Speedo show about 15 Km/h to much.
Show 100 km/h but real speed is about 85 km/h.
can U calibrate/adjust some speed sensor or some thing to get the speedo to show almost right speed when riding?

// regards Goran
XtZ660 -09

That's a well known problem, the solution is either a GPS to show correct speed or a speedohealer
http://www.healtech-electronics.com/products/sh/

Ciao
Solitario

If the difference is that big, i'd check your gearing first.
Stock gearing is 15t front and 45t rear.
With your difference, front sprocket would be smaller than 15 or rear would be larger than 45.