howling

Hey guys looking for advice on an 2006 fz6 with 13500 kms. Just purchased bike 2 weeks ago and i notice a slight howling noise that starts at 70 km/h and gets loudest at 78-80 km/h and starts to quiet up at about 85 km/h but do i still hear it at 100km/h as well. Doesn't matter what gear i am in...