Marzocchi Jr. T QR20 User manual

Jr. T
QR20
INSTRUCTIONS
GENERAL RULES
1. Where specified, assemble and disas-
semble the shock absorption system us-
ing M ARZOCCHI special tools only.
2. On reassembling the suspension system,
always use new seals.
3. If two screws are close one to the other,
always tighten using a 1-2-1 sequence.
In short, screw the first screw just up to the
point it is well tightened, then tighten the
second screw and then go back to the
first one and screw it tighter.
4. Clean all metal parts with a special,
preferably biodegradable solvent, such
as trichloroethane or trichloroethylene.
5. Before reassembling, lubricate all parts
in contact with each other using silicone
fat spray or a specific oil for oil seals.
6. Always grease the conic seal rings be-
fore reassembling.
7. Use wrenches with metric size only.
Wrenches with inch size might damage
the fastening devices even when their
size is similar to that of the wrenches in
metric size.

Jr. T
QR20
FAILURES, CAUSES AND REMEDIES
This paragraph reports some failures that may occur when using the fork. It also indicates possible causes and suggests a remedy. Always
refer to this table before doing any repair work.
Excessive oil build up on stanchions 1. Oil seal is worn out
2. Stanchion tube is scored
3. Excessive dirt on oil seal
1. Replace oil seal
2. Replace stanchion tube, oil seal and dust
seal
3. Clean the oil seal seat and replace oil
seal
FAILURES CAUSES REMEDIES
Oil leaking through the bottom of slider O-rings on the pumping rod bottom dam-
aged
Replace the O-rings
Fork has not been used for some time and
is locked out
Oil seals and dust seals tend to stick to
stanchion tube
Raise dust seal and lubricate stanchion
tube, dust seal and oil seal
Excessive play of stanchions into the sliders Main slider bushings are worn Replace main slider bushings
Adjuster position does not affect fork opera-
tion
Dirt inside legs Clean carefully and change oil

Jr. T
QR20
RECOMMENDATIONS FOR
MAINTENANCE
M ARZOCCHI forks are based on advanced
technology, supported by year-long experi-
ence in the field of professional mountain
biking. In order to achieve best results, we
recommend to check and clean the area
below the dust seal and the stanchion tube
after each use and lubricate with silicone
oil.
In general, M ARZOCCHI forks can offer top
performance from the start. However, in
some cases a short running-in period is
required (5-10 hours) for inner adjustments.
This running-in period will make fork life
longer and ensure fork top performance
over time.
IMPORTANT: change oil at least every
100 working hours.

Jr. T
QR20
1
11
1
INSTALLATION
Installing the fork on a bicycle is a very
delicate operation that should be carried
out with extreme care. The installation should
always be checked by one of our Technical
Service Centers.
WARNING: “A-Head Set” head-
set/Steering tube mounting and ad-
justment must be carried out in compliance
with the headset manufacturer’s instruc-
tions. Improper installation may jeopardize
the safety of the rider.
After any installation always check for the
proper torque of screws fastening stan-
chion tube onto lower crown and on upper
crown.
Have steer tube replaced at an authorized
Technical Service Centers only.
WARNING: In case of improper
installation of the steer tube into the
crown, the rider might lose control of his/
her bicycle, thus jeopardizing his/her safety.
MOUNTING THE FORK ON THE
FRAME
FIG. A
Remove the upper crown (1) from steer
tube and fork legs by loosening the 3
fastening bolts (11).
FIG. B
Assemble the fork to the frame complete
with headset. Fit the upper crown (1) into
the upper stanchions and the steer tube.

Jr. T
QR20
1
D
28
11
1
Nm 9
H
13
2828
FIG. C
The stanchions edge (28) must be aligned
with or slightly lower than the upper crown
(1).
If fork legs overprotrude, fit some spacers
(D) to the plate close to the steer tube.
FIG. D
Fit the handlebar support and the “A-Head
Set” plug over the upper crown (1) and
then adjust the steering.
Now finally tighten the 3 bolts (11) on the
upper crown to 9 Nm.
WARNING: Loosen the 3 screws
(11) on the upper crown before
adjusting the steering. Tighten the above
bolts to the specified torque when finished.
FIG. E
If the crown (13) position with respect to
the stanchions (28) has been changed for
any reason, adjust the original distance.
– Distance H between crown and tyre
edge (when inflated) should not be lower
than total travel (170 mm or 150 mm)
+ 3 mm.
WARNING: If lower Crown is im-
properly matched with stanchions, it
may touch the tyre and cause severe inju-
ries to the rider.

