I made this a while ago when I was experimenting with miniland scale vehicles and the greater amount of detail that can be worked into them. The steering mechanism is a simple rack and pinion system - it works well but isn't particularly robust. The miniland figure has to have it's legs removed then replaced in order to fit him into the kart, but stays put quite nicely once in place.
A close up of the steering mechanism.
Greebling on the back of the kart.
Without the driver.
At some point I'll break this up and try and put the steering mechanism into a larger vehicle - maybe some kind of 4x4?