This is the most fundamental part of kart setup. It is essential to have correct camber, caster and tracking but before checking any of these things you need to be sure the chassis is straight.
It's worth making a couple of simple checks before you do anything else.
First - is your chassis square? You can check this by measuring from the front of the axle to the back of the king pin on each side; both side should be within 2mm. A better check, but it means removing the engine and seat, is to measure diagonally between a fixed point on the rear bearing hanger and the king pin on the opposite side; again the 2 diagonal measurements should be within a couple of millimetres.
The next check is to ensure the front and rear of the chassis are level. You will probably need to remove the sidepods and possibly the engine. With the kart on a stand or trolley remove the wheels and hubs then put a straight edge across the 2 king pins - a spare axle or a long spirit level is ideal for this - you may meed someone else to hold it. Then stand or kneel in front of the kart so your eyes are at axle height about 6 or 8 feet away. You should be able to gauge the alignment between your straight edge and the rear axle by eye. With practice it's possible to get this within a fraction of a millimetre.
If you can afford it there are tools to help you do this; some laser systems have the capability for checking front-to-rear but rely on the front laser being absolutely level to project a beam onto the rear axle, because the level is working in a different axis to the comparison you wish to make any inaccuracy in the level is multiplied by the distance from front to back. A better way in our opinion is to use 2 levels in the same axis. A Wildkart axle level is mounted in a magnetic 'V' block which fits onto the rear axle; the chassis then needs to be shimmed up on the trolley until it is perfectly level. Then put a standard builder's spirit level across the king pins; this should now indicate level, if not the chassis will need correction.