08 yz450f sprocket wear

Got this new to me bike and noticed on the small sprocket there is obvious shiny wear to the outside of it what does this mean thank you for your time

And what's the pro and con of an x ring vs an I ring chain

The bright almost polished wear on the sides of the front sprocket is normal.  Gauge the wear condition of the sprocket by the tooth profile, not by the looks of the sides.  The teeth should look symmetrical, with no "hooked" appearance.


"X-ring", I-ring, "Z-ring", etc. are all just different variations on sealed chains that use seals with small lips or sealing edges on them, as opposed to simple O-rings.  The letter used to ID them is a reference to what the cross section of the seal looks like, more or less.  There is very little advantage of any one of these over the other, or for that matter, over O-rings.  The idea of such seals is to reduce the friction caused by O-rings, but that's not a significant thing, anyway.


Sealed chains will last longer than non-sealed if you don't abuse them by power washing them.  You primary interest should be in finding a chain that holds up over time, not in the trickest form of seal they use.


The Regina ORN6 is an extraordinarily good one, and a good value. 


Good graphic, but that should be "Good" and "Really Really Worn" :smirk:


It's worth mentioning that front sprocket wear as illustrated in the photo above is caused by a chain that was run longer than it should have been.  (This predicated by viewing the pictured sprocket as if we were looking at the out-facing side of it, "forward" being to the left)  Wear that hooks the front sprocket toward the rear ( and the reverse of that at the rear sprocket) is caused by the chain being too long to fit the sprockets correctly.  As the chain rolls onto the front sprocket under power (or off of the rear), each roller is supposed to settle squarely into the center of the round valley between the teeth, never touching the point of the tooth, but rather, making contact with the back side of the half circle valley.  As the chain wears at each of its pins, the pitch, or distance between the rollers increases (this is incorrectly referred to as "stretching") until the roller first comes into contact with the tooth point, wear it begins to apply drive force pressures and wears one side of the tooth off, leaving the rearward "hook". 


Read how to determine when to replace the chain: http://www.thumpertalk.com/wiki/_/when-do-you-change-your-chain-r368


Now, having gone through all of that, The pictured sprocket actually looks like the back side of a Honda sprocket, so for the sake of the discussion, let's flip it over and look at that (see pic, forward still toward the left).  If you replace your chain according to the link above, you might find that you can reuse at least your rear sprocket, and maybe the front, but eventually, sprockets run on dirt bikes, even with chains "stretched" less than 2%, will show wear like the attached pic.  The difference is that the chain that caused this wear was still the right size, but the mud, sand, small animal fragments, etc., that have been fed across the thing over time have worn the driving side of the tooth valley back into the meat of the cog.  Note that the area on the rear-facing side of the tooth (inside the red boundaries) look nearly like the new tooth, while the area below the front sides of the teeth are hollowed out.





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