So I'm kinda kicking myself in the head for ordering a complete chain & sprocket set from ebay that supposedly fits my 2005 SV650. I take off the old sprocket and immediately notice something is not right. As you can see, the one that was on the bike as this raised inner portion as well as the holes. The new one is completely flat, with no holes. With the old one in, the sprocket sits flush against the point where the threading for the nut ends. With the new one, there is some space that should be filled by that raised portion. I'm pretty confident that they send me a sprocket that straight up doesn't fit my bike, unless someone can tell me what I'm missing here. 

Also I'm pretty sure the last owner never torqued the front sprocket nut correctly or never put locktite. I went and borrowed my dad's breaker bar, assuming that there'd be a small brawl between me and the nut. Nope, the thing came off so buttery smooth that I wasn't even sure that the socket was sitting over the nut. 

Lastly, does anyone know the specific name of the washer in the 3rd photo? I'd like to buy a new one because I'm kinda paranoid about reusing it considering how loose the nut was. I've seen some used ones on ebay when googling stuff like "sv650 front sprocket lock washer." If you could help a brother out, it would be much appreciated. 

This can't be right, right?