Derbi gp1 speedo problems

Hi All, I have a derbi gp1 250 2009, the speedo is in kph which isn't a massive problem, the problem is that the speedo is showing a very high reading, most of the time I am travelling at 199 kph!! Before I start stripping parts, what. An cause this ? Thanks for any help

 

i would try changing the speed sensor first, if that doesnt fix the problem then its the dash itself...

 

Thanks for the reply, any idea if I can test the sensor?

 

nope. no idea and ive never tested one, just replaced them as they are the cheapest part to replace.