SHERCO ST Series Instruction manual

ST SERIES

1

1
TABLE OF CONTENTS
FOREWORD .................. Erreur ! Signet non défini.
ST SERIES TOOLS LIST .. Erreur ! Signet non défini.
TECHNICAL SHEETS ...... Erreur ! Signet non défini.
ENGINE ............................................................... 4
CYCLE PARTS .................................................. 5
ORIGINAL SETTINGS ...... Erreur ! Signet non défini.
CARBURETOR ..................................................... 6
FRONT FORK....................................................... 7
REAR SHOCK ................ Erreur ! Signet non défini.
CYCLE PARTS ..................................................... 8
FRONT ................................................................ 8
1.1 Wheel bearing repla ement ............................................ 8
1.2 Dis repla ement ......................................................... 8
1.3 Fork disassembly ......................................................... 9
1.4 Fork maintenan e ...................................................... 10
REAR ................................................................ 13
2.1 Wheel bearing repla ement ......................................... 13
2.2 Dis repla ement ....................................................... 13
2.3 Swingarm bearing ontrol ............................................ 14
2.4 Control of links ........................................................... 15
OPERATIONS REQUIRING REMOVAL OR NOT OF
THE ENGINE ............................................................. 16
ENGINE REMOVAL / ASSEMBLY .................. 17
ENGINE REMOVAL ......................................... 17
ENGINE ASSEMBLY ....................................... 17
DISASSEMBLY OF THE ENGINE ................... 18
❱❘ Oil draining ............................................................. 18
❱❘ Removal of pinion and sele tor .............................. 18
❱❘ Removing the ylinder head, ylinder and piston .. 19
❱❘ Removing the lut h over ..................................... 20
❱❘ Clut h and primary gear removal ........................... 21
❱❘ Ki k removal ........................................................... 21
❱❘ Removal of the sele tion ........................................ 22
❱❘ Removing the ignition ............................................. 23
❱❘ Intake pipe and reed box ........................................ 23
❱❘ Removal stator ....................................................... 24
❱❘ Separate the rank ase ......................................... 24
❱❘ Removing the gear box .......................................... 25
❱❘ Removing the onne ting rod assembly ................ 26
ENGINE ELEMENT CONTROL ....................... 27
❱❘ Balan e weight, external dimension ontrol ........... 27
❱❘ Conne ting rod radial learan e ............................ 27
❱❘ Conne ting rod head side play ............................... 27
❱❘ Crankshaft runout ontrol ....................................... 27
❱❘ Piston ..................................................................... 28
❱❘ End gap .................................................................. 28
❱❘ Piston pin he k ..................................................... 28
❱❘ Piston / ylinder ondition he k ............................ 29
❱❘ Reed box, inlet pipe ............................................... 29
❱❘ Clut h ..................................................................... 30
❱❘ Clut h dis ontrol .................................................. 30
❱❘ Gear box ................................................................. 31
REASSEMBLING THE ENGINE ...................... 32
❱❘ Assembly of rank ase .......................................... 32
❱❘ Ignition assembly ................................................... 32
❱❘ Sele tion me hanism ............................................. 33
❱❘ Ki ker shaft mounting ............................................. 34
❱❘ Primary transmission and lut h ............................ 34
❱❘ Clut h over ........................................................... 36
❱❘ Water pump over .................................................. 36
❱❘ Piston / ylinder ..............E eu ! Signet non défini.
❱❘ Squish tabke setting ............................................... 37
❱❘ head ylinder .......................................................... 37
❱❘ Reed box, inlet pipe ............................................... 38
❱❘ Front sproket .......................................................... 38
TIGHTENING TORQUES TABLE ....................39
ELECTRICAL PART ........................................40
❱❘ Ele tri al omponents ............................................ 40
❱❘ Ignition stator ontrol .............................................. 41
❱❘ Hall sensor ontrol ................................................. 41
❱❘ Regulator ................................................................ 41
❱❘ CDI ......................................................................... 42
❱❘ Ignition oil ............................................................. 42
❱❘ Temperature sensor ............................................... 43
❱❘ Fan ......................................................................... 43
ELECTRIC DRAWING .....................................44
❱❘ Homologated light harness .................................... 44
❱❘ Racing light harness ............................................... 46
❱❘ Principal harness ..................................................... 47

2
ST SERIES
FOREWORD
This manual is primarily intended for qualified me hani s working in a properly equipped
workshop.
The exe ution of the various operations requires solid me hani al knowledge and SHERCO
tools spe ifi FOR the 125/250/300 ST engines.
This workshop manual omplements the user manual for SHERCO 125/250 and 300 ST.

