And if Rods suggestion doesn’t work, take that big screwdriver and put it at about a 45° angle (maybe greater) at the end of the ‘split’ in the hub. Tap it lightly with a hammer to try and motivate the hub off the axle. Again, don’t get too carried away as you could damage the hub/axle. Try to keep the screwdriver as square on the end of the split as possible and avoid the axle. You can also try using a rubber mallet at the ends of the hubs if you don’t want to risk things with a screwdriver.
By ‘narrow/wide’ bearings, do you mean diameter? All you really ever see are 40mm and 50mm axles unless you’re dealing with kid karts. 50mm is roughly 2inches in diameter. If the kart is newer (within the last 5 or 6 years), then I’m willing the bet it has a 50mm axle.