Its been a long time since I last rode either a CD70 or CG125. In my college days I had 125. And I remember that one of my friends has a CD 70 and he had done some alteration on it to make it go fast. One thing that I can remember now that he changed the front gear or Garari of the chain. I thing it had more cones than the original one.
Having said I will again emphasise that dont think of doing these speeds on these bikes. These speeds are dangerous for even the most sophisticated bikes. In our road conditions and on these bikes let it be CD 70 or 125 its extremely dangerous.
My advice keep the bike you have and drive careful and slow. I remember someone uploaded a video of a Lahori biker who died while doing stunts and speeding on his bike. I can understand that you are young and want to have some thrill in life; but one can be intelligent at any age.