Depends on the track you are on.
A go kart has a fixed rear axle, so when you try and go around a corner the rear tries to push the kart straight. So you introduce caster in the front so the kart 'falls' on to the outside front raising the inside rear.
A wide front track will raise the rear by less causing a bounce in faster corners when the flex overcomes the caster (you can hear this).
So why does the track matter? If you have a lot of hairpins or fast sweeps you want narrow front. If the track has lots of direction changes wider could help.
Good luck with your setup.