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Manual Yamaha YZ125N1

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  • Yamaha YZ125N1 - page 1

    5MV -28199-10 LIT -1 1626-14-36 PAN YZ125N1 YZ1 2 5N1 OWNER’S SER VICE MANUAL 5MV-10 00.6.13 0:53 PM y[W 1 (2,1) ...

  • Yamaha YZ125N1 - page 2

    5MV-10 00.6.13 0:53 PM y[W 2 (1,1) ...

  • Yamaha YZ125N1 - page 3

    YZ125N1 OWNER’S SERVICE MANUAL © 2000 by Y amaha Motor Corporation, U.S.A. 1st Edition, June 2000 All rights reserved. Any reprinting or unauthorized use without the written permission of Y amaha Motor Corporation U.S.A. is expressly prohibited. Printed in Japan P/N. LIT -1 1626-14-36 EC010000 5MV-9-10-0 6/13/00 3:11 PM Page 1 ...

  • Yamaha YZ125N1 - page 4

    EC020000 INTRODUCTION Congratulations on your purchase of a Y amaha YZ series. This model is the culmination of Y amaha’s vast experience in the production of pacesetting racing machines. It represents the highest grade of craftsmanship and reliability that have made Y amaha a leader . This manual explains operation, inspection, ba- sic maintenan ...

  • Yamaha YZ125N1 - page 5

    Yamaha Motor Corporation, U.S.A. hereby warrants to the origi- nal retail purchaser that the following components equipped on new Yamaha YZ or WR motorcycles purchased from an autho- rized Yamaha motorcycle dealer in the continental United States will be free from defects in materiel and workmanship for the period of time stated herein, subject to ...

  • Yamaha YZ125N1 - page 6

    EC040001 IMPORT ANT NOTICE THIS MACHINE IS DESIGNED STRICTL Y FOR COMPETITION USE, ONL Y ON A CLOSED COURSE. It is illegal for this machine to be op- erated on any public street, road, or highway . Off-road use on public lands may also be illegal. Please check local regulations before riding. 1. THIS MACHINE IS TO BE OPERA TED BY AN EXPERIENCED RID ...

  • Yamaha YZ125N1 - page 7

    5. GASOLINE IS HIGHL Y FLAMMABLE. Always turn off the engine while refuel- ing. T ake care to not spill any gasoline on the engine or exhaust system. Never refuel in the vicinity of an open flame, or while smoking. 6. GASOLINE CAN CAUSE INJUR Y . If you should swallow some gasoline, inhale excess gasoline vapors, or allow any gasoline to get into y ...

  • Yamaha YZ125N1 - page 8

    EC050000 TO THE NEW OWNER This manual will provide you with a good basic understanding of features, operation, and basic maintenance and inspection items of this ma- chine. Please read this manual carefully and completely before operating your new machine. If you have any questions regarding the opera- tion or maintenance of your machine, please co ...

  • Yamaha YZ125N1 - page 9

    EC080000 HOW T O USE THIS MANUAL EC081000 P ARTICULARL Y IMPORT ANT IN FORMA TION Q The Safety Alert Symbol means A TTENTION! BECOME ALERT! YOUR SAFETY IS IN- VOL VED! w Failure to follow W ARNING instructions could re- sult in severe injury or death to the machine op- erator , a bystander , or a person inspecting or re- pairing the machine. c C A ...

  • Yamaha YZ125N1 - page 10

    EC083000 MANUAL FORMA T All of the procedures in this manual are organized in a sequential, step-by-step format. The informa- tion has been complied to provide the mechanic with an easy to read, handy reference that contains comprehensive explanations of all disassembly , repair , assembly , and inspection operations. In this revised format, the co ...

  • Yamaha YZ125N1 - page 11

    EC085002 ILLUSTRA TED SYMBOLS (Refer to the illustration) Illustrated symbols 1 to 7 are designed as thumb tabs to indicate the chapter ’s number and content. 1 General information 2 Specifications 3 Regular inspection and adjustments 4 Engine 5 Chassis 6 Electrical 7 Tuning Illustrated symbols 8 to r are used to identify the specifications appea ...

  • Yamaha YZ125N1 - page 12

    ENGINE CHASSIS ELECTRICAL TUNING REGULAR INSPECTION AND ADJUSTMENTS SPECIFICA TIONS EC090000 INDEX GENERAL INFORMA TION GEN INFO 1 2 3 4 5 6 7 SPEC INSP ADJ ENG CHAS ELEC TUN 5MV-9-10-0 6/13/00 3:11 PM Page 11 ...

  • Yamaha YZ125N1 - page 13

    EC0A0000 CONTENTS CHAPTER 1 GENERAL INFORMA TION DESCRIPTION ............................................1-1 MACHINE IDENTIFICA TION ......................1-2 IMPORT ANT INFORMA TION .....................1-3 CHECKING OF CONNECTION ..................1-6 SPECIAL TOOLS ........................................1-7 CONTROL FUNCTIONS ..................... ...

  • Yamaha YZ125N1 - page 14

    CHAPTER 4 ENGINE SEA T , FUEL T ANK AND SIDE COVERS .....................................................4-1 EXHAUST PIPE AND SILENCER ..............4-3 RADIA TOR ..................................................4-4 CARBURETOR AND REED V AL VE ...........4-7 CYLINDER HEAD , CYLINDER AND PISTON .....................................................4 ...

  • Yamaha YZ125N1 - page 15

    CHAPTER 6 ELECTRICAL ELECTRICAL COMPONENTS AND WIRING DIAGRAM .....................................6-1 IGNITION SYSTEM .....................................6-2 CHAPTER 7 TUNING ENGINE .......................................................7-1 CHASSIS ...................................................7-13 5MV-9-10-0 6/13/00 3:11 PM Page 14 ...

  • Yamaha YZ125N1 - page 16

    1-1 GEN INFO DESCRIPTION EC100000 GENERAL INFORMA TION EC110000 DESCRIPTION 1 Clutch lever 2 ”ENGINE STOP” button 3 Front brake lever 4 Throttle grip 5 Radiator cap 6 Fuel tank cap 7 Kick starter 8 Fuel tank 9 Radiator 0 Coolant drain bolt q Check bolt (Transmission oil level) w Rear brake pedal e Valve joint r Fuel cock t Air cleaner y Drive c ...

  • Yamaha YZ125N1 - page 17

    1-2 GEN INFO MA CHINE IDENTIFICA TION EC120001 MA CHINE IDENTIFICA TION There are two significant reasons for knowing the serial number of your machine: 1. When ordering parts, you can give the num- ber to your Y amaha dealer for positive iden- tification of the model you own. 2. If your machine is stolen, the authorities will need the number to se ...

  • Yamaha YZ125N1 - page 18

    1-3 GEN INFO IMPOR T ANT INFORMA TION EC130000 IMPOR T ANT INFORMA TION EC131010 PREP ARA TION FOR REMO V AL AND DISASSEMBL Y 1. Remove all dirt, mud, dust, and foreign ma- terial before removal and disassembly . When washing the machine with high pres- sured water , cover the parts as follows. 9 Silencer end 9 Air filter intake slit 9 Crankcase co ...

  • Yamaha YZ125N1 - page 19

    1-4 GEN INFO IMPOR T ANT INFORMA TION EC133000 GASKETS, OIL SEALS AND O-RINGS 1. All gaskets, oil seals, and O-rings should be replaced when an engine is overhauled. All gasket surfaces, oil seal lips, and O-rings must be cleaned. 2. Properly oil all mating parts and bearings during reassembly . Apply grease to the oil seal lips. EC134000 LOCK W AS ...

  • Yamaha YZ125N1 - page 20

    1-5 GEN INFO IMPOR T ANT INFORMA TION EC136000 CIRCLIPS 1. All circlips should be inspected carefully be- fore reassembly . Always replace piston pin clips after one use. Replace distorted cir- clips. When installing a circlip 1 , make sure that the sharp-edged corner 2 is positioned opposite to the thrust 3 it receives. See the sectional view . 4 ...

  • Yamaha YZ125N1 - page 21

    1-6 GEN INFO CHECKING OF CONNECTION EC1C0001 CHECKING OF CONNECTION Dealing with stains, rust, moisture, etc. on the connector . 1. Disconnect: 9 Connector 2. Dry each terminal with an air blower . 3. Connect and disconnect the connector two or three times. 4. Pull the lead to check that it will not come off. 5. If the terminal comes off, bend up t ...

  • Yamaha YZ125N1 - page 22

    1-7 GEN INFO SPECIAL T OOLS EC140001 SPECIAL T OOLS The proper special tools are necessary for complete and accurate tune-up and assembly . Using the correct special tool will help prevent damage caused by the use of improper tools or improvised tech- niques. The shape and part number used for the special tool differ by country , so two types are p ...

  • Yamaha YZ125N1 - page 23

    1-8 GEN INFO SPECIAL T OOLS P ar t number T ool name / How to use IIIustration YU-24460-01, 90890-01325 Radiator cap tester YU-24460-01 90890-01325 YU-33984, 90890-01352 Adapter YU-33984 90890-01352 These tools are used for checking the cooling system. YU-33975, 90890-01403 Ring nut wrench YU-33975 90890-0140 3 This tool is used when tighten the st ...

  • Yamaha YZ125N1 - page 24

    1-9 GEN INFO CONTR OL FUNCTIONS EC150000 CONTR OL FUNCTIONS EC151000 “ENGINE ST OP” BUTT ON The “ENGINE STOP” button 1 is located on the left handlebar . Continue pushing the “ENGINE STOP” button till the engine comes to a stop. EC152000 CLUTCH LEVER The clutch lever 1 is located on the left handle- bar; it disengages or engages the clu ...

  • Yamaha YZ125N1 - page 25

    1-10 GEN INFO CONTR OL FUNCTIONS EC156000 FRONT BRAKE LEVER The front brake lever 1 is located on the right handlebar . Pull it toward the handlebar to acti- vate the front brake. EC157000 REAR BRAKE PED AL The rear brake pedal 1 is located on the right side of the machine. Press down on the brake pedal to activate the rear brake. EC158001 FUEL COC ...

  • Yamaha YZ125N1 - page 26

    1-11 GEN INFO CONTR OL FUNCTIONS EC15R001 DET A CHABLE SIDEST AND This sidestand 1 is used to support only the machine when standing or transporting it. w 9 Never appl y additional for ce to the side- stand. 9 Remove this sidestand bef ore starting out. EC15F000 V AL VE JOINT This valve joint 1 prevents fuel from flowing out and is installed to the ...

  • Yamaha YZ125N1 - page 27

    1-12 GEN INFO FUEL AND ENGINE MIXING OIL EC160050 FUEL AND ENGINE MIXING OIL Mix oil with the gas at the ratio specified below . Always use fresh, name-brand gasoline, and mix the oil and gas the day of the race. Do not use premix that is more than a few hours old. NO TE: Except for AUS: 1. If knocking or pinging occurs, use a different brand of ga ...

  • Yamaha YZ125N1 - page 28

    1-13 GEN INFO ST ARTING AND BREAK-IN EC190000 ST ARTING AND BREAK-IN c C Before starting the machine, perform the chec ks in the pre-operation check list. w Never start or run the engine in a closed area. The exhaust fumes are poisonous; they can cause loss of consciousness and death in a very shor t time. Always operate the machine in a well-venti ...

  • Yamaha YZ125N1 - page 29

    1-14 GEN INFO ST ARTING AND BREAK-IN EC194001 BREAK-IN PROCEDURES 1. Before starting the engine, fill the fuel tank with a break-in oil-fuel mixture as follows. 2. Perform the pre-operation checks on the machine. 3. Start and warm up the engine. Check the idle speed, and check the operation of the controls and the “ENGINE STOP” button. 4. Opera ...

