Custom Gokarts

This video is a follow up to bikes, just as a self propelled vehicle transforms the human into a moving vessel that he attached himself too, a go kart is the next level up and its pipes and systems become so much more complicated with motors and smoke and gasoline. Personal vehicles too small for freeways can be insanely dangerous when they are built custom and supped up to go at dangerous speeds, just how far can you go in this genre of vehicle? What do people build and how do they avoid bodily harm?