I love go-karts, I wonder when they were invented .
not sure, but I definitely tore around in them as a little boy with a small motorless model. in fact, I still ride them, but much more high powered versions!
Do you think they have variations of go-karts, like with different engines. 
definitely. you can have a four-stroke engine or even electric motors. sometimes I'll feel a little lazy and just ride around in a two-stroke
IT there an organization responsible for regulation for the different class of engines ?
no it's pretty much anarchy out there in the go kart world. in fact, some wild child put their minds to making a SIX stroke engine. that baby really tears it up!
OH, that would be interesting... but could someone start racing go-karts and be promoted to real car racing ?
oh yes. go karting can be a stepping stone into more intense and skillful motor sports like formula 1. I would never dare though!