  • Yamaha YZ125N1 - page 30

    1-15 GEN INFO ST ARTING AND BREAK-IN c C 9 After the break-in or before eac h race, you must c heck the entire machine f or loose fit- tings and fasteners as per “T ORQUE- CHECK POINTS”. Tighten all such fastener s as required. 9 When any of the f ollowing parts have been replaced, they m ust be broken in. CYLINDER AND CRANKSHAFT : About one ho ...

  • Yamaha YZ125N1 - page 31

    1-16 GEN INFO T ORQUE-CHECK POINTS EC1A0012 T ORQUE-CHECK POINTS Frame construction Frame to rear frame Combined seat and tank Fuel tank to frame Engine mounting Frame to engine Steering Steering shaft to Steering shaft to frame handlebar Steering shaft to handle crown Handle crown to handlebar Suspension Front Steering shaft to Front fork to handl ...

  • Yamaha YZ125N1 - page 32

    1-17 GEN INFO CLEANING AND ST ORA GE EC1B0000 CLEANING AND ST ORA GE EC1B1000 CLEANING Frequent cleaning of your machine will enhance its appearance, maintain good overall perfor- mance, and extend the life of many components. 1. Before washing the machine, block off the end of the exhaust pipe to prevent water from entering. A plastic bag secured ...

  • Yamaha YZ125N1 - page 33

    1-18 GEN INFO CLEANING AND ST ORA GE EC1B2001 ST ORA GE If your machine is to be stored for 60 days or more, some preventive measures must be taken to avoid deterioration. After cleaning the ma- chine thoroughly , prepare it for storage as fol- lows: 1. Drain the fuel tank, fuel lines, and the carbu- retor float bowl. 2. Remove the spark plug, pour ...

  • Yamaha YZ125N1 - page 34

    2-1 SPEC GENERAL SPECIFICA TIONS Model name: YZ125LC (EUROPE) YZ125N1 (USA) YZ125(N) (CDN, AUS, NZ, ZA) Model code number: 5MV1 (USA, CDN, ZA) 5MV2 (EUROPE) 5MV4 (AUS, NZ) Dimensions: USA, CDN, ZA EUROPE AUS, NZ Overall length 2,139 mm 2,136 mm 2,139 mm (84.2 in) (84.1 in) (84.2 in) Overall width 827 mm ←← (32.6 in) Overall height 1,318 mm 1,31 ...

  • Yamaha YZ125N1 - page 35

    2-2 SPEC GENERAL SPECIFICA TIONS Carburetor: T ype/Manufacturer TMX χ 38SS/MIKUNI Spark plug: T ype/Manufacturer BR9EG/NGK Gap 0.5~0.6 mm (0.020~0.024 in) Clutch type: Wet, multiple-disc T ransmission: Primary reduction system Gear Primary reduction ratio 64/19 (3.368) Secondary reduction system Chain drive Secondary reduction ratio 48/13 (3.692) ...

  • Yamaha YZ125N1 - page 36

    2-3 SPEC MAINTENANCE SPECIFICA TIONS Item Standard Limit Cylinder head: Combustion chamber capacity 10.2 cm 3 … (0.359 Imp oz, 0.345 US oz) W arp limit … 0.03 mm (0.0012 in) Cylinder: Bore size 54.000~54.014 mm 54.1 mm (2.130 in) (2.1260~2.1265 in) T aper limit … 0.05 mm (0.0020 in) Out of round limit … 0.01 mm (0.0004 in) Piston: Piston si ...

  • Yamaha YZ125N1 - page 37

    2-4 SPEC MAINTENANCE SPECIFICA TIONS Item Standard Limit T ransmission: Main axle deflection limit … 0.01 mm (0.0004 in) Drive axle deflection limit … 0.01 mm (0.0004 in) Shifter: Shifting type Cam drum and guide bar … Guide bar bending limit … 0.05 mm (0.0020 in) Kick starter type: Kick and mesh type … Kick clip friction force P=0.8~1.2 ...

  • Yamaha YZ125N1 - page 38

    2-5 SPEC MAINTENANCE SPECIFICA TIONS Part to be tightened Thread size Q'ty T ightening torque Nm m•kg ft•lb Spark plug M14 × 1.25 1 20 2.0 14 Cylinder head (nut) M 8 × 1.25 5 28 2.8 20 (stud) M 8 × 1.25 5 13 1.3 9.4 Cylinder (nut) M 8 × 1.25 4 30 3.0 22 (stud) M10 × 1.25 4 13 1.3 9.4 Power valve: Cover M 5 × 0.8 4 4 0.4 2.9 Link leve ...

  • Yamaha YZ125N1 - page 39

    2-6 SPEC MAINTENANCE SPECIFICA TIONS Part to be tightened Thread size Q'ty T ightening torque Nm m•kg ft•lb Exhaust pipe M 6 × 1.0 2 12 1.2 8.7 Exhaust pipe stay (front) M 6 × 1.0 1 12 1.2 8.7 Exhaust pipe stay (rear) M 6 × 1.0 1 12 1.2 8.7 Silencer (front) M 6 × 1.0 1 12 1.2 8.7 Silencer (rear) M 6 × 1.0 1 7 0.7 5.1 Fiber (silencer) ...

  • Yamaha YZ125N1 - page 40

    2-7 SPEC MAINTENANCE SPECIFICA TIONS EC212201 CHASSIS Item Standard Limit Steering system: Steering bearing type T aper roller bearing … Front suspension: USA, CDN, ZA EUROPE AUS, NZ Front fork travel 300 mm (1 1.8 in) ← … Fork spring free length 460 mm (18.1 in) ← 455 mm (17.9 in) Spring rate, STD K=4.10 N/mm K =A pprox. … (0.410 kg/mm, ...

  • Yamaha YZ125N1 - page 41

    2-8 SPEC MAINTENANCE SPECIFICA TIONS Item Standard Limit Wheel: Front wheel type Spoke wheel … Rear wheel type Spoke wheel … Front rim size/Material 21 × 1.60/Aluminum … Rear rim size/Material 19 × 1.85/Aluminum … Rim runout limit: Radial … 2.0 mm (0.08 in) Lateral … 2.0 mm (0.08 in) Drive chain: T ype/Manufacturer DID520DMA2 SDH/DAID ...

  • Yamaha YZ125N1 - page 42

    2-9 SPEC MAINTENANCE SPECIFICA TIONS NO TE: 1. First, tighten the ring nut approximately 38 Nm (3.8 m•kg, 27 ft•lb) by using the ring nut wrench, then loosen the ring nut one turn. 2. Retighten the ring nut 7 Nm (0.7 m•kg, 5.1 ft•lb). Part to be tightened Thread size Q'ty T ightening torque Nm m•kg ft•lb Handle crown and outer tube ...

  • Yamaha YZ125N1 - page 43

    2-10 SPEC MAINTENANCE SPECIFICA TIONS Part to be tightened Thread size Q'ty T ightening torque Nm m•kg ft•lb Rear brake master cylinder and frame M 6 × 1.0 2 10 1.0 7.2 Rear brake reservoir tank and frame M 6 × 1.0 1 7 0.7 5.1 Rear brake hose union bolt (caliper) M10 × 1.25 1 30 3.0 22 Rear brake hose union bolt (master cylinder) M10 × ...

  • Yamaha YZ125N1 - page 44

    2-11 SPEC MAINTENANCE SPECIFICA TIONS EC212300 ELECTRICAL Part to be tightened Thread size Q’ty T ightening torque Nm m•kg ft•lb Stator M 6 × 1.0 3 8 0.8 5.8 Rotor M10 × 1.25 1 33 3.3 24 Ignition coil M 6 × 1.0 2 7 0.7 5.1 Item Standard Limit Ignition system: Ignition timing (B.T .D.C.) 32°/3000 r/min … 0.52 mm (0.020 in) … Advancer t ...

  • Yamaha YZ125N1 - page 45

    2-12 SPEC GENERAL T ORQUE SPECIFICA TIONS/ DEFINITION OF UNITS This chart specifies torque for standard faste- ners with standard I.S.O. pitch threads. T orque specifications for special components or assem- blies are included in the applicable sections of this book. T o avoid warpage, tighten multi-faste- ner assemblies in a crisscross fashion, in ...

  • Yamaha YZ125N1 - page 46

    2-13 SPEC CABLE R OUTING DIA GRAM EC240000 CABLE R OUTING DIA GRAM 1 Brake hose 2 Fuel tank breather hose 3 Cable guide 4 Clamp 5 “ENGINE STOP” button lead 6 Throttle cable 7 Air vent hose (right) 8 Air vent hose (left) 9 Transmission oil breather hose 0 Overflow hose q Radiator breather hose w CDI magneto lead e YPVS breather hose A Pass the f ...

  • Yamaha YZ125N1 - page 47

    2-14 SPEC CABLE R OUTING DIA GRAM 1 Brake hose holder 2 Master cylinder 3 Brake hose 4 Hose guide 5 CDI unit band 6 CDI unit 7 High tension cord 8 Ignition coil 9 Cable guide 0 Radiator breather hose q Wireharness w “ENGINE STOP” button lead e CDI magneto lead r Clutch cable t Clamp y CDI unit bracket u Engine bracket i CDI unit damper A Pass t ...

  • Yamaha YZ125N1 - page 48

    2-15 SPEC CABLE R OUTING DIA GRAM A Install the brake hose so that its pipe portion directs as show and lightly touches the projection on the master cylinder. B Pass the “ENGINE STOP” button lead in the middle of the clutch holder. C Pass the clutch cable in front of the throttle cable. D Clamp the “ENGINE STOP” button lead to the handlebar ...

  • Yamaha YZ125N1 - page 49

    3-1 MAINTENANCE INTERV ALS INSP ADJ EC300000 REGULAR INSPECTION AND ADJUSTMENTS EC310051 MAINTENANCE INTERV ALS The following schedule is intended as a general guide to maintenance and lubrication. Bear in mind that such factors as weather , terrain, geographical location, and individual usage will alter the required maintenance and lubrication int ...

  • Yamaha YZ125N1 - page 50

    3-2 MAINTENANCE INTERV ALS INSP ADJ Item Remarks COOLING SYSTEM Check coolant level and leakage ●● Check radiator cap operation ● Replace coolant ● Every two years Inspect hoses ● OUTSIDE NUTS AND BOLTS Refer to “STARTING Retighten ●● AND BREAK-IN” section in the CHAPTER 1. AIR FILTER Clean and lubricate ●● Use foam air-filter ...

  • Yamaha YZ125N1 - page 51

    3-4 PRE-OPERA TION INSPECTION AND MAINTENANCE INSP ADJ EC320000 PRE-OPERA TION INSPECTION AND MAINTENANCE Before riding for break-in operation, practice or a race, make sure the machine is in good operating condition. Before using this machine, check the following points. EC321000 GENERAL INSPECTION AND MAINTENANCE Item Routine Page Coolant Check t ...

  • Yamaha YZ125N1 - page 52

    3-5 ENGINE/COOLANT LEVEL INSPECTION/ COOLANT REPLACEMENT INSP ADJ EC350000 ENGINE EC351011 COOLANT LEVEL INSPECTION w Do not remove the radiator cap 1 1 , drain bolt and hoses when the engine and radia- tor are hot. Scalding hot fluid and steam may be blown out under pressure, which could cause serious injury . When the engine has cooled, place a t ...

  • Yamaha YZ125N1 - page 53

    3-6 COOLANT REPLACEMENT INSP ADJ c C T ake care so that coolant does not splash on painted surfaces. If it splashes, wash it away with water . 1. Place a container under the engine. 2. Remove: 9 Coolant drain bolt 1 3. Remove: 9 Radiator cap Drain the coolant completely . 4. Clean: 9 Cooling system Thoroughly flush the cooling system with clean tap ...

