SHERCO ST 125 Workshop Manual Download Page 6

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ST SERIES

TECHNICAL SHEET

ENGINE

125

250

300

Types

Mono-cylinder 2 Stroke liquid cooled

Displacement

123,70cc

249,70cc

294 CC

Bore / Stroke

54X54 mm

72,8X60 mm

79C60 mm

Fuel

Lead-free with an octane rating of at least 98 mixed with 2-stroke oil (2%)

Cooling

Liquid with forced circulation

Ignition

Hidria Digital

Spark plug

W16EPR-U3021

Distance between
spark plug electrodes

0.7 mm

Piston

Aluminum foundry with graphic processing

Engine oil

580 ml ATF type

Primary transmission

20X76

24X70

Gear box

5 gears

1st

13 : 33

2nd

15 : 35

3rd

18 : 33

4th

24 : 26

5th

31 : 20

Final transmission

9 X 42

9 X 44

Clutch

Diaphragm system, hydraulic control

Starter

Retractable gear and kick system

Summary of Contents for ST 125

Page 1: ...ST SERIES...

Page 2: ...1...

Page 3: ...gnition 23 Intake pipe and reed box 23 Removal stator 24 Separate the crankcase 24 Removing the gear box 25 Removing the connecting rod assembly 26 ENGINE ELEMENT CONTROL 27 Balance weight external di...

Page 4: ...ied mechanics working in a properly equipped workshop The execution of the various operations requires solid mechanical knowledge and SHERCO tools specific FOR the 125 250 300 ST engines This workshop...

Page 5: ...eferences Designation R172 Clutch lock 2080 Water pump bearing tool 2074 Starter shaft seal tool R232 Water pump tip tool R465 Barrel bearing tool 2073 Spring block selection finger 1821 Engine suppor...

Page 6: ...il 2 Cooling Liquid with forced circulation Ignition Hidria Digital Spark plug W16EPR U3021 Distance between spark plug electrodes 0 7 mm Piston Aluminum foundry with graphic processing Engine oil 580...

Page 7: ...ing Rear shock Hydraulic rear shock Reiger 2way FACTORY Hydraulic rear shock R16V RACING Aluminium swing arm Forward reverse stroke FACTORY 165 175mm RACING 165 175mm Front brake Disc 185mm Rear brake...

Page 8: ...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...

Page 9: ...clicks Limit adjustment Starting from the fully closed position open 2 5 turns Hydraulic compression Starting from the fully closed position open 1 75 turns Left arm oil level 130 mm Right arm oil lev...

Page 10: ...hen replace them with new ones reference 0175 1 2 Front disc replacement When replacing the front brake disc apply when reassembling the Loctite 243 and on the screws and tighten to a torque of 12Nm P...

Page 11: ...per triple clamp then remove it Triple clamp screw 24 Nm Loosen the steering column lock nut 4 and its dust cover then separate the complete Fork of the frame Replace the bearings located in the upper...

Page 12: ...he fork tube so that you have access to the nut 2 Hold the plug 1 and loosen the nut 2 using a 14mm wrench Remove the plug from the diving tube Hold the rod inside the axle 3 then empty the oil in a c...

Page 13: ...imum stop Measure the oil level from the top of the tube top up until you reach the desired value Oil level 75mm Unscrew the diving rod nut as much as possible and install the plug Tighten the plug 4...

Page 14: ...e arm with 250cc of new oil Pump the tube several times then place it in the maximum compression position Measure the volume from the top of the tube and top up with oil until you reach the desired le...

Page 15: ...gun Extract the bearings using a 20 flush Replace the bearings with new ones reference 0175 2 2 Disc replacement When replacing the rear brake disc apply when reassembling the Loctite 243 and on the...

Page 16: ...htening axle link 40 Nm Swingarm tightening 50 Nm Take out the swingarm and remove the two internal spacers 2 Check the needle cages on each side of the arm In case of corrosion replace them with new...

Page 17: ...sion or signs of wear replace them with new ones Grease during reassembly Shock absorber axle tightening 40 Nm Tightening Axle link 40 Nm Remove the two axes of rear link 3 Link axles 40 Nm Remove the...

Page 18: ...GINE Operation requiring engine removal Operation not requiring engine removal Crankshaft including connecting rod kit Complete gearbox Crankshaft bearing Gearbox bearing Piston Cylinder Head cylinder...

Page 19: ...mounting bracket Remove the motor axles Take out the engine REASSEMBLY OF THE ENGINE IN THE FRAME For reassembly proceed in the reverse direction to disassembly respecting the tightening torques of th...

Page 20: ...ve the drain screw 1 and the plug 2 allow the oil to drain by tilting the motorcycle Removal of front sprocket and selector Remove the pin 3 Remove the front sprocket 4 Remove the screw 5 and take out...

Page 21: ...DISASSEMBLY OF THE ENGINE Removing the cylinder head cylinder and piston Remove the M6 screws 1 and remove the cylinder head and the O rings Remove the 4 cylinder nuts 2 Remove the cylinder Hide the...

Page 22: ...ps Remove the piston pin Remove the piston and take out the needle bearing from the big end Remove the base gasket Removing the clutch cover Remove the screws and the water pump cover Remove the seal...

