Rejetting is simple. Multiple companies offer rejet kits such as nr racing, OldMiniBikes, affordablegokarts, etc. When you recieve your new kit you will turn off the fuel valve and remove and drain the golden bowl on the bottom of the carburetor. After that, you will see a narrow hole with a brass fitting in the center. That is your main jet. Simply unscrew this jet and give the carb a tap to remove the jet and emulsion tube. Reverse the process with the new parts and you are good to go. How much do you weigh and what type of Riding are you doing? 16 is very tall and would have an extremely slow takeoff.