  • Yamaha YZ125N1 - page 54

    3-7 RADIA TOR CAP INSPECTION INSP ADJ c C 9 Do not mix more than one type of ethyl- ene glycol antifreeze containing corro- sion inhibitors for aluminum engine. 9 Do not use water containing impurities or oil. 7. Install: 9 Radiator cap Start the engine and warm it up for a sev- eral minutes. 8. Check: 9 Coolant level Coolant level low → Add cool ...

  • Yamaha YZ125N1 - page 55

    3-8 RADIA TOR CAP OPENING PRESSURE INSPECTION/ COOLING SYSTEM INSPECTION INSP ADJ EC356002 RADIA TOR CAP OPENING PRESSURE INSPECTION 1. Attach: 9 Radiator cap tester 1 and adapter 2 NOTE: Apply water on the radiator cap seal. 3 Radiator cap 2. Apply the specified pressure. 3. Inspect: 9 Pressure Impossible to maintain the specified pres- sure for 1 ...

  • Yamaha YZ125N1 - page 56

    3-9 CLUTCH ADJUSTMENT INSP ADJ NOTE: 9 Do not apply pressure more than specified pressure. 9 Radiator should be filled fully . 4. Inspect: 9 Pressure Impossible to maintain the specified pres- sure for 10 seconds → Repair . 9 Radiator 1 9 Radiator hose joint 2 Coolant leakage → Repair or replace. 9 Radiator hose 3 Swelling → Replace. 2. Adjus ...

  • Yamaha YZ125N1 - page 57

    3-10 THROTTLE CABLE ADJUSTMENT/ THROTTLE LUBRICA TION INSP ADJ EC35A001 THROTTLE CABLE ADJUSTMENT 1. Check: 9 Throttle grip free play a Out of specification → Adjust. 2. Adjust: 9 Throttle grip free play EC35S002 THROTTLE LUBRICA TION 1. Remove: 9 Cap cover 1 9 Throttle cable cap 2 2. Apply: 9 Lithium soap base grease On the throttle cable end a ...

  • Yamaha YZ125N1 - page 58

    3-11 AIR FIL TER CLEANING INSP ADJ 3. Install: 9 Throttle cable cap 9 Cap cover EC35G040 AIR FIL TER CLEANING NOTE: Proper air filter maintenance is the biggest key to preventing premature engine wear and dam- age. c C Never run the engine without the air filter element in place; this would allow dirt and dust to enter the engine and cause rapid we ...

  • Yamaha YZ125N1 - page 59

    3-12 TRANSMISSION OIL LEVEL CHECK INSP ADJ 3. Inspect: 9 Air filter element Damage → Replace. 4. Apply: 9 Foam-air-filter oil or engine mixing oil T o the element. NOTE: Squeeze out the excess oil. Element should be wet but not dripping. 5. Install: 9 Filter guide 1 NOTE: Align the projection a on filter guide with the hole b in air filter elemen ...

  • Yamaha YZ125N1 - page 60

    3-13 TRANSMISSION OIL REPLACEMENT INSP ADJ 3. Check: 9 T ransmission oil level EC35K002 TRANSMISSION OIL REPLACEMENT 1. Start the engine and warm it up for several minutes and wait for five minute. 2. Place the machine on a level place and hold it on upright position by placing the suitable stand under the engine. 3. Place a suitable container unde ...

  • Yamaha YZ125N1 - page 61

    3-14 PILOT AIR SCREW ADJUSTMENT INSP ADJ 4. Remove: 9 Oil drain bolt 1 9 Oil filler cap 2 Drain the transmission oil. 5. Install: 9 Aluminum washer 9 Oil drain bolt 1 6. Fill: 9 T ransmission oil 7. Check: 9 Oil leakage 8. Check: 9 T ransmission oil level 9. Install: 9 Oil filler cap 2 EC35L002 PILOT AIR SCREW ADJUSTMENT 1. Adjust: 9 Pilot air scre ...

  • Yamaha YZ125N1 - page 62

    3-15 IDLE SPEED ADJUSTMENT/MUFFLER INSPECTION/ SILENCER FIBER REPLACEMENT INSP ADJ EC35M010 IDLE SPEED ADJUSTMENT 1. Start the engine and thoroughly warm it up. 2. Adjust: 9 Idle speed EC35P010 MUFFLER INSPECTION 1. Inspect: 9 O-ring 1 Damage → Replace. EC35R041 SILENCER FIBER REPLACEMENT 1. Remove: 9 Seat 9 Side cover (right) 9 Bolt (silencer) 1 ...

  • Yamaha YZ125N1 - page 63

    3-16 SILENCER FIBER REPLACEMENT INSP ADJ 5. Install: 9 Bolt (fiber) 1 9 Silencer 2 9 Bolt [silencer (front)] 3 9 Bolt [silencer (rear)] 4 9 Side cover (right) 9 Seat 10 Nm (1.0 m•kg, 7.2 ft•lb) 12 Nm (1.2 m•kg, 8.7 ft•lb) 7 Nm (0.7 m•kg, 5.1 ft•lb) 2. Remove: 9 Inner pipe 1 3. Replace: 9 Fiber 2 4. Install: 9 Inner pipe NOTE: Fully appl ...

  • Yamaha YZ125N1 - page 64

    3-17 CHASSIS/BRAKE SYSTEM AIR BLEEDING INSP ADJ EC360000 CHASSIS EC361012 BRAKE SYSTEM AIR BLEEDING w Bleed the brake system if: 9 The system has been disassembled. 9 A brake hose has been loosened or removed. 9 The brake fluid is very low . 9 The brake operation is faulty . A dangerous loss of braking performance may occur if the brake system is n ...

  • Yamaha YZ125N1 - page 65

    3-18 FRONT BRAKE ADJUSTMENT INSP ADJ 3. Install: 9 Protector (rear brake) 9 Diaphragm 9 Master cylinder cap EC362040 FRONT BRAKE ADJUSTMENT 1. Check: 9 Brake lever position a 2. Adjust: 9 Brake lever position NOTE: If bleeding is difficult, it may be necessary to let the brake fluid system stabilize for a few hours. Repeat the bleeding procedure wh ...

  • Yamaha YZ125N1 - page 66

    3-19 REAR BRAKE ADJUSTMENT/ FRONT BRAKE P AD INSPECTION AND REPLACEMENT INSP ADJ EC365080 FRONT BRAKE P AD INSPECTION AND REPLACEMENT 1. Inspect: 9 Brake pad thickness a Out of specification → Replace as a set. 2. Replace: 9 Brake pad Brake pad thickness a a : Standard 4.4 mm (0.17 in) <Limit> 1.0 mm (0.04 in) Brake pad replacement steps: 9 ...

  • Yamaha YZ125N1 - page 67

    3-20 FRONT BRAKE P AD INSPECTION AND REPLACEMENT INSP ADJ 9 Loosen the pad pin 2 . 9 Remove the brake hose holder 3 and caliper 4 from the front fork. 9 Remove the pad pin and brake pads 5 . 9 Connect the transparent hose 6 to the bleed screw 7 and place the suitable con- tainer under its end. 9 Loosen the bleed screw and push the caliper piston in ...

  • Yamaha YZ125N1 - page 68

    3-21 REAR BRAKE P AD INSPECTION AND REPLACEMENT INSP ADJ 3. Inspect: 9 Brake fluid level Refer to “BRAKE FLUID LEVEL INSPECTION” section. 4. Check: 9 Brake lever operation A softy or spongy feeling → Bleed brake system. Refer to “BRAKE SYSTEM AIR BLEED- ING” section. EC366060 REAR BRAKE P AD INSPECTION AND REPLACEMENT 1. Inspect: 9 Brake ...

  • Yamaha YZ125N1 - page 69

    3-22 REAR BRAKE P AD INSPECTION AND REPLACEMENT INSP ADJ 9 Remove the pad pin 6 and brake pads 7 . 9 Connect the transparent hose 8 to the bleed screw 9 and place the suitable con- tainer under its end. 9 Loosen the bleed screw and push the caliper piston in. c C Do not reuse the drained brake fluid. 9 T ighten the bleed screw . 9 Install the brake ...

  • Yamaha YZ125N1 - page 70

    3-23 REAR BRAKE P AD INSULA TOR INSPECTION BRAKE FLUID LEVEL INSPECTION INSP ADJ EC36b000 REAR BRAKE P AD INSULA TOR INSPECTION 1. Remove: 9 Brake pad Refer to “ REAR BRAKE P AD INSPEC- TION AND REPLACEMENT” section. 2. Inspect: 9 Rear brake pad insulator 1 Damage → Replace. EC367001 BRAKE FLUID LEVEL INSPECTION 1. Place the master cylinder s ...

  • Yamaha YZ125N1 - page 71

    3-24 SPROCKETS INSPECTION/DRIVE CHAIN INSPECTION INSP ADJ EC368000 SPROCKETS INSPECTION 1. Inspect: 9 Sprocket teeth a Excessive wear → Replace. NOTE: Replace the drive, driven sprockets and drive chain as a set. EC369002 DRIVE CHAIN INSPECTION 1. Remove: 9 Master link clip 9 Joint 1 9 Drive chain 2 2. Clean: 9 Drive chain Place it in kerosene, a ...

  • Yamaha YZ125N1 - page 72

    3-25 DRIVE CHAIN SLACK ADJUSTMENT INSP ADJ EC36A060 DRIVE CHAIN SLACK ADJUSTMENT 1. Elevate the rear wheel by placing the suit- able stand under the engine. 2. Check: 9 Drive chain slack a Above the seal guard installation bolt. Out of specification → Adjust NOTE: Before checking and/or adjusting, rotate the rear wheel through several revolutions ...

  • Yamaha YZ125N1 - page 73

    3-26 FRONT FORK INSPECTION INSP ADJ 3. Adjust: 9 Drive chain slack EC36C000 FRONT FORK INSPECTION 1. Inspect: 9 Front fork smooth action Operate the front brake and stroke the front fork. Unsmooth action/oil leakage → Repair or replace. Drive chain slack adjustment steps: 9 Loosen the axle nut 1 and locknuts 2 . 9 Adjust chain slack by turning th ...

  • Yamaha YZ125N1 - page 74

    3-27 FRONT FORK OIL SEAL AND DUST SEAL CLEANING/ FRONT FORK REBOUND DAMPING FORCE ADJUSTMENT INSP ADJ Minimum 20 clicks out (from maximum position) EC36D001 FRONT FORK OIL SEAL AND DUST SEAL CLEANING 1. Remove: 9 Protector 9 Dust seal 1 NOTE: Use a thin screw driver , and be careful not to damage the inner fork tube and dust seal. 2. Clean: 9 Dust ...

  • Yamaha YZ125N1 - page 75

    3-28 FRONT FORK COMPRESSION DAMPING FORCE ADJUSTMENT INSP ADJ c C Do not force the adjuster past the minimum or maximum extent of adjustment. The ad- juster may be damaged. w Always adjust each front fork to the same setting. Uneven adjustment can cause poor handling and loss of stability . EC36J001 FRONT FORK COMPRESSION DAMPING FORCE ADJUSTMENT 1 ...

  • Yamaha YZ125N1 - page 76

    3-29 REAR SHOCK ABSORBER INSPECTION INSP ADJ 9 ST ANDARD POSITION: This is the position which is back by the spe- cific number of clicks from the fully turned-in position. c C Do not force the adjuster past the minimum or maximum extent of adjustment. The ad- juster may be damaged. w Always adjust each front fork to the same setting. Uneven adjustm ...

  • Yamaha YZ125N1 - page 77

    3-30 REAR SHOCK ABSORBER SPRING PRELOAD ADJUSTMENT INSP ADJ EC36M013 REAR SHOCK ABSORBER SPRING PRELOAD ADJUSTMENT 1. Elevate the rear wheel by placing the suit- able stand under the engine. 2. Remove: 9 Rear frame 3. Loosen: 9 Locknut 1 4. Adjust: 9 Spring preload By turning the adjuster 2 . NOTE: 9 Be sure to remove all dirt and mud from around t ...

