i bought a 2000 zx7r and i am trying to figure out all that was done to the bike as far as aftermarket parts. i know very little about bikes so i am hoping for some help. My bike has a vortex rear sproket, i am not sure about the front one. It also has a gold chain that says GXW 520. how do i find out what size sproket i am running? and when you change out said part, do you usually do the front one too? And what does the +,- mean when referring to sprokets? i know they are newbie questions but how do i learn without asking.