The rear shock is pretty simply to setup, but there are lots of different opinions on the process. Here is what I do:
1. The first thing you need to do is to set your static sag. The is the amount of drop you bike has when going from a stand to resting on the tires. The process is simple. Place the bike on a stand, and measure from the axle nut straight up to a spot you have marked on the rear fender. Write this number down. Take the bike off the stand, and push down on the seat a couple of times. While a friend holds your bike at the handle bar (with no pressure on the seat), measure the distance from the axle nut to the same spot on the rear fender. Write this number down, and compare it to your first number. You should have a difference between 7/8 inch and 1 1/8 inch. I put the range, as some folks believe it should be spot on one number or another, but unless your an expert level racer, you probably will not feel the differenct. If the difference is more or less than this, tighten or loosen the spring nut to adjust the static sag to the proper setting.
2. Put on your riding gear on. Mount your bike
, and stand in your normal riding position. Have your friend measure the distance from the axle nut to the same spot on the rear fender. Compare this number to the first number (the one you measured while the bike was on a stand), this is your race sag. Your race sag is somewhere between 3 3/4 inches, and 4 1/4 inches. Here again, I list a range, as some folks believe that it should be spot on 4 inches. However, a range works for most good trail riders. If the your race sag falls outside this range, you will probably be well served to replace the spring with one that is better suited to your weight. Some folks will just change the spring nut settings, but this is far from the the best method. For the $80 you will spend on the correct rear spring, you will enjoy the ride a lot more.
3. Once your spring is setup and properly sized for your weight, you need to adjust the clickers. You have two adjustments, one at the top of the shock, and one at the botton. The top adjustment changes compression, while the bottom changes rebound. Ironically, you can change the rebound "feel" by changing the compression and visa-versa, so it takes a little time to dial in a shock.
4. To start adjusting the clickers, turn each adjustment screw in all the way (do not tighten too much, just screw in until it stops), and then count the number of clicks as you turn the screw full out. Once you know the total number of clicks, put each screw right in the middle by counting the clicks from all the way in.
5. Go out to your favorite riding area, something with which you are familiar. Select a section of trail (maybe 2-3 miles long) that has varying terrain. This is your test section. Ride your test section a few times, paying attention to the feel of the rear end. If you are unhappy (which you most certainly will be), try and define why and where you are unhappy. For instance, in the big whoops, does the bike have too much rebound, or not enough compression dampening. With this insight, change one of the clickers only. For instance, if you don't like the rebound , turn the bottom screw in 3 turns and go for another ride. If things get worse, return the screw to the middle, and turn it our 3 turns. Go for another ride. If things get better, but still not there, try a couple more turns. If things get worse go back one at a time until you find the best setting. Now turn you attention to the other screw, and perform the same trial and error. Don't be afraid to return both screws to the center, and start your testing again, this time starting with compression adjustment.
Suspension tuning is very personal, so no one can do it for you. It also takes some time to fine tune your ride. You will have to make some compromises to get the best ride in different terrain, so take your time and get it setup just right.
Good luck
Rick