Piston rings

Piston ring primary function is to seal the combustion chamber and keep the pressure that builds up on the compression stroke from escaping. Another function is the rings provide a means for heat to transfer from the piston to the cylinder wall and then to the cooling system to keep the bike from over heating. The last function piston rings serve as is in a four-stroke engine, the rings act as a seal between the combustion chamber and the engine oil. This oil control ring is used to perform this function and is located and is located furthest from the piston crown. 

The gap between each piston ring is very important. Because that would make a difference in the performance of your bike while riding. 

This is what the Piston rings look like: