I replaced the chain and sprockets on my 06 ninja 650r. I went with a chain and sprockets ordered off ebay (2006 2015 Kawasaki EX650 Ninja 650R O Ring Chain and Sprocket Kit Orange | eBay) cost around $70-$80. In my opinion it looks and performs great. I noticed a big recovery in power delivery after installing (mostly because my old chain was crap). I also recommend doing it yourself since my shop quoted me around $100 for labor. Not too hard as long as you have the right tools.