Another newby karting question

[GeoffNorthWales]

I come from a motorcycle road racing background so know my way around tracks and had a few seasons of autograss racing, but after many years in retirement and at the tender age of 48 have decided to give kart racing a go.

I am a stocky rugby player build 6 footer so will need some horse power to pull my lardy ass around any track , my question is after looking at many sites on the internet I am still a little confused. I fancy a 125 gearbox kart and after many years of racing TZ Grand Prix bikes understand how much set up these peeky motors will need, but my confusion is, is a 125 gearbox kart a superkart or could run in the open class ?, also there is a suitable 125 gearbox kart on a well known auction site but what is putting me off that is that it has a 6 speed Motori 125 engine but I cannot seem to find much info on this engine after a quick google search, all advice greatly received.