My new RK O-ring chain didn't last a year and has chewed up two sprockets in the mean-time. Man these 4 strokes eat up chains. My 92 KX 250 had a RK o-ringf chain that lasted 7 years but couldn't get a year out of the 426. I confess that I don't touch the chain other then to adjust it. Rarely oil it and never wire brush it. So I will never get as much life out of a chain as some of you. But then again, same maintenance was used on the KX with great results. Must be the torque that is eating these chains. So what chains and sprockets last the longest?