1 - In order to beat a Stock bike in initial pick up you need more torques, will need bigger stroke (longer Cylender block+crank_conrod)
2 - In order to beat a Stock bike in top speed you need more cc wider piston more high revs, will need bigger piston wider block.. More Horse Power.
once you have more torque and horse power then you need to improve reduction ratio to tranfer al horse and torques to wheels then offcourse bigger clutch would help
finally final drive also reduced to give good top end.
when this high level of alterations will be done bikes life will be short.