Interesting rig, but have no idea what it is. Tell you what I see though, that would go a bit towards ID of it.............
3-piece bolt-together roll cage/rear rack setup.
Apparent replacement of motor platform with little to no adjustability of the motor for chain tensioning.
Built as a 2-seater, bench seat with sliders for seat adjustment. Wasn't enough, kid needed a block of wood popriveted(?) to brake pedal.
Can't really be too ancient, there's a safety warning label on the front that warns about not riding it after consuming drugs, and long hair getting caught in moving parts.
Left rear rim badly dinged, can likely pound it back with a hammer, but bead seat might be iffy.
You got your $150's worth in wheels, hubs, tires, and steering setup. The metal component is something you need to bend to your will, make it do what you need. Start with a welder, and make those weak bolt-together points into one solid piece, in a bad rollover your life might depend on it.
Next, put in some real seatbelts (harnesses), attached to real steel. I got my pair of color-matching (blue) 4-point harnesses from Walmart for $39 for the pair. Do like your safety sticker says and get DOT-approved motorcycle helmets.
Check out kart parts suppliers like BMI Karts, GoPowerSports, MFG Supply, etc. for things like a motor mounting plate w/slots, seats, non-slip pedals, sprockets and chains, throttle cables, brake parts, any goodies you can think of. You're already off to a good start.