Top Speed of a Bike

crankshaft and the gearings of bike matters , but at the same time the efficiency may decrease

The top speed depends on various factors.
To start with, the engine volume/capacity. Or as it is said 'cc'.
Higher it is, Higher the power, and higher the speed.

Then comes into play the 'LOAD' on it. It includes the weight of the bike, weight of the driver and pillion, and many other factors. As the load increases, the speed decreases.

Then the 'Loses'. Frictional Loses in the engine, Gear box, Chain/propeller shaft, etc.
Higher it is, Lower the speed.

Then comes the shape of the body. The more aerodynamic it is, the higher speed it can touch. Because, if its not aerodynamic, the air in the surrounding will offer friction, and reduce the speed.

Then the tyres. Now, this is something that everyone doesn't know. Traction (between road and tyre) is an important feature for the safety. Higher traction ensure higher safety. But lesser the amount of traction, the higher speed can be obtained. Now, in indian vehicles the traction control thing is rarely found. Because in low speeds, the change is very infinitesimal. But at higher speeds, say, 200kmph, you will be able to note the difference. The traction control system can be found in German cars.

Higher the bhp , higher will be the top speed.