It has been routinely noticed that the stock speedometer is not precise. The error can be up to 10%, which can be tested by any speed measuring device put by police on the roads for your convenience, or by a modern GPS. This error is not limited to Kawasaki, or even motorcycle, speedometers. Automobile manufacturers routinely install speedos that read fast, most likely to avoid being sued if their customers get speeding tickets.
There are several ways to remedy the situation: