Maybe you don't have a go kart. Why not build one? Here are some other instructables on how to build yourself your first kart:
Make your own Go-Kart.
Design and Make Your Own Go-Kart
It doesn't matter how many wheels it has, it doesn't have to be a 3 wheel like mine, it could have 4 wheels or even 2 (mini bike), the same basic principles apply.
Stay tuned because the engine section applies to any small engine, like what is found on lawn mowers, pressure washers, generators, etc.