I have built dozens. The 1st thing I do is add an air pod and adapter, change to a better flowing exhaust and go with bigger jets. I make my exhausts and drill my own jets but you can find all of it in a kit. I also file the timing key to advance the timing a bit. They retard them from the factory to pass emissions. Under the tank there is a rod from the governor linkage to your throttle linkage. On that rod is a spring. Put a small zip tie on it to keep it from expanding. This will give you more RPM'S and allow you to still use the stock throttle setup. Dont worry about a new flywheel. The stock springs will float the valves before you get to the point of danger. I have been ditching the stock carb and have been using a pz22 slide carb on my newer builds. People are always saying how bad the carb on their 212 is. It is not a bad carb, it is just not made for motorsports. It is designed to run equipment at a constant RPM. If you take your stock carb off there is a plastic spacer behind it. The side facing the carb has a round opening, the block side has a larger D shaped opening. You are allowing way more flow when you change carbs and ditch that. You will have to remove your governor but again, the stock springs won't let you rev to the point where you will damage anything. Your throttle response will be so much better. Before you even do any of these I would slap a torque converter on. That will give you the best bang for your buck. My favorite kart has a stock 212cc with a torque converter. My favorite bike has a hopped up 196cc and a torque converter.