Is Gixxer 250 SF BS6 have vibration issue at higher rpm?

Out on the highway, the motor feels unstressed at speeds of upto 100kmph, with an optimal cruising speed between 90 and 100kmph. This shows in the highway fuel efficiency, which is the highest of any 250cc bike we have tested. You can ride it at 120kmph as well but the motor starts to feel stressed at those speeds. This is a refined, vibe-free mill with just a hint of buzziness creeping in on the fuel tank and handlebars post 5500rpm.