  • Yamaha YZ125N1 - page 78

    3-31 REAR SHOCK ABSORBER REBOUND DAMPING FORCE ADJUSTMENT INSP ADJ EC36N014 REAR SHOCK ABSORBER REBOUND DAMPING FORCE ADJUSTMENT 1. Adjust: 9 Rebound damping force By turning the adjuster 1 . 9 ST ANDARD POSITION: This is the position which is back by the specif- ic number of clicks from the fully turned-in posi- tion. (Which align the punch mark a ...

  • Yamaha YZ125N1 - page 79

    3-32 REAR SHOCK ABSORBER LOW COMPRESSION DAMPING FORCE ADJUSTMENT INSP ADJ EC36c000 REAR SHOCK ABSORBER LOW COMPRESSION DAMPING FORCE ADJUSTMENT 1. Adjust: 9 Low compression damping force By turning the adjuster 1 . 9 ST ANDARD POSITION: This is the position which is back by the specif- ic number of clicks from the fully turned-in posi- tion. (Whic ...

  • Yamaha YZ125N1 - page 80

    3-33 REAR SHOCK ABSORBER LOW COMPRESSION DAMPING FORCE ADJUSTMENT INSP ADJ EC36d000 REAR SHOCK ABSORBER HIGH COMPRESSION DAMPING FORCE ADJUSTMENT 1. Adjust: 9 High compression damping force By turning the adjuster 1 . 9 ST ANDARD POSITION: This is the position which is back by the specif- ic number of turns from the fully turned-in posi- tion. (Whi ...

  • Yamaha YZ125N1 - page 81

    3-34 TIRE PRESSURE CHECK/SPOKES INSPECTION AND TIGHTENING/WHEEL INSPECTION INSP ADJ EC36Q000 TIRE PRESSURE CHECK 1. Measure: 9 T ire pressure Out of specification → Adjust. NOTE: 9 Check the tire while it is cold. 9 Loose bead stoppers allow the tire to slip off its position on the rim when the tire pressure is low . 9 A tilted tire valve stem in ...

  • Yamaha YZ125N1 - page 82

    3-35 STEERING HEAD INSPECTION AND ADJUSTMENT INSP ADJ 2. Inspect: 9 Bearing free play Exist play → Replace. EC36U013 STEERING HEAD INSPECTION AND ADJUSTMENT 1. Elevate the front wheel by placing a suitable stand under the engine. 2. Check: 9 Steering shaft Grasp the bottom of the forks and gently rock the fork assembly back and forth. Free play ? ...

  • Yamaha YZ125N1 - page 83

    3-36 STEERING HEAD INSPECTION AND ADJUSTMENT INSP ADJ 9 Loosen the ring nut one turn. 9 Retighten the ring nut using the ring nut wrench. w A void over-tightening. 9 Check the steering shaft by turning it lock to lock. If there is any binding, remove the steering shaft assembly and inspect the steering bearings. 9 Install the handle crown 5 , steer ...

  • Yamaha YZ125N1 - page 84

    3-37 LUBRICA TION INSP ADJ EC36a042 LUBRICA TION T o ensure smooth operation of all components, lubricate your machine during setup, after break- in, and after every race. 1 All control cable 2 Clutch lever pivot 3 Shift pedal pivot 4 Footrest pivot 5 Throttle-to-handlebar contact 6 Drive chain 7 Throttle roller sliding surface 8 T ube guide cable ...

  • Yamaha YZ125N1 - page 85

    3-38 ELECTRICAL/SP ARK PLUG INSPECTION INSP ADJ EC370000 ELECTRICAL EC371001 SP ARK PLUG INSPECTION 1. Remove: 9 Spark plug 2. Inspect: 9 Electrode 1 Wear/Damage → Replace. 9 Insulator color 2 Normal condition is a medium to light tan color . Distinctly different color → Check the engine condition. NOTE: When the engine runs for many hours at l ...

  • Yamaha YZ125N1 - page 86

    3-39 IGNITION TIMING CHECK INSP ADJ EC372051 IGNITION TIMING CHECK 1. Remove: 9 Cylinder head Refer to “CYLINDER HEAD, CYLINDER AND PISTON” section in the CHAPTER 4. 9 Crankcase cover (left) 2. Attach: 9 Dial gauge 1 9 Dial gauge stand 2 3. Rotate the magneto rotor 1 until the piston reaches top dead center (TDC). When this happens, the needle ...

  • Yamaha YZ125N1 - page 87

    3-40 IGNITION TIMING CHECK INSP ADJ 7. Adjust: 9 Ignition timing Adjustment steps: 9 Loosen the screws (stator) 1 . 9 Align the punch mark on the rotor with punch mark on the stator 2 by moving the stator . 9 T ighten the screws (stator). Screw (stator): 8 Nm (0.8 m•kg, 5.8 ft•lb) 5MV-9-10-3B 6/12/00 8:23 PM Page 21 ...

  • Yamaha YZ125N1 - page 88

    4-1 ENG SEA T , FUEL T ANK AND SIDE COVERS 4 EC400000 ENGINE EC4R0000 SEA T , FUEL T ANK AND SIDE COVERS Extent of removal Order Part name Q’ty Remarks SEAT, FUEL TANK AND SIDE COVERS REMOVAL Preparation for Turn the fuel cock to “OFF”. removal Disconnect the fuel hose. 1 Seat 1 2 Air scoop (left and right) 2 3 Fitting band 1 Remove on fuel t ...

  • Yamaha YZ125N1 - page 89

    4-2 ENG SEA T , FUEL T ANK AND SIDE COVERS 4 EC4R3000 REMOV AL POINTS EC413101 Side cover 1. Remove: 9 Side cover (left and right) 1 c C Be sure to remove the seat before remov- ing the side cover . If you remove the side cover with force without removing the seat, the panel 2 2 (on the inside) may contact the air cleaner case and come off. 5MV-9-1 ...

  • Yamaha YZ125N1 - page 90

    4-3 ENG EXHAUST PIPE AND SILENCER EC4S0000 EXHAUST PIPE AND SILENCER Extent of removal Order Part name Q’ty Remarks EXHAUST PIPE AND SILENCER REMOVAL Preparation for Side cover (right) Refer to “SEAT, FUEL TANK AND removal SIDE COVERS” section. 1 Bolt (silencer) 2 2 Silencer 1 3 Tension spring 2 4 Bolt (exhaust pipe) 2 5 Exhaust pipe 1 1 Exte ...

  • Yamaha YZ125N1 - page 91

    4-4 ENG RADIA TOR Extent of removal Order Part name Q’ty Remarks RADIATOR REMOVAL Preparation for Drain the coolant. Refer to “COOLANT REPLACEMENT“ removal section in the CHAPTER 3. Seat and fuel tank Refer to “SEAT, FUEL TANK AND SIDE COVERS” section. 1 Panel 2 Refer to ”REMOVAL POINTS“. 2 Clamp (radiator hose 1, 3) 2 Only loosening. ...

  • Yamaha YZ125N1 - page 92

    4-5 ENG RADIA TOR EC456000 HANDLING NOTE w Do not remove the radiator cap when the engine and radiator are hot. Scalding hot fluid and steam may be blown out under pressure, which could cause serious in- jury . When the engine has cooled, open the ra- diator cap by the following procedure: Place a thick rag, like a towel, over the radiator cap, slo ...

  • Yamaha YZ125N1 - page 93

    4-6 ENG RADIA TOR EC455000 ASSEMBL Y AND INST ALLA TION EC445341 Radiator 1. Install: 9 Radiator breather hose 1 9 Radiator hose 3 2 9 Radiator hose 1 3 T o radiator (right) 4 . NOTE: Install the radiator hose 3 with its shorter pro- truding length a from the protector 5 on the ra- diator side. 2. Install: 9 Radiator (right) 1 9 Bolt [radiator (rig ...

  • Yamaha YZ125N1 - page 94

    4-7 ENG CARBURETOR AND REED V AL VE EC460000 CARBURETOR AND REED V AL VE Extent of removal Order Part name Q’ty Remarks CARBURETOR AND REED VALVE REMOVAL Preparation for Fuel tank Refer to “SEAT, FUEL TANK AND removal SIDE COVERS” section. 1 Clamp (carburetor joint) 2 Loosen the screws (carburetor joint). 2 Carburetor 1 3 Carburetor joint 1 4 ...

  • Yamaha YZ125N1 - page 95

    4-8 ENG CARBURETOR AND REED V AL VE EC468000 CARBURETOR DISASSEMBL Y Extent of removal Order Part name Q’ty Remarks CARBURETOR DISASSEMBLY 1 Mixing chamber top 1 2 Throttle valve 1 Refer to “REMOVAL POINTS”. 3 Needle holder 1 4 Jet needle 1 5 Float chamber 1 6 Needle jet cover 1 7 Float pin 1 8 Float 1 9 Valve seat 1 0 Main jet 1 q Main jet h ...

  • Yamaha YZ125N1 - page 96

    4-9 ENG CARBURETOR AND REED V AL VE EC466030 HANDLING NOTE c C Do not disassemble the venturi block 1 1 and main nozzle 2 2 because it will cause a drop in carburetor performance. EC463000 REMOV AL POINTS EC463110 Throttle valve 1. Remove: 9 Throttle valve 1 9 Ring 2 9 Spring (throttle valve) 3 9 Mixing chamber top 4 9 Throttle cable 5 NOTE: While ...

  • Yamaha YZ125N1 - page 97

    4-10 ENG CARBURETOR AND REED V AL VE EC464200 Needle valve 1. Inspect: 9 Needle valve 1 9 V alve seat 2 Grooved wear a → Replace. Dust b → Clean. NOTE: Always replace the needle valve and valve seat as a set. EC464301 Throttle valve 1. Check: 9 Free movement Stick → Repair or replace. NOTE: Insert the throttle valve 1 into the carburetor body ...

  • Yamaha YZ125N1 - page 98

    4-11 ENG CARBURETOR AND REED V AL VE Measurement and adjustment steps: 9 Remove the drain plug. 9 Connect the fuel level gauge adapter 2 and fuel level gauge 1 to the float chamber . Fuel level gauge adapter: YM-01470/90890-01470 Fuel level gauge: YM-1312-A/90890-01312 9 Hold the fuel level gauge vertically next to the float chamber mating surface. ...

  • Yamaha YZ125N1 - page 99

    4-12 ENG CARBURETOR AND REED V AL VE 9 V alve stopper height b Out of specification → Adjust stopper/ Replace valve stopper . EC465000 ASSEMBL Y AND INST ALLA TION EC465190 Reed valve 1. Install: 9 Reed valve 1 9 Stopper (reed valve) 2 9 Screw (reed valve) 3 NOTE: 9 Install the reed valve with the reed valve bend- ing as shown. 9 Note the cut a i ...

  • Yamaha YZ125N1 - page 100

    4-13 ENG CARBURETOR AND REED V AL VE 2. Install: 9 Reed valve assembly 1 9 Reed valve spacer 2 NOTE: Install the reed valve spacer with its wider con- tact surface side a to the right. 3. Install: 9 Carburetor joint 1 9 Bolt (carburetor joint) 2 EC4652C2 Carburetor 1. Install: 9 Throttle stop screw 1 9 Locknut 2 9 Pilot air screw 3 Pilot air screw: ...

  • Yamaha YZ125N1 - page 101

    4-14 ENG CARBURETOR AND REED V AL VE 3. Install: 9 Main jet holder 1 9 Main jet 2 9 Pilot jet 3 9 V alve seat 4 9 Screw (valve seat) 5 4. Install: 9 Needle valve 1 9 Float 2 9 Float pin 3 9 Screw (float pin) 4 9 Needle jet cover 5 NOTE: 9 After installing the needle valve to the float, in- stall them to the carburetor . 9 Check the float for smooth ...

