What are you YZ-ers running for a rear sprocket? This Renthal aluminium one didn't even get me thru one year, that's about 100hrs for me. Since I ride primarily woods I'm thinking I can afford the extra few pounds for steel. Also would you change out the rear without doing the whole drive-train? My chain and countershaft are good for another few months but the rear is toast and I don't want to spend the bucks for what I don't need yet.