phalanx said:
I'm not saying that it can't be done, I'm just saying that I haven't seen a street legal 125cc motorcycle go that fast. Off hand I'm not even sure how fast 125cc MotoGP bikes go.
The human speed record was done on a stream-lined bike. Motorcycles in general have relatively poor aerodynamics compared to other vehicles on the road and they have a hard time pushing through the air at high speeds. The Aprilia RS125 which is known to be one of the fastest 125's out there is a 2-stroke that can hit about 120 when derestricted. A far cry from 150. A 4-stroke 125 wouldn't even be close.
Good point there too.......the ninja 250 has a top end speed of @120 mph.....
if you really want more power get a bigger bike, but if you want one of the fastest pocket rockets out there here is what you do....
Custom pipes
Look at your carb, what size is it, what type of throttle control do you have, jet size, ect......
look at your final.....can you put bigger on there, keep in mind you have a total amount of engine power meaning that if you gain top end you lose acceleration. you can gain back accel. by decreasing weight i.e. lighter wheels, lighter frame, running a on a no battery system, lose the burger and fries...
you can also reduce wind resistance, keep in mind its exponential with speed. install windshield and farrings (if you cant find any farrings for your bike, you can try using fiberglass, just will take lots of time and $$$).
i think you will get better bang for you buck by moving up to a 250-600 range, and just put some decent pipes and muffler with a rejet (gains from 1-15 hp)