Many people wonder if sprocket and
rear tire changes will affect their speedometer reading ?
How do you know you have an electronic speedometer ? Check the back of your dashboard and look for electrical wires (not for the light of course....) going into it instead of a Bowden cable. Also check a service- or parts-manual for the location of the speed sensor.
How do I know where my mechanical speedometer is connected to ? Follow the Bowden cable from your dashboard down to either the Front wheel or the Gearbox.
Now if you found out that the answer to the question above is 'YES' and you do want to correct your Electronic speedometer, you can use a device called a SpeedoHealer. Just do a search for it on the Internet. A SpeedoHealer can correct your electronic speedo so it is exactly in line with for instance a GPS attached to your bike. Since all speedo's come with a default deviation of about 5-10%, the SpeedoHealer can also be used on a bike with stock sprockets.
As for the mechanical speedometer connected to the gearbox, they cannot be corrected. The only thing you can do is use the Gearing Commander to calculate the differences caused by changing sprockets and or tires and keep the result (in percent) in mind while driving....