The speedometer on my 77F is not reading correctly. It tells me i am going faster than i actually am according to my GPS. Its off by about 8-10 mph @ 60 mph, so it tells me i'm going around 68-70. The speedo works off the front wheel, so the only thing i can think of that would affect it would be if the front tire size were smaller than stock. According to the book a 3.25-19 is stock size, and i have a 100/90-19 dunlop, which is supposed to be the same size. any ideas as to the problem?
thanks