How to set up your Dirt Bike Suspension
Taking some time to learn about and set up your dirt bike suspension costs nothing, and can really improve your lap times.
The first thing to do when setting up your dirt bike suspension is to put the rebound and compression clickers for both the forks and rear shock in their standard position (check owners manual for how many clicks out is standard), if you don't have manual just set them halfway between hard and soft.
To set the static sag on the rear shock you first need to set the preload. Back off the locking ring and then you either tighten or loosen the main ring to increase or decrease the preload on the shock. Put the bike on a stand with the rear wheel off the ground and measure from the axle nut to a point roughly above it on the bike (say, a mounting bolt for the muffler or a part on the rear subframe), now take the bike off the stand and let it stand upright. With the bike off the stand now measure the distance between the axle bolt and the point on the bike itself. Subtract that measurement from the distance measured when the bike was on the stand, there should be about 25mm of sag, if there's more than that wind up the preload or if there's less then back it off. this measurement is called static sag.
Now to set the laden sag (race sag). Take note of the measurement with the bike standing upright. Now with all your riding gear on sit on the bike in the attack position (head roughly over the crossbrace, elbows up and out and feet on the pegs), have someone hang onto the bike for you and take a measurement again. The amount of sag should be between 90mm and 110mm, again if its more or less then adjust the preload ect.
Your should be able to get it set up approximately to those figures, if it's way out on either then that can indicate that it either has different springs than standard (if you bought the bike secondhand) or that your're heavier or lighter than the model used by the bike manufacturers. They base their settings on a theoretical rider who is about 5'10" tall and about 180 lbs.