what i have noticed with the 125cc thumpers ect is they do have plenty of low end torque so by reducing the rear sprocket size down a few teeth should still give this engine the needed power torque for starts, i do know 1st gear on these bikes is ratioed quite low, so you could try either a larger front or a smaller rear. i have a 125cc provert coming in for some mods shortly and i will let you know the gearing on this.