Dalton, asking for “anything about karting” is a bit like asking for “anything about football.” The question is so broad that a 10,000 word answer still wouldn’t be complete. You might try going to amazon.com and looking for books on karting, like “Karting, everything you need to know” by memo gidley.
To answer your specific question, yes, a 6’1 245 pound person can fit in a kart, though you wouldn’t want to be any bigger than that. And you can have plenty of fun. I know people your size who race karts. However, you will almost undoubtedly will not win races or even be particularly competitive, as the ideal kart racer is about 5’6″ 145 lbs, much like a Formula One racer. In fact, F1 racers use karts to train and practice in the off season. I tell all the big guys, “remember those little guys in high school that we used to push around on the football field? Well, this sport is their revenge.”