  • Yamaha YZ125N1 - page 102

    4-15 ENG CARBURETOR AND REED V AL VE 7. Install: 9 Throttle cable 1 9 Mixing chamber top 2 9 Spring (throttle valve) 3 9 Ring 4 9 Throttle valve 5 NOTE: 9 While compressing the spring, connect the throttle cable. 9 Align the projection a on the ring with the groove b in the needle holder 6 . 8. Install: 9 Mixing chamber top 1 9 Screw (mixing chambe ...

  • Yamaha YZ125N1 - page 103

    4-16 ENG CARBURETOR AND REED V AL VE 2. T ighten: 9 Screw (air filter joint) 1 9 Screw (carburetor joint) 2 3. Clamp: 9 Air vent hose 1 9 Overflow hose 2 Refer to “CABLE ROUTING DIAGRAM” section in the CHAPTER 2. 4. Adjust: 9 Idle speed Refer to “IDLE SPEED ADJUSTMENT” section in the CHAPTER 3. 5MV-9-10-4A 6/12/00 8:17 PM Page 17 ...

  • Yamaha YZ125N1 - page 104

    4-17 ENG CYLINDER HEAD, CYLINDER AND PISTON EC470000 CYLINDER HEAD, CYLINDER AND PISTON EC478000 CYLINDER HEAD AND CYLINDER Extent of removal Order Part name Q’ty Remarks CYLINDER HEAD AND CYLINDER REMOVAL Preparation for Seat and fuel tank Refer to “SEAT, FUEL TANK AND removal SIDE COVERS” section. Exhaust pipe and silencer Refer to ”EXHAU ...

  • Yamaha YZ125N1 - page 105

    4-18 ENG CYLINDER HEAD, CYLINDER AND PISTON EC478100 PISTON AND POWER V AL VE Extent of removal Order Part name Q’ty Remarks PISTON AND POWER VALVE REMOVAL 1 Piston pin clip 2 2 Piston pin 1 3 Piston 1 Refer to “REMOVAL POINTS”. 4 Small end bearing 1 5 Piston ring 1 6 Power valve cover 1 7 Thrust plate 1 8 Bolt (link lever) 1 9 Valve shaft 1 ...

  • Yamaha YZ125N1 - page 106

    4-19 ENG CYLINDER HEAD, CYLINDER AND PISTON EC473000 REMOV AL POINTS EC473210 Push rod 1. Remove: 9 Bolt (push rod) 1 9 Push rod 2 NOTE: Set the collar 3 included in owner ’s tool kit to remove the bolt (push rod). EC473401 Piston and piston ring 1. Remove: 9 Piston pin clip 1 NOTE: Before removing the piston pin clip, cover the crankcase with a ...

  • Yamaha YZ125N1 - page 107

    4-20 ENG CYLINDER HEAD, CYLINDER AND PISTON EC474000 INSPECTION EC474101 Cylinder head 1. Remove: 9 Carbon deposits Use a rounded scraper 1 . NOTE: T ake care to avoid damaging the spark plug threads. Do not use a sharp instrument. Avoid scratching the aluminum. 2. Inspect: 9 Cylinder head water jacket Crust of minerals/Rust → Remove. 9 Cylinder ...

  • Yamaha YZ125N1 - page 108

    4-21 ENG CYLINDER HEAD, CYLINDER AND PISTON EC474301 Piston 1. Remove: 9 Carbon deposits From the piston crown a and ring groove b . 2. Inspect: 9 Piston wall Score marks → Repair or replace. 3. Measure: 9 Piston skirt diameter Use micrometer 1 . Measure the specific distance a from the bottom edge. Out of specification → Replace. 2. Inspect: 9 ...

  • Yamaha YZ125N1 - page 109

    4-22 ENG CYLINDER HEAD, CYLINDER AND PISTON EC474402 Piston pin and small end bearing 1. Inspect: 9 Piston pin 9 Small end bearing Signs of heat discoloration → Replace. 2. Measure: 9 Piston pin outside diameter Use micrometer 1 . Out of limit → Replace. 3. Check: 9 Free play (when the piston pin 1 is in place in the piston 2 ) There should be ...

  • Yamaha YZ125N1 - page 110

    4-23 ENG CYLINDER HEAD, CYLINDER AND PISTON EC474502 Piston ring 1. Install: 9 Piston ring Into the cylinder . Push the ring with the piston crown. 2. Measure: 9 End gap Use a thickness gauge 1 . Out of limit → Replace. 3. Measure: 9 Side clearance Use a thickness gauge 1 . Out of limit → Replace piston and/or ring. NOTE: Check at several point ...

  • Yamaha YZ125N1 - page 111

    4-24 ENG CYLINDER HEAD, CYLINDER AND PISTON EC474700 Combination of piston and cylinder 1. Check: 9 Cylinder mark a 2. Check: 9 Piston mark a 3. Combination: Combine the piston and cylinder by the fol- lowing chart. NOTE: When you purchase a cylinder , you cannot des- ignate its size. Choose the piston that matches the above chart. Piston clearance ...

  • Yamaha YZ125N1 - page 112

    4-25 ENG CYLINDER HEAD, CYLINDER AND PISTON EC474830 Power valve 1. Inspect: 9 Power valve 1,2 1 Wear/Damage → Replace. Carbon deposits → Remove. 9 Link lever 2 9 V alve shaft 3 9 Collar 4 Wear/Damage → Replace. 9 Spring 5 Broken → Replace. EC474901 Power valve hole on cylinder 1. Remove: 9 Carbon deposits From power valve hole surface a . ...

  • Yamaha YZ125N1 - page 113

    4-26 ENG CYLINDER HEAD, CYLINDER AND PISTON 2. Install: 9 Spring 1 9 Link lever 2 9 Collar 3 9 V alve shaft 4 9 Bolt (link lever) 5 NOTE: 9 Install the spring to the link lever , and then to the cylinder . 9 Install the spring with its stopper portion a fac- ing inward. 9 Apply the lithium soap base grease on the oil seal lip. 3. Install: 9 Thrust ...

  • Yamaha YZ125N1 - page 114

    4-27 ENG CYLINDER HEAD, CYLINDER AND PISTON EC475233 Piston ring and piston 1. Install: 9 Piston ring 1 NOTE: 9 T ake care not to scratch the piston or damage the piston ring. 9 Align the piston ring gap with the pin 2 . 9 After installing the piston ring, check the smooth movement of it. 2. Install: 9 Gasket (cylinder) 1 9 Small end bearing 2 9 Do ...

  • Yamaha YZ125N1 - page 115

    4-28 ENG CYLINDER HEAD, CYLINDER AND PISTON 3. Install: 9 Nut (cylinder) 1 NOTE: T ighten the nuts in stage, using a crisscross pat- tern. 4. Install: 9 Collar 1 9 Push rod 2 9 Plain washer 3 9 Bolt (push rod) 4 NOTE: 9 Set the collar 5 included in owner's tool kit to install the bolt (push rod). 9 Do not forget to remove the collar . EC4753A1 ...

  • Yamaha YZ125N1 - page 116

    4-29 ENG CYLINDER HEAD, CYLINDER AND PISTON 7. Install: 9 Cylinder head 1 9 Copper washer 2 9 Nut (cylinder head) 3 NOTE: T ighten the nuts (cylinder head) in stage, using a crisscross pattern. 8. Install: 9 Engine bracket 1 9 Bolt (engine bracket) 2 9 CDI unit bracket 3 9 Engine mounting bolt (upper) 4 9. Install: 9 Spark plug 1 9 Spark plug cap 2 ...

  • Yamaha YZ125N1 - page 117

    4-30 ENG CLUTCH AND PRIMAR Y DRIVEN GEAR Extent of removal Order Part name Q’ty Remarks CLUTCH PLATE AND FRICTION PLATE REMOVAL Preparation for Drain the transmission oil. Refer to “TRANSMISSION OIL REPLACE- removal MENT “ section in the CHAPTER 3. Bolt (brake pedal) Shift the brake pedal downward. Clutch cable Disconnect at engine side. 1 Cl ...

  • Yamaha YZ125N1 - page 118

    4-31 ENG CLUTCH AND PRIMAR Y DRIVEN GEAR EC498100 PRIMAR Y DRIVEN GEAR Extent of removal Order Part name Q’ty Remarks PRIMARY DRIVEN GEAR REMOVAL 1 Nut (clutch boss) 1 Use special tool. 2 Lock washer 1 Refer to “REMOVAL POINTS”. 3 Clutch boss 1 4 Plain washer [ φ 34 mm (1.34 in)] 1 5 Primary driven gear 1 6 Bearing 1 7 Thrust plate [ φ 36 m ...

  • Yamaha YZ125N1 - page 119

    4-32 ENG CLUTCH AND PRIMAR Y DRIVEN GEAR EC493000 REMOV AL POINTS EC483211 Clutch boss 1. Remove: 9 Nut 1 9 Lock washer 2 9 Clutch boss 3 NOTE: Straighten the lock washer tab and use the clutch holding tool 4 , 5 to hold the clutch boss. å For USA and CDN ∫ Except for USA and CDN EC494000 INSPECTION EC484100 Clutch housing and boss 1. Inspect: 9 ...

  • Yamaha YZ125N1 - page 120

    4-33 ENG CLUTCH AND PRIMAR Y DRIVEN GEAR EC484500 Friction plate 1. Measure: 9 Friction plate thickness Out of specification → Replace friction plate as a set. Measure at all four points. EC484600 Clutch plate 1. Measure: 9 Clutch plate warpage Out of specification → Replace clutch plate as a set. Use a surface plate 1 and thickness gauge 2 . E ...

  • Yamaha YZ125N1 - page 121

    4-34 ENG CLUTCH AND PRIMAR Y DRIVEN GEAR EC495000 ASSEMBL Y AND INST ALLA TION EC495240 Clutch 1. Install: 9 Thrust plate [ φ 36 mm (1.42 in)] 1 9 Spacer 2 9 Bearing 3 9 Primary driven gear 4 NOTE: Apply the transmission oil on the spacer , bearing and primary driven gear inner circumference. 2. Install: 9 Plain washer [ φ 34 mm (1.34 in)] 1 9 Cl ...

  • Yamaha YZ125N1 - page 122

    4-35 ENG CLUTCH AND PRIMAR Y DRIVEN GEAR 5. Install: 9 Friction plate 1 1 9 Clutch plate 2 9 Friction plate 2 3 NOTE: 9 Install the clutch plates and friction plates alter- nately on the clutch boss, starting with a friction plate and ending with a friction plate. 9 Use the friction plates 1 for the first and final while paying attention to the dif ...

  • Yamaha YZ125N1 - page 123

    4-36 ENG CLUTCH AND PRIMAR Y DRIVEN GEAR EC495121 Push lever 1. Install: 9 T orsion spring 1 9 Push lever 2 T o push lever axle 3 . NOTE: 9 Install the push lever with its 5 mark a down- ward. 9 T emporarily install the torsion spring and push lever at this point. 2. Check: 9 Push lever position NOTE: When pushing the push lever forward, the front ...

  • Yamaha YZ125N1 - page 124

    4-37 ENG CLUTCH AND PRIMAR Y DRIVEN GEAR 4. Install: 9 Plain washer 1 9 Circlip 2 5MV-9-10-4B 6/12/00 8:40 PM Page 18 ...

  • Yamaha YZ125N1 - page 125

    4-38 ENG KICK AXLE, SHIFT SHAFT AND PRIMAR Y DRIVE GEAR Extent of removal Order Part name Q’ty Remarks RPIMARY DRIVE GEAR REMOVAL Preparation for Drain the transmission oil. Refer to “TRANSMISSION OIL REPLACE- removal MENT“ section in the CHAPTER 3. Clutch cable Disconnect at engine side. Bolt (brake pedal) Shift the brake pedal downward. Rad ...

