Re: Racing Go-Kart Project
I have a buddy whose son races go-carts. I think they are using CR250F engines. They go very very fast but I don't know how quick the acceleration is. Maybe you need to go with a CR450F engine just to make sure you kill youself even faster! 
From talking with my buddy it seems like a lot of the guys around here really like the honda engines over the other manufacturers but they are all so similar that any would work.
The other option is to put a Kawasaki Bruteforce 750 engine on it with Nitrous. That will definitely do what you want. I have a stock Bruteforce 750 and for a big quad it is quite quick!
Here are a couple videos I found that show the Bruteforces with Nitrous. They are quite quick. Keep in mind that the Brutefroce quads are a little over 600 lbs so the same engine on a 100# go-cart chassis would be unreal.
http://www.youtube.com/watch?v=qlzqYYFjdf8
http://www.youtube.com/watch?v=sGGXb4A_sq4
