FORK_VALVING

This is the DRZ-E MODIFIED fork compression shim stack:

Piston
1) 24 x 0.1 with straight cut on the border, 13.5 mm long, aligned with one piston hole
2) 24 x 0.1 3) 24 x 0.1 4) 24 x 0.1 5) 24 x 0.1 6) 24 x 0.1 7) 24 x 0.1 8) 22 x 0.1 9) 20 x 0.1 10) 18 x 0.1
11) 16 x 0.1 12) 14 x 0.15 13) 12 x 0.2 14) 9 x 0.2
N.2 clamp shim 10 mm

Oil: Putoline Fork oil SAE 5 or equivalent. BEWARE: using higher SAE grade oils the bleeding area dimension must be increased.
The bleeding area in the first shim has two effects:

1) Excellent damping of small terrain roughness at low bike speeds (= good)

2) Reduced sensitivity of the regulating screw (= bad)

Someone could like more damping at high (piston) speeds: this can be achieved by substituting some 24 x 0.1 shims with 24 x 0.2 or 24 x 0.15 shims, and/or subtracting some little shims, starting from the 9 x 0.2 . Remember that the whole stack thickness cannot come down the stock value too much. Remember, also, that placing one shim instead two, having twice tickness (i.e. the total thickness is the same), the shim stiffness is 4 times bigger. Remember that the stack blocking nut must be tightened very little, to avoid the axle cracking!!! In reassembling, don't use the impact wrench: a manual wrench is better.

With this stack I have seen a big improvement in the fork behaviour in every condition, although more high speed damping could be useful, expecially for the heavier riders.

3) SUZUKI DRZ 400 E FORK VALVING

Stock extension stuff if ok. Unlike, there is a problem within the compression assembly: the bleeding hole in the center of the aluminium axle, that is occluded by the regulation needle to tune the low speeds damping, is too small. The regulation of the low speeds is not so effective as we expect.
There is no way to improve this performance, because a bleeder shim will increase the bleeding area too much, and an increased hole diameter could cause a weakness of the aluminium axle of the stack. A good idea could be to install aftermarket base valves, although I haven't tested it: probably they fix this problem.
For who want to fix the problem by himself, in the following there is the modified stack.

This is the STOCK DRZ-E fork compression shim stack:

Piston
1) 24 x 0.1 2) 24 x 0.1 3) 24 x 0.1 4) 24 x 0.1 5) 24 x 0.1 6) 24 x 0.1 7) 15 x 0.1 8) 24 x 0.1 9) 22 x 0.1
10) 20 x 0.1 11) 18 x 0.1 12) 16 x 0.1 13) 14 x 0.15 14) 12 x 0.2 15) 9 x 0.2
N.2 clamp shim 10 mm

It's very stiff at low speeds, and soft at high speeds: the flaws reported by everyone that has tested the stock drz-e fork.

I've tested one fork leg without the spring, in order to evaluate the beahaviour of the compression stack. The correct damping should be proportional to the relative speed of the two elements of the fork leg. The result was:

- At low speeds the damping is too much, for every position of the regulating screw.
- At high speeds the damping is too few.

The first problem is due to a Showa error in designing the compression assembly. The only chance is to add a bleeding hole in some way. I decided to cut away a piece of the first shim border, with a straight cut. The cut line lenght is 13.5 mm, and this cut must be aligned with one piston hole. Rotating the cut from this centered position, the bleeding area can be reduced, if necessary. The cut can be carried out by a grinding tool, and finished with grinding paper. Be careful: don't over-heat the shim!

If it's the first time that the base valve is dismounted, it's better to use an impact wrench (the base valve is very tight), or follow the procedure to dismantle the leg (you can find it in various websites).
If isn't the case, follow this: while a person push down the leg, another person will unscrew the base valve. After some turn, push the plate outside the base valve, otherwise it will raise. Unscrew completely the base valve and dismount.