Sorry to bring back one of my long dead threads but I wanted to add to what I said. The stock qt rear gears are 10/57 and the pw gears are 11/54. This gives you a 12.5% top speed increase at the same engine rpm. With the pw gears 30mph equates to the engine turning at 6,853rpm instead of 7,791rpm with the qt gears. I GPSed my bike today to check the acuracy of my 1422mm wheel circumferance measurement and I'm dead on, I'm actually really suprised that it wasn't off by atleast 1mph at 40+mph but it wasn't off at all. I GPSed my bike at 43mph in a half tuck on flat ground with no wind. I'm wanting more power to kick in at 40mph to push hard to 50mph and so I want to build a pipe for that rpm. 40mph with the pw gears equates to the engine running at 9,141rpm. What I want to know is is it smart to sustain my engine at that rpm? Before doing the math I didn't know I was sustaining 9.5Krpm! I want to hit 50mph but at that speed the engine will be rotating at 11,374rpm!(sounds like disaster to sustain it there but then again I don't know). Is it just smarter to lengthen my drive shaft and run a larger diameter rim and tire????? Thanks. Ryan.