How good is the stock rear sprocket?

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.

The sprocket doesn't junk the chain, the chain junks the sprocket. If you replace the POS chain the bike is delivered with with something that will hold up for a while, the OEM rear will last about a year or more. depending mainly on how long the chain stays in spec. The one on my older '06 lasted a year and a half until the Regina ORN6 chain I put on it needed replacement.

I left the stock chain and sprocket on my bike to see how long it would actually last. Well, 5 rides later the chain was so stretched out that it started to bend the tips of the teeth on the sprocket over. That stock chain is a piece of crap!

The stock sprokets are really good.

I've got a tick over 1K offroad miles on mine and there is practically no wear. I expect them to go another 2K miles before they need replacement. I guess I'm lucky with my WR in that the stock chain is actually decent...which is probably helping sproket life in my case.

In the OP's case. Junk the stock chain but keep the stock sprockets (if that gearing works for your application). You should easily get a year out of the sprockets if you're MXing. D.I.D just came out with 520 VT X-ring chain thats supposed to have the strength of a heavy duty chain but is narrower.

Stock sprockets are fine. Toss the stock chain ASAP.

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