My first race vehicle was a Microd, like a full-bodied kart only with a wood frame. We used Tecumseh H35 engines, 3.5 hp with left rear driven only. That was in 1988. Switch to a 6hp 4 years later, and my final year was in what amounted to a quarter-midget with a 5hp Briggs similar to WKA specs.
Good training ground for being smooth and total momentum game.
My first kart was practicing with a friends’ 28mm Swiss Hutless with a 100cc Formula A spec Parilla TT36 Revenge. Direct-drive with an IBEA slide carby and breadbox sides only. Violent acceleration in every direction. Everything since has been a letdown except my foray into club ICA with BeaverRun using a 100cc water-cooled Haase Titan engine. Of course running at 330# instead of the more bulky 375# required for TaG may have something to do with the lack of feel for TaG, and the clutch changes things too…
For a newb, any 4 cycle seems like a good choice. Except for maybe a Biland. :)