To achieve good performance only head cylinder never make it speedy, one has to change many other things...
1 . valve : 125 Altered valves (prefer steel valves)
2. Head : Bearing wala head with buffed piston cone
3. iridium 125 Plug
5. Cylender : 124cc
6. Crank/Weight : 124cc
7. Magnet : 124cc
8 Pulsar : cbr250 or fzr both can work
9. Ignition coil : booster bottle
10. Piston : 124cc quad bike piston
11. Clutch : Qinqi
12. FinalReductionRation : Qinqi
13. Final sprocket Ratio : 15:35
14. Carburator of atleast 200CC Honda RoadMaster
15. tyre : 3.00/17 : 2.75/17
16. Dont forget to add a CD-175 Drum brake in front as it would need better braking.
and an Expert mechanic to really do it well, a poorly altered bike will be bull S**T