I have a 2002 cat atv 500cc. The connecting rod is shot! How hard is it to change

 

Real hard...disassembly of major engine components (split the case) and replacement of the crankshaft which comes with the rod. Rod knock can be due to a number of things...compression, carbon build-up on piston, firing poorly. Could be piston noise which is much easier, or internal case components like starter idler gears. cv pullies and/or cv belt if you're so equipped.

Greg