alteration in sprocket can give you a little edge but remember its "a little" ...i would like to know more about the "racing grari" by the way joking :D,
to get 20+ kmh speed gain you will need a complete engine swap..
or rahi baat engine swap ki tu meray bhai bas itna samjhe lijye... ik aag ka darya hai or doob k jana hai...
let me share some of my imaginations... (these all engine are swapable to china 70 with little to no alteration in frame)



