I.18
Part. N. 8000 A4640 (04-2005)
SOSPENSIONE ANTERIORE
FRONT SUSPENSION
SUAPENSION AVANT
VORDERGABEL
SUSPENSIÓN DELANTERA
BOZZA-DRAFT
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.