3
ST SERIES
ST SERIES TOOLING LISTING
Tools Refe ences Designation
R172 Clut h lo k
2080 Water pump bearing tool
2074 Starter shaft seal tool
R232 Water pump tip tool
R465 Barrel bearing tool
2073 Spring blo k (sele tion finger)
1821 Engine support
R075 Magneti flywheel puller
R481 Servant

4
ST SERIES
TECHNICAL SHEET
ENGINE
125 250 300
Types Mono- ylinder 2 Stroke liquid ooled
Displacement 123,70 249,70 294 CC
Bo e / St oke 54X54 mm 72,8X60 mm 79C60 mm
Fuel Lead-free with an o tane rating of at least 98 mixed with 2-stroke oil (2%)
Cooling Liquid with for ed ir ulation
Ignition Hidria Digital
Spa k plug W16EPR-U3021
Distance between
spa k plug elect odes 0.7 mm
Piston Aluminum foundry with graphi pro essing
Engine oil 580 ml ATF type
P ima y t ansmission 20X76 24X70 24X70
Gea box 5 gears
1st 13 : 33
2nd 15 : 35
3 d 18 : 33
4th 24 : 26
5th 31 : 20
Final t ansmission 9 X 42 9 X 44 9 X 44
Clutch Diaphragm system, hydrauli ontrol
Sta te Retra table gear and ki k system

5
ST SERIES
TECHNICAL SHEET
CYCLE PARTS
F ame
Tubular steel in Chrome
-
Molybdenum
F ont fo k Fork Te h 39mm Aluminum (Fa tory) / Steel(Ra ing)
Rea shock
Hydrauli rear sho k Reiger 2way (FACTORY)
Hydrauli rear sho k R16V (RACING)
Aluminium swing arm
Fo wa d / eve se st oke FACTORY 165/175mm
RACING 165/175mm
F ont b ake Dis Ø 185mm
Rea b ake Dis Ø 145mm
F ont ti e 2,75-21’’
Rea ti e 4,00-18’’
Ti e p essu e 0.4/0.3 bar
Fuel capacity Capa ity 2,4L
Wheelbase 1322mm
Weight 68 kg

6
ST SERIES
ORIGINAL SETTINGS
CARBURETOR
125 250 300
Ca bu eto type KEIHIN 28 KEIHIN 28 KEIHIN 28
Needle position P5 P2+0.5 P4+0.5
Needle JJH JJH JJH
Main jet KEA 122 KEA 125 KEA 125
Idle jet KEP 50 KEP 45 KEP 45
Ai sc ew position Between 0.5 et 1 turn
Between 0.5 et 1 turn Between 0.5 et 1 turn
Sea level
Settings
125
250
300
More
to
2 000 m
Air screw
Idle jet
Needle
Needle position
Main jet
O.5 TO 1
55
JJK
4
118
0.5 TO 1
48
JJK
4
120
0.5 T0 1
48
JJK
4
120
2 000 m
to
1 000 m
Air screw
Idle jet
Needle
Needle position
Main jet
0.5 T0 1
55
JJJ
4
120
0.5 T0 1
48
JJJ
4
122
0.5 T0 1
48
JJJ
4
122
0m
to
1000 m
Air screw
Idle jet
Needle
Needle position
Main jet
0.5 T0 1
50
JJH
5
122
0.5 T0 1
45
JJH
4
125
0.5 T0 1
45
JJH
4
125

7
ST SERIES
ORIGINAL SETTING
FRONT FORK
Settings – Fork Te h 39mm
Sp ing p eload
Starting from the fully open position,
turn 5.5 turns
Extension
Starting from the fully losed position,
open 19 li ks
Limit adjustment
Starting from the fully losed position,
open 2.5 turns
Hyd aulic comp ession
Starting from the fully losed position,
open 1.75 turns
Left a m oil level
130 mm
Right a m oil level
75 mm
REAR SHOCK
Settings Facto y – sho k REIGER
Sp ing
65 N/mm
P eload sp ing
7.0mm +/- 0.8mm
Rest icto
1.55 mm
Rebound
32 li ks open 50 li ks max.
Setting Racing – Sho k OLLE
Sp ing
6.2kg/mm

