One can fit nitrous to their bikes in order to gain more speed and torque. Though it is not common. NOS cylinders contain Nitride-oxide that makes your engine smoother i.e. it nourishes your engine with regards speed and power. The more Nitrous you use the more powerful your bike becomes.
Basically NOS cylinders contain a handful of gasses like ammonia nitrate, nitrous oxide, nitrogen and various other variations of nitrogen. These various gasses fuse inside the combustion chamber at a temperature of 240 degrees.
The gas produced at such high temperatures produce smoke, steam and results in more speed and power. So for obvious reasons when you see bikes with nitrous leading the race do not be surprised. In bikes with nitrous what basically happens is that the system delivers more oxygen in the engine at regular intervals.
The oxygen delivered at regular intervals combines with the nitrogen gas and other gasses and burns the fuel at a faster pace; this produces more power and efficient torque.
Whenever the oxygen is taken in to the engine, it combines itself with the nitrogen stored in liquefied form and this will drop the temperatures to lower levels at the intake charge. In simple terms this means that the engine becomes more capable of burning more fuel and air simultaneously. The temperature downfall at the intake manifold will result in increases power and fuel available to engine.
The power of your engine increases 100 to 300% from the current level. So unless you have good high end bikes nitrous cannot be used. It can even destroy your engine if it proves to be incompatible.
This kind of NOS operations are supported only when the bikes are mechanically transformed to fit the nitrous requirement. Thus, it can be stated that NOS can eventually turn your bike to a speed jet but one needs to be careful while installing them. Be careful that your bike is properly modified to compile with such high level mechanics.