Husqvarna 2004 CR 250, Workshop Manual

Page: 232 / 364

I.24
N° 8000A2954 (09-03)
FRAME, SUSPENSIONS AND WHEELS
FORK WORKING
The hydraulic system of this fork relies on multivalves; a system already tested in
the past MAGNUM but with different features as both legs have the same setting.
Therefore, each leg represents a complete suspension system to be considered as
such when adjusting.
In order to give a better explanation on how the suspensions work, the moving
parts (dark background), dependant on the wheel, are different from the parts
fixed to the motorbike frame (light background); any oil flowing or movement in
the different working stages is represented by means of arrows (see FIG. 1).
The moving part of each leg is formed by a stanchion (1) secured to the slider 2);
having inside a foot valve (3) equipped with a piston (4) with washers and a
compressor screw adjuster (5). The cartridge body (6) is secured inside the
stanchion.
Parts fixed to the frame consist of an outer slider (7) closed at the top by the plug
(8). The inner pumping element (10) of the cartridge (6) is secured to the upper
plug (8) of the stanchion tube by means of a rod (9). A rebound screw adjuster
(11) located on the plug operates an inner push-rod (12) that in turn displaces a
conical pin (13) placed right on top of the pumping element.
The lubrication of the sliding bushings (14 and 15) and the seal ring (16) is
guaranteed by the fluid into the chamber between the stanchion tube (1) and the
slider (7). The oil flows into this chamber through two big holes on the stanchion
top (1), just under the bushing (15).
Turn the screw adjusters (5 and 11) to set the fluid flowing outlet, in this way the
suspension response during compression and/or rebound can be changed. Each
adjustment will “click” in position.
Always start with max. damping position (adjuster completely screwed clockwise)
for any adjustments. Small damping increments will produce big effects if made in
both fork legs.
Let’s see what happens in each leg during COMPRESSION (see FIG. 2).
The oil into the cartridge is compressed by the movement of the pumping element
(10) and can flow only through the holes in the piston (4) and the middle groove
of the foot valve (3).
This passage is adjusted by the action of the washers (A), under the piston, and
the position of the conical pin of the screw adjuster (5).
In order change the fork damping at this stage, apart from turning the screw
adjuster (5), also change the washer setting (A) by using washers of different
thickness and diameter among the available ones.
In this phase, some oil, flowing through the open channels of the pumping
element (10) wins over the action of the upper return spring (17) and, lifting the
washer (18), compensates the inlet volume in the cartridge.
The oil coming out of the cartridge then flows into an outer chamber
communicating with the depressurized leg top (see FIG.3A).
The chamber and the leg top are linked together thanks to the passage areas
between body plug (19) and stanchion (1) and four big holes on the body plug
top.
The rebound bumper (20) is on the rod (9). It has a special outer floating ring,
which in case of very hard compressions (see FIG. 3B), apart from working as
end of stroke for the fork leg, closes the four oil holes of the body plug (19), thus
slowing down the rod compression to a greater extent.
FIG.2
FIG.3A FIG.3B
I-2-WR CR 250-2004 11-09-2003 16:14 Pagina I.24