Jr. T
QR20
15
Nm11
Nm6
BD
B
C
A
A
C
FIG. F
Tighten the 4 stanchions fastening screws
(15) onto the crown to 11 Nm.
WARNING: do not overtighten the screws
holding the stanchions to the crown as this
may distort the stanchions and weaken the
whole structure.
After any installation always check for the
following.
Proper torque of bolts fastening stanchion
tube onto lower crown (11 Nm) and upper
crown (see FIG. D).
FRONT WHEEL ASSEMBLY
IMPORTANT: fixing the front wheel prop-
erly as specified in the instructions given
below is essential for the proper operation
of this fork and all related devices, and
therefore for safe riding. You are advised to
follow these instructions closely.
Slacken the lock nut of the quick release lever
so the hub will fit between the fork sliders.
Make sure the quick release bushings (A)
are centered to the recesses in the sliders.
Lock the quick release lever (B) and make
sure the bushings (A) are properly seated
in the sliders.
Fit bolt end (C) in suitable slider groove and
tighten the screw (D) to specified torque.
WARNING: These sliders are spe-
cifically designed to fit this type of
hub. Do not use any hub design other than
that specified here, as this would not ensure
proper fastening of the wheel and may lead
to breakdown of the assembly components.
DISC BRAKE SYSTEM ASSEMBLY
Assembling the brake caliper onto the slider
is a very delicate operation that should be
carried out with extreme care.
Improper assembly might overstress the
caliper supports which might break.
When installing the disc brake system, be
sure to properly follow the instructions given
by the manufacturer.

Jr. T
QR20
2
C
ADJUSTMENT
SPRING PRELOAD
Spring preload can be adjusted by turning
the knob (2) on the top of the fork legs. From
the factory the fork is set at minimum preload,
i.e. the adjustment knob completely un-
screwed counterclockwise. However,
springs are slightly preloaded to counteract
static loads during COMPRESSION. By
turning the adjuster knob clockwise, the
preload is increased up to the maximum
value equal to 15 mm spring preload. This
adjustment is essential in order to have the
right fork response for the rider’s weight
and riding style.
REBOUND DAMPING ADJUSTMENT
The adjuster controlling REBOUND damp-
ing adjustment is accommodated inside
cartridge rod (27) inside each fork leg.
To access the adjuster, unscrew the top caps,
push the stanchions fully down and take the
washer and preload sleeve out (see section
DISASSEMBLY, Fig. 1 and 2)
WARNING: Do not remove the
springs or this will alter the amount of
oil inside the fork legs.
Insert supplied hexagonal rod (C) in the
stanchion tube and rod edge into adjuster
hexagonal hole.
Rotate the adjuster clockwise for harder
damping, counterclockwise to soften it.
Refit the preload sleeve, washer and cap.
Tighten cap to the specified torque (see
section REASSEMBLY, Fig. 24 and 25).

Jr. T
QR20
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DISASSEMBLY
GENERAL
– The reference numbers given in this section relate to the components shown in the fork exploded view.
– Operations refer to the fork legs already removed from the upper crown and from the crown.
– Before starting any operation. please read the diagram below. It shows the quickest procedure and the exact disassembling sequence.
Locate the part you need to remove in the diagram, then look at the arrows to determine which other parts you need to remove first.
DISASSEMBLY DIAGRAM
SPRING FIG. 2
FOOT BUFFER FIG. 10
CARTRIDGE ROD FIG. 10
FOOT NUT FIG. 3
STANCHION TUBE CAP FIG. 1
DUST SEAL FIG. 5
STOP RING FIG. 6
OIL SEAL FIG. 7
CARTRIDGE ROD CHANGE
VALVE ASSEMBLY CHANGE
STOP RING FIG. 11
VALVE ASSEMBLY FIG. 11
GUIDE BUSHING AND SEAL
ASSEMBLY CHANGE
SPRING CHANGE
REBOUND SPRING FIG. 10
STANCHION TUBE FIG. 4
UPPER WASHER FIG. 8
GUIDE BUSHING FIG. 9

Jr. T
QR20
SPRING CHANGE
FIG. 1
Place the stanchion tube (28) in a vice. Be
sure not to damage or squeeze stanchion in
the process. Unscrew the plugs (5) with a
26 mm hexagon wrench.
Remove the plugs complete with the O-ring
(6) from the stanchions.
FIG. 2
Push the stanchion tube into the slider and
remove the upper washer (9), the preload
sleeve (16), the spring (17), the retaining
ring cap (34) and the spring (37).
Make all necessary changes.
5
6
28
39
GUIDE BUSHING AND
SEAL ASSEMBLY CHANGE
FIG. 3
Let all the oil drain out.
WARNING: Remember to always
recycle any used oil.
To change the fork leg oil follow the proce-
dure as described in section “REASSEMBLY”
from Fig. 22 to Fig. 25.
Turn the fork leg upside-down and unscrew
the foot nut (39) by the use of a 15 mm
socket wrench.
17
37 34
9
16

Jr. T
QR20
28
24
19
20
GUIDE BUSHING AND SEAL
ASSEMBLY CHANGE
FIG. 4
Pull the stanchion tube (28) completely out
of the slider (24).
FIG. 5
Remove the dust seal (19) from the top of
the sliders using a small screwdriver.
FIG. 6
Remove the stop ring (20) from the sliders
by placing the screwdriver bit in one of the
three openings on the stop ring.
IMPORTANT: when removing the stop
ring, make sure not to damage its seat.

