is not about mechanically wrong things sooty, they are set so show 10% less. this is happening on my 2012 xvs (this bike was come on the market first time in 2009), noth my wife cars (2004 and 2005) show 10% more than actual speed. if your car show you the correct speed, then your speedo is broken :)) first time I was thinking my bikes have the speedo broken, then I ask my mechanic and he tell me they are set like this, thing confirmed by a biker police officer and if I want check my speed, I should use the GPS because this is giving data in real time. the cops are against using the GPS to check the speed from safety reasons - sometime when is bad weather the GPS are stuck and is not showing you the actual speed and you risk to p;ass a camera with increased speed than the GPS showing you. but in normal condition, you can check the speed with the GPS so you can find out what is the difference between what speed you have and what speed your speedo are showing you. what cost you to check your real speed with your GPS? then we can speak again about your modern car-bike that show the real speed