I picked up a brand new 2008 YZ450F a couple of weeks back and have only ridden it up the street a few times thus far. I typically like to get my bike set-up with my after-market goodies before taking it out for the first real ride. I prefer to run an X-Ring chain and a Stainless steel or TiMoly rear sprocket. The combination of the two tends to last several seasons for me. I bought an RK520XSO X-ring chain that I found for a good price on eBay, but I've not decided on what size rear sprocket I will want to run for a combination of off-road and track. Will the stock rear sprocket last fairly long in combination with my X-ring chain? Or, is the stock rear sprocket going to be trashed fairly quick? I don't want to put this X-ring chain on if the rear sprocket is junk and thus junking my new chain in short order too. Should I just run both the stock chain and rear sprocket until they're trash? If the stock rear will last me an entire season, I may just run the X-ring chain on it.