20 mph speedo error???

[pekingduck]

Been in discussion with the seller of a 2013 model and he says the only thing "wrong" with the bike is the speedo is off by 20 mph; it reads 80 when you're doing 60.

Now I've owned plenty of bikes with as much as a 10% variation. My current '08 GSX650f reads 70 when you're going about 63, but man.... 20mph???

He didn't mention whether the gearing had been changed from stock. If it's not that, it concerns me. Your thoughts?

CB1100s have an electronic speedo with a speed sensor on the rear wheel, so gearing doesn't affect the speed. Unless he's doing a burnout.