Hi, I have a 2003 LT80 that is all original except an FMF exhaust, UNI filter and Jet kit. There is a rattle somewhere in the engine towards the top end. this is "ONLY" at idle... when it revs the rattle stops and when it is warmer it isn't as prominent or doesn't rattle. Is it the rings??? I am dumbfounded because it runs like a champ! Help me...