SHERCO ST Series Instruction manual

MANUAL DE TALLER / MANUEL D’ATELIER / WORKSHOP MANUAL
M
ANUAL DE TALLER / MANUEL D’ATELIER / W
O
RKSH
O
P MANUAL
800-607-8742

124
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124
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TABLE OF CONTENTS
Prologue ______________________________________________________________________3
List of special tools and equipment........................................................................................4
Tightening torques................................................................................................................. 4
Technical features of the engine.............................................................................................5
Technical features of the frame ..............................................................................................6
Cycle parts section ____________________________________________________________7
Changing wheel bearing ........................................................................................................8
Changing front flexible brake hose. Formula, AJP, Braktec................................................9-10
Front brake maintenance. Formula, AJP, Braktec............................................................11-12
Changing front brake disc.................................................................................................... 13
Steering shaft ......................................................................................................................14
Front suspension................................................................................................................. 15
Changing right suspension bar seal ................................................................................16-17
Changing left suspension bar seal .......................................................................18-19-20-21
Carburettor and reed block....................................................................................... 23-24-25
Clutch pump ....................................................................................................................... 26
Radiator ..............................................................................................................................27
Footrests .............................................................................................................................28
Engine protector..................................................................................................................28
Electrical system.................................................................................................................. 29
Changing headlight LEDs .................................................................................................... 30
Tilting axle ...........................................................................................................................31
Rear suspension.................................................................................................................. 32
Rear brake and secondary transmission maintenance ....................................................33-34
Fuel tank ............................................................................................................................. 35
Exhaust pipe assembly maintenance ..............................................................................36-37
Changing muffler fibres........................................................................................................ 38
Engine parts section __________________________________________________________39
Changing the piston ................................................................................. 40-41-42-43-44-45
Verifying piston and cylinder.................................................................................................46
Ignition ...........................................................................................................................47-48
Clutch discs ........................................................................................................................ 49
Start routine.............................................................................................................. 50-51-52
Gear selector..................................................................................................................53-54
Gears and crankshaft .....................................................................................55-56-57-58-59
Water pump ........................................................................................................................60

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PROLOGUE
All the information contained in this manual has been prepared to provide the most information on possible operations on a Sherco
motorcycle within ST trial line. Bearing in mind that many of the specific operations must be performed in a specialised workshop,
this manual is intended as a very useful guide for operators carrying out these tasks, bearing in mind that, in many cases, they are
exceptional, infrequent tasks, this manual will help you to follow an order of assembly and action upon elements to be verified or
substituted. It also seeks to help any operator or technician to become familiarised with the processes and resolve any doubts.
Sherco is committed to providing its technical centres with maximum information in order to perform maintenance and repair work
on its motorcycles with maximum guarantees. It must be taken into account that all the processes described in this manual, as well
as the measurements, refer to standard procedures, always using original Sherco parts.
Neatness and the correct execution of all verification or changing of parts, maintaining rigour in developing all processes, and en-
suring perfect dynamic operation is Sherco's objective, in order for ST owners to be able to enjoy their qualities.
Sherco's commitment to continual research and development ensures that its motorcycles are constantly evolving. On account of
the informative nature of this manual, Sherco Motorcycles reserves the right to make changes without prior notice.

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❱❘
❱❘
LIST OF SPECIAL TOOLS AND EQUIPMENT
Clutch block R-037
Magnetic flywheel extractor R-075
Bearing HK 808 (water pump) 2080
Engine starter shaft seal 2074
Pump shaft cap R232
Desmodromic bearing R465
Filter cover 4179
Cylinder head screws 10Nm
Cylinder nuts 22Nm
Magnetic flywheel cover screws 0.7Nm
Stator screws 0.7Nm
Magnetic flywheel nut 100Nm
Clutch spring screws 0,7Nm
Clutch nut 40Nm (with Loctite 243 sealer)
Intake nozzle screws 0.7Nm
Engine closure screws (carter) 15Nm
Primary cog nut 60Nm
M-5 Screws 0.6Nm
M-6 Screws 12Nm
M-8 Screws 24Nm
M-10 Screws 40Nm
Rear wheel axle nut 100Nm
Front wheel axle 100Nm
Lower steering nut 20Nm
Upper steering nut 20Nm
Tilting axle 50Nm
SPECIAL TOOLS
ENGINE TIGHTENING TORQUES

