Install the Correct Rear Spring
The KLX handles well right out of the box, but anybody over 135 pounds will find it too soft in the front, and anybody under 185 pounds will find it too stiff in the rear. And the best way to determine the correct spring for your weight and riding style is to measure and adjust Sag. Once you've got sag correct, then you can fine tune your KLX with... Dampening Adjustments
Scenario #1 => You adjusted the shock preload for the correct Rider Sag, then measured a Bike Sag of less than 25mm. This means your spring is too soft for your riding weight. Yeah, it sounds backwards, but here's what happened: to get your Rider (Race) Sag correct, you set the preload higher than it would have been with the correct (stiffer) spring. So the bike sags less than the recommended value under its own weight.
Scenario #2 => You adjusted the shock preload for the correct Rider Sag, then measured a Bike Sag of more than 35mm. This means your spring is too stiff for your riding weight. Here's what happened: to get your race sag correct, you set the preload lower than it would have been with the correct (softer) spring. So the bike sags more than the recommended value under its own weight.
And here's the fix for either case => goto... RaceTech.com and checkout the recommended spring rates for your bike, riding style and riding weight. Buy the spring and install it, then recheck your Rider and Bike sag, and adjust as necessary. Here's how to get that new spring installed...
Remove the swingarm with Service Your Swingarm
Remove the lower shock mounting bolt
Swing the shock toward the rear of the bike
[or remove side panels, seat & upper mounting
bolt, then remove the shock from the bike]
Lubricate the threads on the shock body
Loosen the preload adjusting rings
Move both to the top of the shock body
Remove the lower retaining cup
(don't scratch the shaft!)
Pull the old spring off & install the new one
Put everything back together again
Re-adjust your preload with Sag Adjustments
Fine tune with Dampening Adjustments