This may sound stupid but; the front end is connected to the back end. Things you do to the front, effect the back, things you do to the back, effect the front. The quickest way to stop a push is to narrow the front, or widen the back, but don't widen or narrow both. Another way is to put more weight percentage on the front. A push in left-hand corners, or right-hand corners, suggests, in some cases, a bent frame. Get the kart on a set of scales and find out what the corner weights are. Bathroom scales will work just fine as long as there on a flat surface. Also front to rear. Get the front corners to weigh the same, the back wheel weights as close to the same as you can get them, and start with a 45% front 55% rear. Work from there. What kind of bracing do you have on the seat? How wide is the front and rear tread width. Center to center of the tires.