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❱❘
TECHNICAL FEATURES OF THE ENGINE
80 ST 125 ST 250 ST 290 ST 305 ST
Engine 2 stroke by Sherco
Capacity 74.60 cc 123.70 cc 249.70 cc 272 cc 294 cc
Diameter x Stroke 44.50 x 50.70 54 x 54 72.80 x 60 76 x 60 79 x 60
Nikasil cylinder piston tolerance 0.02 mm 0.04 mm 0.03 mm 0.035 mm 0.05 mm
Piston Alclad aluminium
Electronic ignition Leonelli Digital Hidria Digital Hidria Digital Hidria Digital Hidria Digital
Spark plug W16EPR-U3021 W16EPR-U3021 W16EPR-U3021 W16EPR-U3021 W16EPR-U3021
Electrode distance 0.7 0.7 0.7 0.7 0.7
Lubrication 2 % oil mixture
Fuel 98 oct. unleaded gasoline
Carburettor Dell’Orto PHBL26BS Keihin Ø 28 mm Dell’Orto PHBL26BS Keihin Ø 28 mm Keihin Ø 28 mm
Carburettor adjustment Main jet 105 Main jet 122 Main jet 122 Main jet 125 Main jet 128
Edle jet 45 Edle jet 50 Edle jet 33 Edle jet 42 Edle jet 42
Needle position P3 P5 P2 +0.5 P4+0.5 P4+0.5
Refrigeration Forced-circulation liquid cooled
Starter Cog system with retracting pedal
Exhaust Stainless steel tube with aluminium muffler
Primary transmission 5 sp. sequential selection with neutral selector.
1st 13:33
2nd 15:35
3rd 18:33
4th 24:26
5th 31:20
Final transmission 9:54 9:48 10:42 10:42 10:42
Clutch Wet hydraulic multi-plate
Oil capacity 450c.c 10W50W Minerva
ENGINE

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TECHNICAL FEATURES OF THE FRAME
80 ST 125 ST 250 ST 290 ST 305 ST
Frame Tubular Chrome-moly
Gasoline tank Ergal aluminium with integrated fuel pump
Tank capacity 2.6 L 2.6 L 2.6 L 2.6 L 2.6 L
Front brake Hydraulic, Ø 185 mm disc
Rear brake Hydraulic, Ø 145 mm disc
Brake fluid DOT 4 Minerva
Front suspension 39 mm. telescopic Tech fork 165 mm range
Oil capacity Right bar 280 c.c. SAE 5 / Left bar 110 mm from the end of the compressed bar SAE 5
Rear suspension Progressive system of link rods. Alclad aluminium swivel
Damper travel 175 mm 175 mm 175 mm 175 mm 175 mm
Damper Olle R16V R16V R16V R16V
Front wheel 21” aluminium hub
Michelin front tyre c/c 2.75x21 (2.50x19) 2.75x21 2.75x21 2.75x21 2.75x21
Inflated pressure 0.4 bar 0.4 bar 0.4 bar 0.4 bar 0.4 bar
Rear wheel 18” Morad aluminium hub
Michelin rear tyre s/c 4.00x18 (3.50x17) 4.00x18 4.00x18 4.00x18 4.00x18
Inflated pressure 0.3 bar 0.3 bar 0.3 bar 0.3 bar 0.3 bar
Weight 67 kg 67 kg 68 kg 68 kg 68 kg
Distance between axles 1322 mm 1322 mm 1322 mm 1322 mm 1322 mm
Minimum clearance from ground 310 mm 310 mm 310 mm 310 mm 310 mm
Seat height 645 mm 645 mm 645 mm 645 mm 645 mm
CHASSIS

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CYCLE PART

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CHANGING WHEEL BEARING
- Loosen axle block nut
- Loosen and remove front axle
- Release the wheel The bearings are
mounted on either side of the bushing.
When changing the bearings, note the
separator sleeve mounted between
them.
- Loosen the rear axle and remove the
axle towards the left.
- As with the front wheel, the bearings go
on either side of the bushing with the
inner separator between them. Bear in
mind the separator that goes between
the bearing and the swivel when
reassembling.
- When dismantling, it is convenient to
heat the surface where the bearing
is lodged and remove it using a ø20
pushing tube. Decant the pusher
slightly on the front wheel in order to
remove the bearing.

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- Dismantle the front fork bridge and
remove the flexible brake hose from
the bridge, as well as the upper flange.
Dismantle the flexible brake hose.
- Once the flexible brake hose has been
changed, fill up the tank with DOT4
Minerva brake fluid.
- Loosen the grasper bleeder and purge
the flexible brake hose by pressing
successively until the brake lever limit is
reached. Repeat this operation until the
lever at pressure feels to have reached
maximum hardness.
- Fluid level must be checked once
bleeding has been completed.
- Dismantle the flexible brake hose.
❱❘
FORMULA
❱❘
AJP
CHANGING FRONT FLEXIBLE BRAKE HOSE

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BRAKTEC
CHANGING FRONT FLEXIBLE BRAKE HOSE
- Once the flexible brake hose has been
changed, fill up the tank with DOT4
Minerva brake fluid.
- Loosen the grasper bleeder and purge
the flexible brake hose by pressing
successively until the brake lever limit is
reached. Repeat this operation until the
lever at pressure feels to have reached
maximum hardness.
- Fluid level must be checked once
bleeding has been completed. Fluid
level must reach half way up the viewer.
- Dismantle the flexible brake hose.
- Once the flexible brake hose has been
changed, fill tank half way with new
brake fluid.
- Loosen the grasper bleeder and purge
the flexible brake hose by pressing
successively until the brake lever limit is
reached. Repeat this operation until the
lever at pressure feels to have reached
maximum hardness.
- Fluid level must be checked once
bleeding has been completed.

