Some have complained about 02 sensor issues. I have yet to experience it on mine I have 4100 miles on it since my purchase in august and it rides nice love the bike love the power delivery on the low end. No complaints from me if I had to do it over again with a few more years under my belt I would have gone for the s4rs. I love the s4r but I think that the better suspension on s4rs is well worth it. Good luck duc hunting.
-ghost
-ghost