Wow, drum brakes with internal shoes. Maybe that IS a thing on go karts.... It is found on many a vintage and modern mini bike for certain.
Not sure what it is. It's pretty old, it is not a Manco, but it has nice, sort of upgraded precision spindles for the front wheels and the wide wheels and tires you can tell, are aftermarket/custom/not original.
Is that bell crank contraption in photo #4 for the brake or throttle?
That seat and engine sort of cover up key details on the frame, details that I'd prefer seeing but I'm at a loss as to ID.