I moved away from aluminum rear sprockets years ago. No matter what the manufacturer says (or the guy at the parts counter), the aluminum simply does not last as long as steel. I can have one steel rear sprocket (I use JT's, and they are strong and cheap) and one O-ring chain for an entire year. Non O-ring chains last a month if you ride much at all. In fact, the O-ring chain I used two years ago was still in the van as a spare, and we wanted to check some different ratios on my son's KX125. I popped off a few links, and to my surprise, the link I removed still contained grease! That chain had at lease 4000 miles on it, so should have been shot, but still worth using.
I have heard all of the arguments about rotating mass, the extra weight, and all the other hype, but hey, you ride a 500cc bike that puts out a lot of power. Can't say that the steel sprocket has ever put me in second...that's usually reserved from just being too old to run with the young guns anymore.
Rick