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FRONT BRAKE MAINTENANCE
- Remove the safety clip.
- Loosen the brake pad fixation screw.
- Loosen the grasper securing screws.
- Clean the assembly with Minerva Brake
Cleaner.
- Remove the brake pads.
- Measure the depth of the sheathing. The
inner groove measurement should be
no less than 1mm.
- Remove the safety clip.
- Loosen the brake pad fastening screw.
- Loosen the grasper securing screws.
- Remove the brake pads.
- Measure the depth of the lining. This
cannot be less than 1mm.
❱❘
FORMULA
❱❘
AJP

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- Remove the safety clip.
- Loosen the brake pad fastening screw.
- Loosen the grasper securing screws.
- Remove the brake pads.
- Measure the depth of the lining. This
cannot be less than 1mm.
❱❘
BRAKTEC
❱❘
PARTS BREAKDOWN
FRONT BRAKE MAINTENANCE
FORMULA
BRAKTEC

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- Loosen axle block nut
- Loosen and remove front axle
- Loosen the nuts that secure the discs,
taking care not to damage the edges of
the discs which may present burrs from
the wear and tear.
- When assembling the discs, apply
Loctite 243 to the screws in order to
ensure greater adherence.
- Tighten the screws to 12NM using a
dynamometric spanner.
CHANGING FRONT FLEXIBLE BRAKE HOSE
❱❘
PARTS BREAKDOWN

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STEERING SHAFT
- Dismantle handlebar securing flanges.
- Turn the lower locknut clockwise 1/4 of a
turn and then loosen the upper nut.
- Loosen the platen screws and release
the suspension bars.
- Remove the lower nut.
- From the underside, release the steering
shaft from its position in the chassis.
- Clean all parts.
- Check and replace the bearing if
necessary. Before reassembling,
lubricate with plenty of Minerva grease.
- Upon reassembling, once the upper
platen is mounted, first tighten the
upper nut to 20NM and then lock it
with the lower nut until the assembly is
released and is able to turn freely and
precisely. Use the marks to adjust the
final handlebar position.
❱❘
PARTS BREAKDOWN

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FRONT SUSPENSION
- Loosen the front bridge that joins
the two suspension bars and the
mudguard support.
- Remove the front wheel.
- Remove the front mudguard.
- Loosen the locking screws from the
upper and lower platens.
- Release the front brake grasper.
- Cut the securing flange of the headlight
bracket.
- Slide the bar along the underside.

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CHANGING RIGHT SUSPENSION BAR SEAL
- Upon fixing the bar on the bench, add a
protective element to avoid erosion.
- Loosen the upper plug.
- Loosen the locknut.
- Hold the axle plug.
- Insert a tube in the axle drill and loosen
the cartridge plug.
- Remove the cartridge locking screw and
the oil retaining washer.
- Remove the cartridge from the bar.
- Turn the bar and remove the end-of-run
cone.
- Push the compression group inward and
remove the circlip from its seat.
- Place the hydraulic group back in the
cartridge.
- Insert the end-of-run cone.

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CHANGING RIGHT SUSPENSION BAR SEAL
- Lever the edge of the dust cover and
remove it from the bottle.
- Remove the circlip from its seat.
- Dismantle the bottle seal and cap.
- Apply grease to the bottle mouth to
make assembly easier.
❱❘
PARTS BREAKDOWN

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CHANGING LEFT SUSPENSION BAR SEAL
- Before fixing the bar on the screw,
use protective material to prevent
scratching.
- Loosen the plug and remove it
completely.
- Remove both tapered separators.
- Remove the washer and the spring
slowly to avoid splashing oil.
- Place all the elements on a clean surface
and empty the oil into a container.
- Secure the protected bottle and loosen
the pumping die to be able to remove
the oil-retaining washer and screw.

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CHANGING LEFT SUSPENSION BAR SEAL
- Fully remove the pumping group.
- Invert the bar and remove the end-of-run
cone.
- Lever the edge of the dust cover and
remove it from its seat on the bar.
- Remove the circlip from its seat.
- Secure the protected bar with the
screw and slide the bottle until it is fully
removed.
- Slide all parts indicated from the tube
and replace part A.
- Grease the sleeve and seal seat before
starting reassembly.
- Place the sleeve on its seat using the
appropriate tools.
- Insert the washer, paying special
attention to place its lip facing upward.
- Grease the tube with special sealing
grease.

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CHANGING LEFT SUSPENSION BAR SEAL
- Slide the dust cover down the bar
turning slightly to find its correct
position on the bottle.
- Insert the pumping group with the end-
of-run cone ready mounted.
- While holding the tube at the end of its
run with the help of the spring within
the bar, fully tighten the pumping
screw.
- Tighten the plug to 23.5--25.5 NM using
a dynamometric spanner.
- Position the bar vertically and pour in
some of the new oil.
- Pump a few times, pushing the tube
to the end of its run. Fill with oil up to
110mm from the brim.
- Insert the spring.
- Insert the separating washer.
- Insert the spacer.