What is the best Go Kart Engine I can get?

It has to be under $200, and I want to know if it is good.

Go to harbor freights and you can buy a blue engine that is 6.5hp for $150 i think. It is not name brand but it is good. They made a whole go kart class just for that engine since it is so good and cheap. If you want to know more about it google box stock engine.Make sure it is a horizontal shaft for a go kart