The first thing to check is the speedo sensor on the front wheel,it is a magnetic pulse sensor and has a magnetic composite rotor iside the speedo sensor that sends pules up the wire to the speedo head these rotors break very often especially if it has had a tyre change or the front wheel has been out and back in and not out in the right position.other then that you need to check the wiring from the sensor to the clocks or loom and see if its ok then its a case of replacing the speedometer assembly.
adam bike doctor(of milton keynes motorcycle centre), January 2011
