Honestly speaking, these 100-200cc 4 stroke engines are not designed/capable of speeds above 110km/hr in normal conditions. These are not rockets to take you on moon. In 80s there were 2-stroke machines like RX115,GTO125 etc called pocket rockets bcoz they were able to go 130km/hr but again speed thrills but kills. So If you want speed >120 km/hr either switch to 350cc+ 4-stroke or 125cc 2-stroke machine.
Our friend Haris once said in his tarekhi khutba : "There is no replacement for the displacement*."
In 92, I had a five star Honda CG-125. It were my teenage days. Once I raced with a Kawasaki GTO110 and found that my bike was unable to go beyond 95km/hr while GTO crossed me easily. Later I saled out CG and purchased a GTO125 which used to go upto speeds of 125km/hr. I also kept a Honda CD-200 twin which went smoothly upto 105km/hr. My Suzuki GS-150 went to 100km/hr on a straight road when I was coming back from Balochistan to Punjab and I can say that max it can go is 105km/hr (in normal conditions). Hypothetical Figures quoted by different people are often false or not normal. Once one of my relative said about these kind of people :"Either they are incompetent or biased". Or they do it, for the sake of fun, to make others fool. So in todays world, its always important that who is quoting/saying.
On a seperate note, a 800cc car's normal attainable speed is 120-130 km/hr so what do you expect from a 125/150cc engine bike. In my personal opinion, one should not try to take a 125/150cc bike above 90km/hr irrespective of that whether its capable of exceeding that speed or not for the sake of one's own safety. And I tell you the actual(realistic) top speed of these bikes: Suzuki GD110: 90km/hr, Honda CG125:95km/hr, Suzuki GS-150: 100km/hr. Max you can stretch is upto 105km/hr unless you are not riding on an inclined surface.
*:Displacement refers to the horsepower(cc) of the engine.