I just did this mod and I'm pleased with the results. The bike starts much, much easier than with a rejetted stock carb, the top end is improved, throttle response is better, and the darn choke lever is in the right place now. Trevor was right about that. I have some jetting specs, for those interested. I live near sea level, and the temperature was about 45 to 50 degrees when I jetted. Here's what I have so far: 40 pilot, 2 turns out on the fuel screw 125 main leanest clip position on needle (for now) I run a BBR pipe, and have the airbox mod along with the BBR free flow filter. The bike starts with little or no choke, and runs without the choke immediately. The bottom end response is crisp, and it revs right through the mid to the top end with improved response. The torque feels stronger too, as taking off in third gear is now no strain compared to before. I'll post updates after a race or two in warmer weather. There was a fitment issue with the airbox boot. The 200X carb's intake bell is actually a SMALLER diameter than the stock one, yet the body of the carb is longer. What I did was use a Dremel tool to trim 1/4" off the boot where it meets the carb. This way the boot doesn't need to bend and deform to fit the carb. Also, the boot is a smaller diameter there, allowing a better fit at the carb intake. It appears close to stock now, and runs even better.