Do you know how much hp the karts have? I imagine there 5.5 hp or 6.5 hp honda's? Well, the main point is, dont hit the brakes too hard if the engines are this small. Just come into the corner, as far outside as you can get, tap the brakes twice, and only twice. Then turn in as late as possible, but make sure you still hit the apex. Make sure you turn smoothly. If you turn too hard, that will kill the engine RPM's just like brake would.
Good luck,
Kenneth