I'm running a 46 tooth rear sprocket on my WR 450. It will come pretty damn close to 100. It's wound out like hell, but she get's up there pretty quick. I needed a little taller gearing for road riding. The WR still has enough down low power. The only negative to the 46 is in first gear riding technical terrain. You have to be pretty quick to feather the clutch when your trying to crawl through stuff. I'm hoping to score a Rekluse soon so I won't have to worry about it. P.S. I don't care much about top speed anyway, I prefer torque and acceleration over speed. These bikes don't have much business running 90+ mph anyway. They get a little nervous and are pretty well rung out. Get a rocket if speed is your thang.