Weight is the two discs to which one end of connecting rod is connected to. On the other end piston is connected.
Through the rod piston and weight assembly to and fro motion is converted to radial motion.
Normally the bearings are worn out so there is side play in it so your weights are not Balanced.
Your bike might have vibrations and reduced performance due to it.
Google image for crank motorcycle to see it and ponder over its functionality.
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