  • Yamaha YZ125N1 - page 126

    4-39 ENG KICK AXLE, SHIFT SHAFT AND PRIMAR Y DRIVE GEAR EC4C8100 KICK AXLE AND SHIFT SHAFT Extent of removal Order Part name Q’ty Remarks KICK AXLE AND SHIFT SHAFT REMOVAL 1 Kick idle gear 1 2 kick axle assembly 1 Refer to “REMOVAL POINTS”. 3 Shift pedal 1 4 Shift shaft 1 5 Roller 1 6 Shift guide 1 7 Shift lever assembly 1 Refer to “REMOVAL ...

  • Yamaha YZ125N1 - page 127

    4-40 ENG KICK AXLE, SHIFT SHAFT AND PRIMAR Y DRIVE GEAR EC4C3000 REMOV AL POINTS EC483111 Primary drive gear 1. Loosen: 9 Bolt (primary drive gear) 1 NOTE: Place an aluminum plate a between the teeth of the primary drive gear 2 and driven gear 3 . EC4B3101 Kick axle assembly 1. Remove: 9 Kick axle assembly 1 NOTE: Unhook the torsion spring 2 from t ...

  • Yamaha YZ125N1 - page 128

    4-41 ENG KICK AXLE, SHIFT SHAFT AND PRIMAR Y DRIVE GEAR EC4B4300 Kick gear clip 1. Measure: 9 Kick clip friction force Out of specification → Replace. Use a spring gauge 1 . EC4B4400 Shift shaft 1. Inspect: 9 Shift shaft 1 Bend/Damage → Replace. 9 Spring 2 Broken → Replace. EC4C4100 Shift guide and shift lever assembly 1. Inspect: 9 Shift gui ...

  • Yamaha YZ125N1 - page 129

    4-42 ENG KICK AXLE, SHIFT SHAFT AND PRIMAR Y DRIVE GEAR EC4C5000 ASSEMBL Y AND INST ALLA TION EC4C5120 Stopper lever 1. Install: 9 T orsion spring 1 9 Stopper lever 2 9 Spacer 3 9 Bolt (stopper lever) 4 NOTE: 9 Align the stopper lever roller with the slot on segment. 9 When installing the stopper lever , make sure that the torsion spring is in the ...

  • Yamaha YZ125N1 - page 130

    4-43 ENG KICK AXLE, SHIFT SHAFT AND PRIMAR Y DRIVE GEAR 4. Install: 9 Bolt (shift guide) 1 EC4C5301 Shift shaft 1. Install: 9 Roller 1 9 Shift shaft 2 NOTE: Apply the transmission oil on the roller and shift shaft. EC4B5302 Kick axle assembly 1. Install: 9 Kick gear 1 9 Plain washer 2 9 T orsion spring 3 T o kick axle 4 . NOTE: Make sure the stoppe ...

  • Yamaha YZ125N1 - page 131

    4-44 ENG KICK AXLE, SHIFT SHAFT AND PRIMAR Y DRIVE GEAR 4. Hook: 9 T orsion spring 1 NOTE: T urn the torsion spring clockwise and hook into the proper hole a in the crankcase. EC4C5402 Kick idle gear 1. Install: 9 Circlip 1 9 Kick idle gear 2 9 Plain washer 3 NOTE: 9 Apply the transmission oil on the kick idle gear inner circumference. 9 Install th ...

  • Yamaha YZ125N1 - page 132

    4-45 ENG KICK AXLE, SHIFT SHAFT AND PRIMAR Y DRIVE GEAR 5. Install: 9 Crankcase cover (right) 1 NOTE: 9 Position the rack a on the push rod backward. 9 Mesh the governor gear 2 , and impeller shaft gear 3 with primary drive gear 4 . 6. Install: 9 Bolt [crankcase cover (right)] 1 NOTE: T ighten the bolts in stage, using a crisscross pattern. 7. Inst ...

  • Yamaha YZ125N1 - page 133

    4-46 ENG YPVS GOVERNOR Extent of removal Order Part name Q’ty Remarks YPVS GOVERNOR REMOVAL Preparation for Crankcase cover (right) Refer to “KICK AXLE, SHIFT SHAFT AND removal PRIMARY DRIVE GEAR” section. 1 Governor assembly 1 2 Dowel pin 1 Refer to “REMOVAL POINTS”. 3 Retainer 1 4 Ball 4 5 Retainer weight 1 6 Plain washer 4 7 Thrust bea ...

  • Yamaha YZ125N1 - page 134

    4-47 ENG YPVS GOVERNOR EC4K3000 REMOV AL POINTS EC4K3100 Governor 1. Remove: 9 Dowel pin 1 NOTE: While compressing the spring, remove the dowel pin. EC4K4000 INSPECTION EC4K4100 Governor groove 1. Inspect: 9 Plain washer 1 9 Collar 2 Wear/Damage → Replace. EC4K4200 Bearing 1. Inspect: 9 Thrust bearing 1 9 Plain washer 2 Wear/Damage → Replace. E ...

  • Yamaha YZ125N1 - page 135

    4-48 ENG YPVS GOVERNOR 2. Install: 9 Ball 1 9 Retainer 2 T o governor shaft 3 . NOTE: Apply the transmission oil on the retainer and ball. 3. Install: 9 Dowel pin 1 NOTE: 9 While compressing the spring, install the dowel pin. 9 Make sure the dowel pin fits into the groove a in the retainer . 4. Install: 9 Governor assembly 1 NOTE: Align the groove ...

  • Yamaha YZ125N1 - page 136

    4-49 ENG W A TER PUMP Extent of removal Order Part name Q’ty Remarks WATER PUMP DISASSEMBLY Preparation for Crankcase cover (right) Refer to “KICK AXLE, SHIFT SHAFT AND removal PRIMARY DRIVE GEAR” section. 1 Water pump housing cover 1 2 Impeller 1 3 Plain washer 1 R efer to “REMOVAL POINTS”. 4 Impeller shaft 1 5 Bearing 1 6 Oil seal 2 Ref ...

  • Yamaha YZ125N1 - page 137

    4-50 ENG W A TER PUMP EC4G3000 REMOV AL POINTS EC4G3110 Impeller shaft 1. Remove: 9 Impeller 1 9 Plain washer 2 9 Impeller shaft 3 NOTE: Hold the impeller shaft on its width across the flats a with spanners, etc. and remove the im- peller . EC4G3210 Oil seal NOTE: It is not necessary to disassemble the water pump, unless there is an abnormality suc ...

  • Yamaha YZ125N1 - page 138

    4-51 ENG W A TER PUMP EC444300 Impeller shaft gear 1. Inspect: 9 Gear teeth a Wear/Damage → Replace. EC4H4600 Bearing 1. Inspect: 9 Bearing 1 Rotate inner race with a finger . Rough spot/Seizure → Replace. EC444400 Oil seal 1. Inspect: 9 Oil seal 1 Wear/Damage → Replace. EC4G5000 ASSEMBL Y AND INST ALLA TION EC4G5111 Oil seal 1. Install: 9 Oi ...

  • Yamaha YZ125N1 - page 139

    4-52 ENG W A TER PUMP EC4G5220 Impeller shaft 1. Install: 9 Impeller shaft 1 NOTE: 9 T ake care so that the oil seal lip is not dam- aged or the spring does not slip off its position. 9 When installing the impeller shaft, apply the lithium soap base grease on the oil seal lip and impeller shaft. And install the shaft while turn- ing it. 2. Install: ...

  • Yamaha YZ125N1 - page 140

    4-53 ENG CDI MAGNETO Extent of removal Order Part name Q’ty Remarks CDI MAGNETO REMOVAL Preparation for Seat and fuel tank Refer to “SEAT, FUEL TANK AND removal SIDE COVERS” section. Bolt [Radiator (left)] Refer to “RADIATOR” section. Disconnect the CDI magneto lead. 1 Crankcase cover (left) 1 2 Nut (rotor) 1 Use special tool. 3 Rotor 1 R ...

  • Yamaha YZ125N1 - page 141

    4-54 ENG CDI MAGNETO EC4L3000 REMOV AL POINTS EC4L3102 Rotor 1. Remove: 9 Nut (rotor) 1 9 Plain washer 2 Use the rotor holding tool 3 . 2. Remove: 9 Rotor 1 Use the flywheel puller 2 . NOTE: When installing the flywheel puller , turn it coun- terclockwise. EC4L4000 INSPECTION EC4L4101 CDI magneto 1. Inspect: 9 Rotor inner surface a 9 Stator outer s ...

  • Yamaha YZ125N1 - page 142

    4-55 ENG CDI MAGNETO 2. Install: 9 Woodruf f key 1 9 Rotor 2 NOTE: 9 Clean the tapered portions of the crankshaft and rotor . 9 When installing the woodruff key , make sure that its flat surface a is in parallel with the crankshaft center line b . 9 When installing the rotor , align the keyway c of the rotor with the woodruff key . 3. Install: 9 Pl ...

  • Yamaha YZ125N1 - page 143

    4-56 ENG CDI MAGNETO 7. Connect: 9 CDI magneto lead 1 Refer to “CABLE ROUTING DIAGRAM” section in the CHAPTER 2. 8. Install: 9 Gasket [crankcase cover (left)] 9 Crankcase cover (left) 1 9 Screw [crankcase cover (left)] 2 NOTE: T ighten the screws in stage, using a crisscross pattern. 8. Install: 9 Gasket [crankcase cover (left)] 9 Crankcase cov ...

  • Yamaha YZ125N1 - page 144

    4-57 ENG ENGINE REMOV AL Extent of removal Order Part name Q’ty Remarks ENGINE REMOVAL Preparation for Hold the machine by placing the removal suitable stand under the engine. Seat and fuel tank Refer to “SEAT, FUEL TANK AND SIDE COVERS” section. Carburetor Refer to “CARBURETOR AND REED VALVE” section. Exhaust pipe and silencer Refer to ? ...

  • Yamaha YZ125N1 - page 145

    4-58 ENG ENGINE REMOV AL Extent of removal: 1 Engine removal Extent of removal Order Part name Q’ty Remarks 1 Chain cover 1 2 Nut (drive sprocket) 1 3 Lock washer 1 Refer to “REMOVAL POINTS”. 4 Drive sprocket 1 5 Clip 1 6 Bolt (brake pedal) 1 7 Brake pedal 1 8 Engine bracket 2 9 Engine mounting bolt 3 10 Pivot shaft 1 Refer to “REMOVAL POIN ...

  • Yamaha YZ125N1 - page 146

    4-59 ENG ENGINE REMOV AL EC4M3000 REMOV AL POINTS EC4F3100 Drive sprocket 1. Remove: 9 Nut (drive sprocket) 1 9 Lock washer 2 NOTE: 9 Straighten the lock washer tab. 9 Loosen the nut while applying the rear brake. 2. Remove: 9 Drive sprocket 1 9 Drive chain 2 NOTE: Remove the drive sprocket together with the dri- ve chain. EC4M3301 Engine removal 1 ...

  • Yamaha YZ125N1 - page 147

    4-60 ENG ENGINE REMOV AL EC4M5000 ASSEMBL Y AND INST ALLA TION EC4M5171 Engine installation 1. Install: 9 Engine 1 Install the engine from right side. 9 Pivot shaft 2 9 Engine mounting bolt (lower) 3 9 Engine mounting bolt (front) 4 9 Engine bracket 5 9 Bolt (engine bracket) 6 9 CDI unit bracket 7 9 Engine mounting bolt (upper) 8 NOTE: Apply the mo ...

  • Yamaha YZ125N1 - page 148

    4-61 ENG ENGINE REMOV AL 2. Install: 9 Lock washer 1 9 Nut (drive sprocket) 2 NOTE: T ighten the nut while applying the rear brake. 3. Bend the lock washer tab to lock the nut. 4. Install: 9 Chain cover 1 9 Screw (chain cover) 2 5 Nm (0.5 m•kg, 3.6 ft•lb) 60 Nm (6.0 m•kg, 43 ft•lb) 5MV-9-10-4C 6/12/00 8:34 PM Page 22 ...