Page 23: ...d the levers 5 Take the discs out of the boss clutch and place the tool R172 6 then remove the clutch nut 7 and the primary gear nut 8 Kick axle removal Remove the clip 1 then remove the idler gear 2...

Page 24: ...scorpion of the selection axle to the left and remove the axle from its housing Loosen the M6 screw 1 then take out the selection finger Loosen the M6 screw 2 then remove the selection star 1 2 WARNIN...

Page 25: ...NE Ignition Removal Remove the previously loosened nut 1 Fit the extractor 2 reference R075 and tear off the magnetic flywheel 3 Intake pipe and reed box Remove the 4 screws M5 4 Remove the intake pip...

Page 26: ...ree M6 screws 1 for fixing the stator then the two M5 screws 2 for fixing the pick up sensor and take out the assembly Separate the crankcase Tilt the engine so that the ignition side is facing you Re...

Page 27: ...ve all of their bearings the primary secondary shaft barrel and right fork simultaneously WARNING Avoid as much as possible the insertion of a screwdriver or any other tool between the crankcases to s...

Page 28: ...rom its bearing possibly by tapping lightly with a plastic mallet at the end of the crankshaft Clean all the parts and check if they are worn replace them if necessary WARNING When the engine is compl...

Page 29: ...dial clearance Standard 0 015 mm 0 025 mm Limit 0 06 mm If the radial clearance is greater than the tolerated limit the crankshaft must be replaced Connecting rod end side clearance Measure the side p...

Page 30: ...der and place it with the piston approximately 10 mm from the upper edge of the cylinder With a shim we measure the clearance End gap Standard 0 35 0 45mm Limit 0 65mm Piston pin control Piston pin di...

Page 31: ...oth directions to identify a possible ovality 125cc 250cc 300cc A B A B A B Piston 53 96 53 97 72 75 72 76 78 95 78 96 Cylinder 53 975 53 985 72 79 72 802 79 79 012 Free play 0 015 0 015 0 04 0 042 0...

Page 32: ...guides Clutch hub 9 Check the wear of the smooth disc seats Disc control On diaphragm clutches the thickness of the discs is checked on the complete assembly and not individually Minimum thickness 9...

Page 33: ...R Right Insert the forks 2 on the gears and mount the gearbox fork assembly in the crankcase Slightly pull out the secondary shaft and hold the 4th gear up so that the fork is in place in the barrel...

Page 34: ...ase the oil seals of the left crankcase and put it in place Put the screws and tighten to 10 Nm Then tap lightly with a plastic mallet on the crankshaft and check that the shafts turn without any hard...

Page 35: ...lock the screw and assemble the selection star on the drum Tighten the M6 screw to 10 Nm Grease the already assembled selection shaft and thread it into the needle bearings without forgetting the sett...

Page 36: ...4 and tighten the screw 5 M6 to 10Nm Primary transmission and clutch Place the half moon key in its housing Apply loctite 243 to the thread Thread the gear the washer and the nut on the crankshaft tai...

Page 37: ...the primary shaft Fit tool R172 to hold the clutch and tighten the clutch nut 5 to 40 Nm as well as that of the primary gear 6 to 60Nm Reassemble respectively 1 The push rod of the clutch rod with th...

Page 38: ...ter pump assembly is in place Rotate the rotor so that the water pump gear can mesh with the primary transmission gear Put the THEP M6 screws and tighten to 10 Nm Water pump cover Place the seal on th...

Page 39: ...distance between the flat of the piston at top dead center and the plane of the cylinder head To do this use a strand of tin that you will place on the piston Depending on the value obtained adjust wi...

Page 40: ...Put the complete reed box in the intake conduct Put on a new intake pipe gasket Mount the intake pipe with the 4 M5 screws tighten them to 6Nm Front sprocket Fit the retaining circlip on the engine si...

Page 41: ...flywheel nut 100 N m Clutch spring screws 0 7 N m Clutch nut 40 N m Loctite 243 Screw intake pipe 0 7 N m Crankcase screw 15 N m Primary gear nut 60 N m Screws M 5 0 6 N m Screws M 6 12 N m Screws M 8...

Page 42: ...40 ST SERIES ELECTRICAL PART Electrical components Position Designation 1 Ventilator 2 T Sensor 3 Ignition coil 4 Regulator 5 Ignition 6 CDI 1 2 3 4 5 6...

Page 43: ...125cc Wire Yellow Yellow 0 7 1 5 Hall sensor control Disconnect the CDI connector Connect a multimeter to the hall sensor terminals 10 11 Measure with the multimeter the resistance between the white...

Page 44: ...he resistance of the primary coil as follows Primary coil measure the resistance between the ground and the coil output to the CDI Secondary coil measure the resistance between the ground and the outp...

Page 45: ...ol its temperature Heat the liquid slowly and check the resistance of the sensor using a connected multimeter as in the diagram according to the temperature of the liquid refer to the table below Vent...

Page 46: ...44 ST SERIES CABLE SCHEMATICS Homologated light harness...

Page 47: ...45 ST SERIES CABLE SCHEMATICS Homologated light harness...

Page 48: ...46 ST SERIES CABLE SCHEMATICS Racing light harness...

Page 49: ...47 ST SERIES CABLE SCHEMATICS Principal harness...

Page 50: ...48 ST SERIES CABLE SCHEMATICS Principal harness...

Page 51: ......

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SHERCO ST 125, Workshop Manual

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