
You need to remove the speedo cable first (from the back of the clock and the front wheel) and then pull the inner out from the top. Check it first and fraying, if it's frayed it will need replacing. Clean the cable with a degreaser then grease it with some light grease.
Spray a little light oil down the inside of the cable outer and fit back together. Try spraying a little WD40 up the clock drive while the cable is off. Finally, check the speedo gear drive on the front wheel (strip, clean, grease or replace) and check it is meshing and driving properly.