everything that everyone is saying is good, but I have to ask what are you using the kart for? running around the neighborhood and having a little street fun is one thing...a stock predator with no modifications would be fine for this...if your taking it on the track, then several mods would have to be done to give you longevity and improvements.
one...low oil pressure and governor removal...for messin around home...leave it alone. if your racing, get rid of them, google "predator governor removal" for a vid on how.
two...rod...depending on your use, a billet rod would be the best for racing....but if your racing, the rules may prohibit it's use.
three....cam....stock cam is fine with stock lifters, pushrods, springs, etc.., for playin around....but if you upgrade for serious racing, then you need to look at new springs, chrome moly pushrods, higher lift/longer duration cam....and everything has to be kept inline to get the best possible power.
four....carb....what you want is to set the carb to go along with the improvements that you do...with more improvements, your engine is going to want to breath more...so you have to look at the etube, the jets, the air filter...all of it so that you don't fuel starve the motor.
five...oil...ready everything on bob's on the different oils and what others say and then make your won mind up.
six....don't forget to get a big box of fun...
you may be thinking "I know this already" and I don't want to sound condescending or that you don't know. just want to help!!