Jr. T
QR20
21
A
22
23
FIG. 7
Fit the slider protector (A) onto the slider
and remove the oil seal (21) with the help
of a large screwdriver.
IMPORTANT: when removing the oil seal,
make sure not to damage its seat. Once
removed the oil seals should not be used
again.
FIG. 8
Remove the upper washer (22) from the
slider.
FIG. 9
Fit the bit of a small screwdriver into upper
edge slot of the pilot bushing (23) and lift
gently. Pull the bushing out of the slider and
make all necessary changes.

Jr. T
QR20
18
26
27
18
(150) (170)
26
27
3132
30
47 46 38 29
REPLACING PUMPING ELEMENT
SEALS
FIG. 10
Remove the foot buffer (31) complete with
ring (32) from the pumping rod (27) end.
Slide out the pumping element (27) and the
rebound spring (26) from the stanchion
tube top and let them travel 170 mm, or
slide out the two springs (26) for a travel
of 150 mm. Replace the seal ring (18) if
damaged or worn out.
VALVE ASSEMBLY CHANGE
FIG. 11
To check that the valve assembly is operat-
ing correctly, it is necessary to work on the
inside of the stanchion tube.
Slip off the stop ring (30) using pointed
pliers.
Pull the valve assembly out of the tube with
one finger in this sequence: covering (47),
valve (46), rebound spring (38) and washer
(29).

Jr. T
QR20
23
22
21
B
REASSEMBLY
CAUTION: before reassembling, all metal
components should be washed carefully
with inflammable, preferably biodegrad-
able, solvent and dried with compressed
air.
PILOT BUSHING AND SEAL
ASSEMBLY
FIG. 12
Check that no dirt or debris is between
slider and bushing. Insert the pilot bushing
(23) into place so that it adheres to the
slider.
FIG. 13
Fit the upper washer (22) into the slider so
that it touches the pilot bushing.
FIG. 14
Lubricate the oil seal (21) and place it onto
the seal press (B) with the hollow side
toward the slider.
Press the oil seal until it touches the lower
washer by using the above seal press.

Jr. T
QR20
20
19
26 47
18
29
38
46
(170) (150)
27
26
18
27
FIG. 15
Insert the stop ring (20) into the slider
making sure it is properly seated into place.
Use buffer (B) to properly seat the ring into
the slider.
FIG. 16
Lubricate the dust seals (19) and fit them
into the stanchions from the spring end.
VALVE AND PUMPING ROD
ASSEMBLY
FIG. 17
After having overhauled or replaced the
valve unit and after having cleaned the
inside of the stanchion tube, reassemble.
Assemble valve components, in correct se-
quence: washer (29), rebound spring (38),
valve (46) and covering (47).
Then fit pumping rod (27) with seal ring
(18) and a rebound spring (26) if travel
is 170 mm or two rebound springs (26)
if travel is 150 mm into the valve assem-
bly.

Jr. T
QR20
31
32
27
25
30
D(150)
(170)
D
28
19
FIG. 18
Lubricate O-rings(25) and (32) and reas-
semble the foot buffer (31) onto the end
part of pumping rod (27).
FIG. 19
Fit this assembly into the stanchion tube and
properly seat the valve assembly (D).
Insert the stop ring (30).
STANCHION TUBE ASSEMBLY
FIG. 20
Fit the stanchion tube (28) gently into the oil
seal (21), together with dust seals.
Rotate the stanchion tube while inserting it
into the seal to reduce the chance of dam-
aging the seals.
Turn the slider over and check that cartridge
thread (27) is sticking out through the slider
hole.
Check to see that the stanchion tube slides
unrestricted by cycling the fork up and
down several times.
The tube should slide freely inside the seal
assembly without any side play.
In the event it is too hard or too soft, repeat
the previous steps described above and
check components to ensure they are not
damaged.
Seat the dust seal (19) on top of the slider.

Jr. T
QR20
39
Nm 11
100
17
37
34
FIG. 21
Screw the foot nut (39) onto pumping
element thread (27).
Tighten to 11 Nm.
Pump stanchion up and down several times
to make sure it slides properly through the
stroke.
HOW TO FILL WITH OIL
FIG. 22
Pour the oil little by little when the stan-
chions are fully down and then pump stan-
chion tube up and down so as to have a
better filling.
Check that the oil level is 100 mm from the
top of the stanchion tube, in both legs.
SPRING AND PRELOAD CAP
FIG. 23
Fit the spring (37), the retaining spring cap
(34) and the spring (17) into the stanchion
tube.

Jr. T
QR20
9
16
Nm20
5
6
FIG. 24
Fit the preload sleeve (16) and the top
washer (9) into the stanchions.
FIG. 25
Lubricate the O-ring (6) on the cap (5).
Turn the plunger (8, see exploded view)
inside the cap counterclockwise until it is at
its minimum setting.
Assemble cap, together with O-Ring (6),
onto stanchion tube by hand. Tighten to 20
Nm.
Install fork legs into crown and upper crown
as specified in section “INSTALLATION”.