250 superkarts are what I think you are talking about? Some are single cylinder (ICE) some are twins. Many drivers run the likes of CRF450’s also. Even if that’s not what you’re thinking, it’s about as fast as you’re going to get. Jonny west had a gixxer based superkart TAG project going a few years ago that was positively insane.
Anyway, you won’t see them on a typical sprint course, too tight for them to flex their power but they usually run in “unlimited” type classes in road racing on the big tracks like Mid Ohio, Infineon and so on.
See if there’s a road race near you, tweak the search distance if you need to: