I have not seen a superkart faster than 143. A strong 250 single on a laydown will go 145. Lots of “stories” about Hines going 160+, but the real deal is he went in the low 140’s, according to Marc Crozlyn. Russell jr went 156 in the BRC 250 twin on a laydown and most knowlegeable folk said then that was about the fastest anyone has went.
Two sharp superkarts drafting can get 144.