Loosen the two bolts that hold on each of the rear swing arm covers using a socket and wrench. Remove the two covers and set them aside.
Locate the four Phillips head screws that hold the air box cover in place. Remove these screws and pull the air box cover from the bike. Use a socket and wrench to remove the two air box mounting bolts at the rear of the air box, then pull the entire air box away from the motorcycle. This will allow you to work with the rear suspension adjusters.
Turn the lower adjustment nut of both of the shock springs clockwise using a spanner wrench to tighten the shock springs. This will make the bike slightly less comfortable to ride but will make it handle better when taking corners at high speeds. Turn the adjustment nut of the shock springs counterclockwise to loosen the shock springs. This will make the bike more comfortable and give it a softer feel when cruising around town.
Replace the air box by bolting it in place with the mounting bolts and then replacing the air box cover using the four Phillips screws removed previously. Take your bike for a quick test ride and observe the action of the shocks. Return home and remove the air box once more to make any further adjustments necessary to get the maximum comfort from your bike for your riding style.
Replace the air box one final time when you are finished adjusting the shock preload. Use the bolts removed previously to reattach the swing arm cover on both sides of the bike, then go out for a ride to really feel the effects of your newly adjusted rear suspension.