Here’s how to tune your DR-Z400E & S suspension for dirt riding. This is a basic explanation of your bike: where the adjusters are and how they affect the ride. How hard and fast you ride, and how rough the terrain is, will determine where you set your adjusters. I’ve also noted where pre-02 S models lack some of these adjusters.
First, measure everything as it is adjusted now. Write it down for future reference. It’s possible that you’ll make it worse before it gets better, so it helps to know your starting points. Measure your Race Sag (next paragraph) and where your dampening clickers are currently set (the one after that).
Have you set your Race Sag? That's your preload adjustment for the shock spring, and it's pretty important. You want about 90 mm of sag with you in full gear on the bike, you'll need a friend to help measure. Changing your Race Sag will affect handling in many ways: steering, fore / aft balance, ride stiffness. Making a change of 10 mm here is huge. Good links with pictures for this adjustment procedure are at the bottom of the page. The TT store also has a Basic Suspension Setup DVD that is pretty good.
Now, what about those 5 clicker adjustments? Start by turning your clickers all the way in (clockwise), to get your starting reference point, you’ll then back them out to get the ride you want. Count the clicks as you are turning, write this number down for future reference. In is hard, stiff, harsh / out is softer, smoother, bouncier. Make your adjustments 3 or 4 clicks at a time at first, you want to make a significant enough change that you will definitely recognize what you've just done, for better or worse. Then go 1 at a time to fine tune it. You probably wish it would feel soft on small hits, but you don't want it to bottom out too often, or wallow around in sand whoops. I’ve included some suggested starting points, they are by no means where YOU should end up.
Compression adjustment for the forks is on the bottom of the legs, start with them about 12 clicks out. If your forks dive, turn them in stiffer. If too harsh, back them out. Rocks and roots will be more comfortable with them softer, but sand performance or high speeds will suffer if too soft. It's hard to get one setting that is perfect for all conditions.
Rebound for the forks is on top, dead center of the cap, start about 12 clicks out also. This controls the return stroke: too soft and the bike will bounce back or hop, too hard and the bike will feel harsh and steer funny in a series of bumps. Compression and Rebound adjustments often affect the ride in a similar fashion, making it pretty confusing sometimes to know which one needs further tuning. More on this later. Pre-02 S models have a spring preload adjuster, not rebound adjustment. The offset screw is your air bleed screw, to release built up air pressure.
Compression for the shock is a 2 part adjustment: a small screw, in the middle of a 14 mm nut, on top of the shock reservoir. These are referred to as the low speed (screw) and high speed (nut) compression adjusters. These terms refer to the shock’s rate of compression, not the speed you are going. The relationship between the high and low speed compression circuits is complicated, changing one affects the other. Set the screw about 10 clicks out, and the nut 2 full turns out. Start tuning the ride by adjusting the screw first: in if the rear is too soft on medium hits, out if the bike feels harsh and like you aren't getting full travel. (Your Race Sag adjustment, or an incorrect rear spring rate, can cause these very same symptoms, that’s why it’s so important to check them first) High speed compression is often referred to as the one you adjust to control bottoming, but it’s not that simple. Here’s the best technical explanation I’ve found: Hi / Low Speed Compression Where you ride and how you ride will determine YOUR settings, for instance many guys run the high speed nut out all the way. And you do want your suspension to occasionally bottom out on your biggest hits, but you don't want to be crushing it. Pre-02 S models only have the low speed adjuster, some frustrated tuners might call you the lucky ones.
Rebound for the shock is a screw at the bottom of the shock body, just below the swing arm. The stock valving here is a little weak for the rock ledges in the desert southwest, and I run mine at 4 clicks out. Too little rebound will cause the rear to hop up and kick you in the butt after a sharp edge hit. Too much will cause the rear to pack up, hopping side to side in the whoops (just like too much compression damping). Turn it out as much as you can, but the kicking in the butt is your tell tale sign of not enough rebound. Pre-02 S Models don’t have this adjuster.
It really helps to dedicate some time to this project. Go out with a buddy who has the same goal in mind, and go back and forth over the same terrain again and again. That way you'll really know what you just fixed, or messed up. And only change one adjustment at a time. If you do both compression and rebound at the same time, you won't really know which one just made it better or worse.
Setting your Race Sag
Checking your Free Sag and determining spring rate: Free Sag