ST SERIES
CYCLE PARTS
❱❘ FRONT
1.1 Replacement of wheel bearings
• Loosen the lo king s rew lo ated on the
right tube.
• Loosen the axle, using a BTR key and
remove it.
• Take out the wheel.
Front wheel axle tightening : 100Nm
• Use a heat gun to heat the bearing
surfa e on the hub .
• Remove the bearings using a flush
valve and then repla e them with new
ones, referen e 0175.
1.2 Front disc replacement
• When repla ing the front brake dis ,
apply when reassembling the Lo tite
243 and on the s rews and tighten to a
torque of 12Nm
• Pro eed in the reverse pro ess and
lightly grease the front axle.
WARNING
Before any operation, make sure that the motor y le is properly fixed
and that it annot fall
WARNING
Using a aliper, he k the size of the internal spa er referen e 5930 on the front wheel
and repla e it if ne essary.
Minimum toleran e
:
67.5mm

9
ST SERIES
CYCLE PARTS
1.3 Disassembly of the for and replacement of the bearings
• Remove the two M8 s rews [1] and
remove the aliper.
Calipe sc ews : 24 Nm
• Che k the thi kness of the brake pads.
Tolerated limit : 1mm
• Loosen the 4 M8 s rews of the
handlebar holder then remove the
handlebars.
• Loosen the steering olumn nut [2], the
M8 s rews [3] of the upper triple lamp
then remove it.
• T iple clamp sc ew : 24 Nm
• Loosen the steering olumn lo k nut [4] and its dust over, then separate the omplete
Fork of the frame
• Repla e the bearings lo ated in the upper part of the frame and on the part lower of the steering
olumn [5] by brand new referen e C009 taking are of grease them.
• When reassembling, install the steering olumn lo k nut and tighten it so that that the fork turns
freely and without hard point. Then pla e the top triple lamp and tighten the upper steering
olumn nut to 20 Nm.
2
1
2
1
3
4
5

10
ST SERIES
CYCLE PARTS
1.4 TECH for maintenance
1.4.1 Right side oil change
• Pla e the fork tube in a vi e with a
suitable support so as not to damage it.
• Using a 17mm wren h, loosen the
plug.
• Remove the plug [1] from the fork tube
so that you have a ess to the nut [2]
• . Hold the plug [1] and loosen the nut [2]
using a 14mm wren h
• . Remove the plug from the diving tube.
• Hold the rod inside the axle [3] then
empty the oil in a ontainer by moving
ba k and forth as shown in the photo.
• Pla e the suspension arm verti ally and pour 250 of new oil inside.
WARNING
Servi e the fork every 20 hours or every 6 months
WARNING
Use oil type SAE 5.
1
2
3

11
ST SERIES
CYCLE PARTS
• Perform an up and down movement as
shown in the photo so the hydrauli
system has primed. Stop when you feel
slight resistan e.
• Compress the tube and the rod to the
maximum stop.
Measure the oil level from the top of the
tube, top up until you rea h the desired
value.
Oil level : 75mm
• Uns rew the diving rod nut as mu h
as possible and install the plug.
• Tighten the plug [4] with the nut [5] to
a torque of 12Nm
• Tighten the plug on the tube to a
torque of 12Nm
1.4.2 Oil change on the left side
• Uns rew the ap [6] using a 17mm
wren h.
• Remove the tapered spa er [7] .
4
5
6
7

12
ST SERIES
CYCLE PARTS
• Remove the spa er [8] and the
washer between it and the spring
.
• Take the spring [9] out of the fork
tube, taking are to dry it with a loth.
• Drain the oil from the fork tube.
• Fill the arm with 250 of new oil.
• Pump the tube several times then pla e
it in the maximum ompression
position.
• Measure the volume from the top of the
tube and top up with oil until you rea h
the desired level.
Oil level : 130mm
• Reassemble in order, the spring, the washer, the spa er, the oni al spa er then the top ap
• Pla e the fork in a vi e using a
prote tion for the tube and tighten the
plug to 12N m.
8
9