  • Yamaha YZ125N1 - page 149

    4-62 ENG CRANKCASE AND CRANKSHAFT Extent of removal Order Part name Q’ty Remarks CRANKCASE AND CRANKSHAFT REMOVAL Preparation for Engine Refer to “ ENGINE REMOVAL” section. removal Piston Refer to “ CYLINDER HEAD, CYLINDER AND PISTON ” section. Primary drive gear Kick idle gear Refer to “ KICK AXLE, SHIFT SHAFT AND Stopper lever PRIMARY ...

  • Yamaha YZ125N1 - page 150

    4-63 ENG CRANKCASE AND CRANKSHAFT EC4N3000 REMOV AL POINTS EC4N3100 Segment 1. Remove: 9 Bolt (segment) 1 9 Segment 2 NOTE: T urn the segment counterclockwise until it stops and loosen the bolt. EC4N3211 Crankcase 1. Remove: 9 Crankcase (right) 1 Use the crankcase separating tool 2 and crankcase separating bolt 3 . NOTE: 9 Fully tighten the tool ho ...

  • Yamaha YZ125N1 - page 151

    4-64 ENG CRANKCASE AND CRANKSHAFT EC4N3301 Crankshaft 1. Remove: 9 Crankshaft 1 Use the crankcase separating tool 2 and crankcase separating bolt 3 . c C Do not use a hammer to drive out the crankshaft. EC4N3401 Crankshaft bearing 1. Remove: 9 Bearing 1 NOTE: 9 Remove the bearing from the crankcase by pressing its inner race as shown in å . 9 If t ...

  • Yamaha YZ125N1 - page 152

    4-65 ENG CRANKCASE AND CRANKSHAFT Standard <Limit> Runout 0.03 mm 0.05 mm limit: (0.0012 in) (0.0020 in) Small end 0.8~1.0 mm 2.0 mm free play: (0.031~0.039 in) (0.08 in) Side 0.20~0.70 mm — clearance: (0.008~0.028in) Crank 55.90~55.95 mm — width: (2.201~2.203 in) 2. Inspect: 9 Bearings 1 Rotate inner race with a finger . Rough spot/Seizu ...

  • Yamaha YZ125N1 - page 153

    4-66 ENG CRANKCASE AND CRANKSHAFT EC4N5102 Oil seal 1. Install: 9 Oil seal (left) 1 9 Oil seal (right) 2 NOTE: 9 Apply the lithium soap base grease on the oil seal lip. 9 Install the oil seal with its manufacture’s marks or numbers facing outward. EC4N5272 Crankshaft 1. Install: 9 Crankshaft 1 Use the crankshaft installing tool 2 , 3 , 4 å For U ...

  • Yamaha YZ125N1 - page 154

    4-67 ENG CRANKCASE AND CRANKSHAFT 2. Check: 9 Shifter operation 9 T ransmission operation Unsmooth operation → Repair . 3. Apply: 9 Sealant On the crankcase (right) 1 NOTE: Clean the contacting surface of crankcase (left and right) before applying the sealant. 4. Install: 9 Dowel pin 1 9 O-ring 2 9 Crankcase (right) 3 T o crankcase (left) 4 . NOT ...

  • Yamaha YZ125N1 - page 155

    4-68 ENG CRANKCASE AND CRANKSHAFT 6. Install: 9 Holder 1 9 Bolt (holder) 2 7. Install: 9 Segment 1 9 Bolt (segment) 2 NOTE: 9 When installing the segment onto the shift cam 3 , align the punch mark a with the dowel pin b . 9 T urn the segment clockwise until it stops and tighten the bolt. 8. Remove: 9 Sealant Forced out on the cylinder mating surfa ...

  • Yamaha YZ125N1 - page 156

    4-69 ENG TRANSMISSION, SHIFT CAM AND SHIFT FORK Extent of removal Order Part name Q’ty Remarks TRANSMISSION, SHIFT CAM AND SHIFT FORK REMOVAL Preparation for Engine Refer to “ ENGINE REMOVAL” section. removal Separate the crankcase. Ref er t o “CRANKCASE AND CRANK SHAFT ” section. 1 Guide bar (long) 1 2 Guide bar (short) 1 3 Shift cam 1 4 ...

  • Yamaha YZ125N1 - page 157

    4-70 ENG TRANSMISSION, SHIFT CAM AND SHIFT FORK EC4H3000 REMOV AL POINTS EC4H3200 T ransmission 1. Remove: 9 Main axle 1 9 Drive axle 2 NOTE: 9 T ap lightly on the transmission drive axle with a soft hammer to remove. 9 Remove assembly carefully . Note the position of each part. Pay particular attention to the lo- cation and direction of shift fork ...

  • Yamaha YZ125N1 - page 158

    4-71 ENG TRANSMISSION, SHIFT CAM AND SHIFT FORK EC4H4801 Shift fork, shift cam and segment 1. Inspect: 9 Shift fork 1 Wear/Damage/Scratches → Replace. 2. Inspect: 9 Shift cam 1 9 Segment 2 9 Guide bar 3 Bend/Wear/Damage → Replace. 3. Check: 9 Shift fork movement On its guide bar . Unsmooth operation → Replace shift fork and/or guide bar . NOT ...

  • Yamaha YZ125N1 - page 159

    4-72 ENG TRANSMISSION, SHIFT CAM AND SHIFT FORK 2. Install: 9 2nd wheel gear (28T) 1 9 6th wheel gear (24T) 2 9 4th wheel gear (27T) 3 9 3rd wheel gear (26T) 4 9 5th wheel gear (26T) 5 9 1st wheel gear (30T) 6 T o drive axle 7 . NOTE: 9 Apply the molybdenum disulfide oil on the 1st, 2nd, 3rd and 4th wheel gears inner circumfer- ence. 9 Apply the tr ...

  • Yamaha YZ125N1 - page 160

    4-73 ENG TRANSMISSION, SHIFT CAM AND SHIFT FORK EC4H5331 Shift cam and shift fork 1. Install: 9 Shift fork 1 (L) 1 9 Shift fork 2 2 9 Shift fork 3 (R) 3 NOTE: 9 Mesh the shift fork #1 (L) with the 6th wheel gear 4 and #3 (R) with the 5th wheel gear 6 on the drive axle. 9 Mesh the shift fork #2 with the 3rd/4th pinion gear 5 on the main axle. 2. Ins ...

  • Yamaha YZ125N1 - page 161

    5-1 CHAS FRONT WHEEL AND REAR WHEEL 5 Extent of removal Order Part name Q’ty Remarks FRONT WHEEL REMOVAL Preparation for Hold the machine by placing the removal suitable stand under the engine. 1 Hose cover 1 2 Bolt (brake hose holder) 2 Only loosening. 3 Bolt (axle holder) 4 Only loosening. 4 Nut (front wheel axle) 1 5 Front wheel axle 1 6 Front ...

  • Yamaha YZ125N1 - page 162

    5-2 CHAS FRONT WHEEL AND REAR WHEEL 5 EC598100 REAR WHEEL Extent of removal: 1 Rear wheel removal 2 Wheel bearing removal 3 Brake disc removal Extent of removal Order Part name Q’ty Remarks REAR WHEEL REMOVAL Preparation for Hold the machine by placing the removal suitable stand under the engine. 1 Nut (rear wheel axle) 1 2 Rear wheel axle 1 3 Ch ...

  • Yamaha YZ125N1 - page 163

    5-3 CHAS FRONT WHEEL AND REAR WHEEL EC593000 REMOV AL POINTS EC523101 Rear wheel 1. Remove: 9 Wheel 1 NOTE: Push the wheel forward and remove the drive chain 2 . EC513201 Wheel bearing (if necessary) 1. Remove: 9 Bearing 1 NOTE: Remove the bearing using a general bearing puller 2 . EC594000 INSPECTION EC514100 Wheel 1. Measure: 9 Wheel runout Out o ...

  • Yamaha YZ125N1 - page 164

    5-4 CHAS FRONT WHEEL AND REAR WHEEL EC514200 Wheel axle 1. Measure: 9 Wheel axle bends Out of specification → Replace. Use the dial gauge 1 . NOTE: The bending value is shown by one half of the dial gauge reading. w Do not attempt to straighten a bent axle. EC594200 Brake disc 1. Measure: 9 Brake disc deflection (only rear brake disc) Use the dia ...

  • Yamaha YZ125N1 - page 165

    5-5 CHAS FRONT WHEEL AND REAR WHEEL EC595000 ASSEMBL Y AND INST ALLA TION EC595101 Front wheel 1. Install: 9 Bearing (left) 1 9 Spacer 2 9 Bearing (right) 3 9 Oil seal 4 NOTE: 9 Apply the lithium soap base grease on the bearing and oil seal lip when installing. 9 Use a socket that matches the outside diam- eter of the race of the bearing. 9 Left si ...

  • Yamaha YZ125N1 - page 166

    5-6 CHAS FRONT WHEEL AND REAR WHEEL 5. Install: 9 Wheel axle 1 NOTE: Apply the lithium soap base grease on the wheel axle. 6. Install: 9 Nut (wheel axle) 1 7. T ighten: 9 Bolt (axle holder) 1 NOTE: Before tightening the bolt, fit the wheel axle to the axle holder by stroking the front fork several times with the front brake applied. 8. Install: 9 B ...

  • Yamaha YZ125N1 - page 167

    5-7 CHAS FRONT WHEEL AND REAR WHEEL EC5251A0 Rear wheel 1. Install: 9 Bearing (right) 1 9 Circlip 2 9 Spacer 3 9 Bearing (left) 4 9 Oil seal 5 NOTE: 9 Apply the lithium soap base grease on the bearing and oil seal lip when installing. 9 Install the bearing with seal facing outward. 9 Use a socket that matches the outside diam- eter of the race of t ...

  • Yamaha YZ125N1 - page 168

    5-8 CHAS FRONT WHEEL AND REAR WHEEL 3. Install: 9 Driven sprocket 1 9 Bolt (driven sprocket) 2 9 Plain washer (driven sprocket) 3 9 Nut (driven sprocket) 4 NOTE: T ighten the nuts in stage, using a crisscross pat- tern. 4. Install: 9 Collar 1 NOTE: Apply the lithium soap base grease on the oil seal lip. 5. Install: 9 Wheel NOTE: Install the brake d ...

  • Yamaha YZ125N1 - page 169

    5-9 CHAS FRONT WHEEL AND REAR WHEEL 8. Install: 9 Chain puller (right) 1 9 Plain washer 2 9 Nut (wheel axle) 3 NOTE: T emporarily tighten the nut (wheel axle) at this point. 9. Adjust: 9 Drive chain slack a Refer to “DRIVE CHAIN SLACK ADJUSTMENT” section in the CHAPTER 3. 10. T ighten: 9 Nut (wheel axle) 1 9 Locknut 2 125 Nm (12.5 m•kg, 90 ft ...

  • Yamaha YZ125N1 - page 170

    5-10 CHAS FRONT BRAKE AND REAR BRAKE Extent of removal Order Part name Q’ty Remarks FRONT BRAKE REMOVAL Preparation for Hold the machine by placing the removal suitable stand under the engine. Drain the brake fluid. Refer to “REMOVAL POINTS”. 1 Hose cover 1 2 Brake hose holder 1 3 Bolt (brake hose holder) 2 Only loosening. 4 Union bolt 2 5 Br ...

  • Yamaha YZ125N1 - page 171

    5-11 CHAS FRONT BRAKE AND REAR BRAKE EC5A8100 REAR BRAKE Extent of removal Order Part name Q’ty Remarks REAR BRAKE REMOVAL Preparation for Hold the machine by placing the removal suitable stand under the engine. Rear wheel Refer to “FRONT WHEEL AND REAR WHEEL” section. Drain the brake fluid. Refer to “REMOVAL POINTS”. 1 Pad pin pulg 1 Rem ...

