i have 15/38 in my super power 2012, all stock, the torque is good even with pillion, but vibration start just after 60km/h, however it went easily to 60km, and if you give it a more of trottle it goes upto 80 km and that is the max..
i am thinking to change the front sprocket to 16 i.e. 16/38 and if the vibration is still there, i will change the CDI to altas CDI, along with Kara...