Check the distance between the abs ring on the rotor to the sensor. When I bought mine, same thing - the previous owner changed the front tire and dropped the wheel beveling the reluctor ring (is that what it's called?). My mechanic removed it and flattened it in his press and after putting it back, all was good in the world. The light went out and the ABS worked again.
2010 Honda VFR 1200F
2003 Aprilia Tuono