piston rings?

hi there, ive been told that the piston rings need to be replaced when the kick starter is very easy to kick. also would it not start the engine on the kicks because it needs a new piston ring? it starts on kick, but you have to give it a lil gas. Also, does anyone know where i can buy them? i dont know wich ones to buy or where i could order them. i have a 1990 yamaha yz 125. any information is greatly appreciated! thanks!
-Tony

ok, but i dont know exactly what i need, i know i need the piston rings, but is that all you have to replace?