Mine speedo reads 10% faster than the GPS also!
I just figured out how to use my Garmin to record trip distance.
On my bike the odometer, on one 42 mile trip, recorded 3.7% more miles than the GPS.
Love the bike but feeling serious contempt for the KTM customer service arm!
One month after starting to make calls to the KTM USA Customer Service phone number ((440) 985-3553) I still have to get a reply.
I especially like this on KTM US's web site,
"Phone calls made to the Customer Service line may be monitored and recorded for quality assurance purposes " Quality Assurance my ass! I've never had one of my calls to them answered! Not one! The voice mail thing throws you into unanswered loops punctuated by annoying beeping, offers to go back to the main menu which puts you back into the same loop and then, finally, dumps you into the answering machine.
http://www.ktm.com/us/contact.html