13
ST SERIES
CYCLE PARTS
❱❘ REAR
2.1 Replacement of wheel bearings
• Hold the wheel axle on the left side and
loosen the nut on the right side
• Remove the axle from the left.
• Take out the wheel and remove the
spa ers.
Rea wheel tightening : 100 Nm
• Heat the hub at the bearing seat
using a heat gun.
• Extra t the bearings using a ø 20
flush.
• Repla e the bearings with new ones,
referen e 0175.
2.2 Disc replacement
• When repla ing the rear brake dis ,
apply when reassembling the Lo tite
243 and on the s rews and tighten to a
torque of 12 Nm ..
• Reassemble the assembly following the
reverse pro ess and lightly greasing the
rear wheel axle.
WARNING
Using a aliper, he k the size of the internal spa er referen e 5931 on the rear wheel
and repla e it if ne essary.
Minimum toleran e: 118.5mm

14
ST SERIES
CYCLE PARTS
2.3 Swingarm bearings control
• Loosen the nut on the lower part of the
swingarm and remove the link pin.
• Loosen the swingarm [1] axle and take
it out.
Tightening axle link : 40 Nm
Swinga m tightening: 50 Nm
• Take out the swingarm and remove
the two internal spa ers [2] .
• Che k the needle ages on ea h side
of the arm. In ase of orrosion,
repla e them with new referen es
C151, otherwise grease them before
reassembly
• Reassemble the assembly following the
reverse pro ess and lightly greasing the
swingarm and onne ting rod pins.
9
2
1

15
ST SERIES
CYCLE PARTS
2.4 Control of suspension lin s
• Loosen, respe tively, the lower
suspension axle [1] and the link axle nut
[2].
• Remove the two axes and take out the
delta links.
• Che k the needle ages, in the event of
orrosion or signs of wear, repla e
them with new ones. Grease during
reassembly.
Shock abso be axle tightening : 40
Nm
Tightening Axle link : 40 Nm
• Remove the two axes of rear link [3].
Link axles : 40 Nm
• Remove the spa ers from the links
and he k the fri tion rings [4]. If
there is any wear, repla e them with
new ones.
• Reassemble the assembly by following
the reverse pro ess and taking are to
grease all the axes and bearings.
1
2
1
3
4

16
ST SERIES
OPERATIONS REQUIRING REMOVAL OR NOT OF THE ENGINE
Ope ation equi ing engine
emoval
Ope ation not equi ing
engine emoval
C ankshaft (including
connecting od kit)
•
Complete
gea box
•
C ankshaft bea ing
•
Gea box bea ing
•
Piston
•
Cylind
e
•
Head cylinde
•
Ignition
•
Kick sta te
•
clutch
•
Wate pump
•
Gea box selection
•

17
ST SERIES
ENGINE REMOVAL / ASSEMBLY
ENGINE REMOVAL
• Drain the oolant (see user manual)Déposer la boite à air.
• Remove the air box and the tank.
• Dis onne t the entire ele tri al harness onne ted to the engine (alternator, spark plug ap, CDI)
• Remove the exhaust.
• Remove the oil.
• Remove the arburetor.
• Remove the se ondary transmission hain (qui k oupler).
• Remove the slave ylinder
• Remove the water hoses onne ted to the engine.
• Loosen all the engine s rews.
• Remove the swingarm.
• Remove the ylinder head mounting bra ket.
• Remove the motor axles.
• Take out the engine.
REASSEMBLY OF THE ENGINE IN THE FRAME
For reassembly pro eed in the reverse dire tion to disassembly respe ting the tightening torques of the s rews
and nuts
Tightening to que:
Engine axles : 40Nm
Swinga m nut : 50 Nm
Slave cylinde sc ews: 10 Nm
Head cylinde holde sc ews : 23Nm
Exhaust sc ews: 10Nm
WARNING
To remove the engine, you must remove the pivot axle of the swing arm, whi h allows
you to deta h the rear wheel / swing arm assembly. To prevent the motor y le from
overturning, make sure that it is held by the hassis.
WARNING
When the lut h re eiver is removed, the piston is no longer held. Hold the piston down
with a plasti ollar.

1
ST SERIES
DISASSEMBLY OF THE ENGINE
❱❘ Oil drain
• Remove the drain s rew [1] and the plug
[2], allow the oil to drain by tilting the
motor y le .
❱❘ Removal of front spro ket
and sele tor
• Remove the pin [3]
• Remove the front spro ket [4].
• Remove the s rew [5] and take out the
sele tor.
• Remove the lut h push rod.
1
2
3
4
5
1