So i just bought on 05 zx10 well when riding it back i had my girlfriend drive next to me and when she was doing 75 my speedo was showing 90 mph. Now the previous owner said id has stock teeth but i woud like to check myself. what is the stock teeeth on the front and rear sprocket. If it does have stock teeth is this normal to be this far off or do i have a problem?

 

17 front 39 rear

 

Thanks