I checked my 1300R speedometer with my GPS. It was slow by six miles an hour. I was only doing sixty miles an hour when the speedometer was reading sixty six. No wonder old people were riding my butt. Programmed the speedohealer and the speed is dead on. The odometer is not clocking miles as fast as it was before. Now the odometer is reading a little closer to accurate. Cars and motorcycles alike can be as much as 15% off and still be legal. May get you a ticket but the vehicle maker can get away with it.