In general, a 100cc 2-stroke motor for a bicycle will be faster than an 80cc 2-stroke motor. The displacement of an engine refers to the total volume of all the cylinders in the engine. Since the 100cc engine has a larger displacement than the 80cc engine, it typically has more power and can produce higher speeds.
These variables can influence the overall performance and top speed of the bicycle.
It's important to adhere to local laws and regulations regarding the use of motorized bicycles, as they may have restrictions on engine size, speed limits, and other requirements for road use.