1 month old xp 700 needs modding

i have an xp 700 electric pocketbike and it needs to be moodded. it goes about twenty miles an hour and rides perfectly. but i need more speed. i have had this pb for about a month now. does anyone know how to mod this without damaging the batteries or frying the electronics over time?
i made a +5 kit by myself but im not sure if that will damage my controller. also i have a 13 tooth sprocket that i might put on. please help.