from what I understand if your carb is Mikuni you can buy a new main jet (#110), take apart your carb and unscrew main jet and replace with new jet, if you're upgrading your air intake and amount of fuel entering the carb you may need to adjust your carb settings slightly to get it to run smoother. You can also change the sprockets making them larger or smaller on both the front and/or the back to either increase acceleration, or reduce acceleration and lengthen out your gearing to increase top speed. These are all changes I will be making soon on my XVS125 soon, to give me a bit more of a helping hand on the 70mph dual carriageways.