It’s not too hard to do. Put the kart on the trolley, take the wheels off, hang two chassis hangers onto the rear axle just inside the hubs. Set the front steering to straight ahead and hang two more hangers on the front stubs. Now put two axles or equivalent across the hangers…now you are set up.
Move away from the kart, crouch down at the front and try to line the axles up. You will easily see where it’s bent as the axles will not line up with each other. To straighten it put the rear wheels back on, and put the kart on the floor.
If the right is too high then put a block of wood under the left just under the king pin, get the wife and kids to sit on the rear left and push down on the right king pin with a lever or just put some wood on it and push down with your weight.(Do not hammer it)….Keep testing until the axles line up. Hope this helps! I do it this way all the time. It’s not perfect but very close.