Abstract: A speedometer gear output structure includes a gearbox installed in a motorcycle and holding a driven gear and an output gear for synchronous rotation with the wheels of the motorcycle, an annular magnetic device fastened to the gear shaft of the output gear for synchronous rotation, and a circuit board mounted in the gearbox and holding a sensor corresponding to peripheral magnetic zones of the annular magnetic device for outputting an output signal indicative of the speed of rotation of the output gear.