  • Yamaha YZ125N1 - page 172

    5-12 CHAS FRONT BRAKE AND REAR BRAKE Extent of removal Order Part name Q’ty Remarks CALIPER DISASSEMBLY AB 1 Pad pin 1 1 2 Brake pad 2 2 3 Pad support 1 1 4 Caliper piston 2 1 Refer to “REMOVAL POINTS”. 5 Dust seal 2 1 Refer to “REMOVAL POINTS”. 6 Piston seal 2 1 EC5A8200 CALIPER DISASSEMBL Y A Front B Rear Extent of removal: 1 Front cali ...

  • Yamaha YZ125N1 - page 173

    5-13 CHAS FRONT BRAKE AND REAR BRAKE Extent of removal Order Part name Q’ty Remarks MASTER CYLINDER DISASSEMBLY 1 Master cylinder cap 1 2 Diaphragm 1 3 Master cylinder boot 1 4 Circlip 1 Use a long nose circlip pliers. 5 Plain washer 1 6 Push rod 1 7 Master cylinder kit 1 EC5A8300 MASTER CYLINDER DISASSEMBL Y A Front B Rear Extent of removal: 1 F ...

  • Yamaha YZ125N1 - page 174

    5-14 CHAS FRONT BRAKE AND REAR BRAKE EC5A3000 REMOV AL POINTS EC5A3100 Brake fluid 1. Remove: [Front] 9 Master cylinder cap 1 [Rear] 9 Reservoir tank cap 1 9 Protector NOTE: Do not remove the diaphragm. A Front B Rear 2. Connect the transparent hose 1 to the bleed screw 2 and place a suitable contain- er under its end. A Front B Rear 3. Loosen the ...

  • Yamaha YZ125N1 - page 175

    5-15 CHAS FRONT BRAKE AND REAR BRAKE EC533402 Piston seal kit 1. Remove: 9 Dust seal 1 9 Piston seal 2 NOTE: Remove the piston seals and dust seals by pushing them with a finger . c C Never attempt to pry out piston seals and dust seals. w Replace the piston seals and dust seals whenever a caliper is disassembled. A Front B Rear EC5A4000 INSPECTION ...

  • Yamaha YZ125N1 - page 176

    5-16 CHAS FRONT BRAKE AND REAR BRAKE EC534214 Caliper 1. Inspect: 9 Caliper cylinder inner surface a Wear/Score marks → Replace caliper as- sembly . A Front B Rear 2. Inspect: 9 Caliper piston 1 Wear/Score marks → Replace caliper piston assembly . w Replace the piston seals and dust seals 2 2 whenever a caliper is disassembled. EC534301 Brake h ...

  • Yamaha YZ125N1 - page 177

    5-17 CHAS FRONT BRAKE AND REAR BRAKE 2. Install: 9 Piston seal 1 9 Dust seal 2 w Always use new piston seals and dust seals. NOTE: Fit the piston seals and dust seals onto the slot on caliper correctly . A Front B Rear 3. Install: 9 Caliper piston 1 NOTE: Apply the brake fluid on the piston wall. c C 9 For the front caliper , install the piston wit ...

  • Yamaha YZ125N1 - page 178

    5-18 CHAS FRONT BRAKE AND REAR BRAKE 3. Install: 9 Brake hose holder 1 9 Caliper 2 9 Bolt (caliper) 3 NOTE: Fit the brake hose holder cut a over the projec- tion b on the front fork and clamp the brake hose. 4. T ighten: 9 Pad pin 4 5. Install: 9 Pad pin plug 5 EC5A5120 Rear caliper 1. Install: 9 Pad support 1 9 Brake pad 2 9 Pad pin 3 NOTE: 9 Inst ...

  • Yamaha YZ125N1 - page 179

    5-19 CHAS FRONT BRAKE AND REAR BRAKE 2. Install: 9 Disc cover 1 9 Bolt (disc cover) 2 3. Install: 9 Copper washer 1 9 Brake hose 2 9 Union bolt 3 w Always use new copper washers. c C Install the brake hose to the caliper with the paint a a on the pipe facing the caliper and with the pipe contacting the caliper projection b b . 7 Nm (0.7 m•kg, 5.1 ...

  • Yamaha YZ125N1 - page 180

    5-20 CHAS FRONT BRAKE AND REAR BRAKE EC5A5220 Master cylinder kit 1. Clean: 9 Master cylinder 9 Master cylinder kit Clean them with brake fluid. 2. Install: 9 Master cylinder cup (primary) 1 9 Master cylinder cup (secondary) 2 T o master cylinder piston 3 . NOTE: Apply the brake fluid on the master cylinder cup. w After installing, cylinder cup sho ...

  • Yamaha YZ125N1 - page 181

    5-21 CHAS FRONT BRAKE AND REAR BRAKE 4. Install: [Front] 9 Master cylinder kit 1 9 Plain washer 2 9 Circlip 3 9 Master cylinder boot 4 T o master cylinder 5 . [Rear] 9 Master cylinder kit 1 9 Push rod 2 9 Circlip 3 9 Master cylinder boot 4 T o master cylinder 5 . NOTE: 9 Apply the brake fluid on the master cylinder kit. 9 Apply the lithium soap bas ...

  • Yamaha YZ125N1 - page 182

    5-22 CHAS FRONT BRAKE AND REAR BRAKE 2. Install: 9 Master cylinder 1 9 Bolt (master cylinder) 2 EC5A5400 Rear master cylinder 1. Install: 9 Reservoir hose 1 9 Reservoir tank 2 NOTE: Pass the reservoir hose into the hose guide. 10 Nm (1.0 m•kg, 7.2 ft•lb) 26 Nm (2.6 m•kg, 19 ft•lb) 3. Install: 9 Spring 1 9 Brake pedal 2 9 O-ring 3 9 Bolt (br ...

  • Yamaha YZ125N1 - page 183

    5-23 CHAS FRONT BRAKE AND REAR BRAKE EC5A5911 Front brake hose 1. Install: 9 Brake hose 1 T o brake hose holder 2 . NOTE: Before tightening the bolt (brake hose holder), align the top a of the brake hose neck with the brake hose holder bottom b . Then pass the brake hose in front of the axle boss c and fit it into the hose groove d so that the brak ...

  • Yamaha YZ125N1 - page 184

    5-24 CHAS FRONT BRAKE AND REAR BRAKE EC5A5500 Rear brake hose 1. Install: 9 Copper washer 1 9 Brake hose 2 9 Union bolt 3 w Always use new copper washers. c C Install the brake hose so that its pipe por- tion a a directs as show and lightly touches the projection b b on the master cylinder . 30 Nm (3.0 m•kg, 22 ft•lb) 4. Install: 9 Copper washe ...

  • Yamaha YZ125N1 - page 185

    5-25 CHAS FRONT BRAKE AND REAR BRAKE 2. Install: 9 Brake hose holder 1 9 Screw (brake hose holder) 2 c C After installing the brake hose holders, make sure the brake hose does not contact the spring (rear shock absorber). If it does, correct its twist. EC5A5600 Brake fluid 1. Fill: 9 Brake fluid Until the fluid level reaches “LOWER” level line ...

  • Yamaha YZ125N1 - page 186

    5-26 CHAS FRONT BRAKE AND REAR BRAKE 2. Air bleed: 9 Brake system Refer to “BRAKE SYSTEM AIR BLEED- ING” section in the CHAPTER 3. 3. Inspect: 9 Brake fluid level Fluid at lower level → Fill up. Refer to “BRAKE FLUID LEVEL INSPEC- TION” section in the CHAPTER 3. 4. Install: [Front] 9 Diaphragm 9 Master cylinder cap 1 9 Screw (master cylin ...

  • Yamaha YZ125N1 - page 187

    5-27 CHAS FRONT FORK Extent of removal Order Part name Q’ty Remarks FRONT FORK REMOVAL Preparation for Hold the machine by placing the removal suitable stand under the engine. Front wheel Refer to “FRONT WHEEL AND REAR WHEEL”section. Front caliper Refer to “FRONT BRAKE AND REAR BRAKE”section. Number plate 1 Protector 1 2 Brake hose holder ...

  • Yamaha YZ125N1 - page 188

    5-28 CHAS FRONT FORK Extent of removal Order Part name Q’ty Remarks FRONT FORK DISASSEMBLY 1 Cap bolt 1 Refer to “REMOVAL POINTS”. 2 Fork spring 1 Drain the folk oil. 3 Dust seal 1 4 Stopper ring 1 Refer to “REMOVAL POINTS”. 5 Inner tube 1 6 Outer tube 1 7 Piston metal 1 8 Slide metal 1 9 Plain washer 1 0 Oil seal 1 q Spring guide 1 w Bas ...

  • Yamaha YZ125N1 - page 189

    5-29 CHAS FRONT FORK EC556000 HANDLING NOTE NOTE: The front fork requires careful attention. So it is recommended that the front fork be maintained at the dealers. c C T o prevent an accidental explosion of air , the following instructions should be ob- served: 9 The front fork with a built-in piston rod has a very sophisticated internal con- struc ...

  • Yamaha YZ125N1 - page 190

    5-30 CHAS FRONT FORK EC553201 Inner tube 1. Remove: 9 Dust seal 1 9 Stopper ring 2 Using slotted-head screwdriver . c C T ake care not to scratch the inner tube. 2. Remove: 9 Inner tube 1 EC553311 Damper rod 1. Remove: 9 Base valve 1 9 Damper rod 2 NOTE: Use a damper rod holder 3 to lock the damper rod. EC554000 INSPECTION EC554100 Damper rod 1. In ...

  • Yamaha YZ125N1 - page 191

    5-31 CHAS FRONT FORK EC554200 Base valve 1. Inspect: 9 V alve assembly 1 Wear/Damage → Replace. 9 O-ring 2 Damage → Replace. EC554400 Fork spring 1. Measure: 9 Fork spring free length a Out of specification → Replace. EC554502 Inner tube 1. Inspect: 9 Inner tube surface a Score marks → Repair or replace. Use #1,000 grit wet sandpaper . Dama ...

  • Yamaha YZ125N1 - page 192

    5-32 CHAS FRONT FORK EC554700 Cap bolt 1. Inspect: 9 Cap bolt 1 9 O-ring 2 9 Air bleed screw 3 Wear/Damage → Replace. EC555000 ASSEMBL Y AND INST ALLA TION EC5551A1 Front fork assembly 1. W ash the all parts in a clean solvent. 2. Install: 9 Damper rod 1 T o inner tube 2 . c C T o install the damper rod into the inner tube, hold the inner tube as ...

  • Yamaha YZ125N1 - page 193

    5-33 CHAS FRONT FORK 5. Install: 9 Spring guide 1 9 Locknut 2 T o damper rod 3 . NOTE: 9 Install the spring guide with its cut a facing up- ward. 9 With its thread b facing upward, fully finger tighten the locknut onto the damper rod. 6. Install: 9 Dust seal 1 9 Stopper ring 2 9 Oil seal 3 9 Plain washer 4 9 Slide metal 5 T o inner tube 6 . NOTE: 9 ...

  • Yamaha YZ125N1 - page 194

    5-34 CHAS FRONT FORK 9. Install: 9 Slide metal 1 9 Plain washer 2 T o outer tube slot. NOTE: Press the slide metal into the outer tube with fork seal driver 3 . 10. Install: 9 Oil seal 1 NOTE: Press the oil seal into the outer tube with fork seal driver 2 . 1 1. Install: 9 Stopper ring 1 NOTE: Fit the stopper ring correctly in the groove in the out ...

  • Yamaha YZ125N1 - page 195

    5-35 CHAS FRONT FORK 13. Check: 9 Inner tube smooth movement T ightness/Binding/Rough spots → Repeat the steps 2 to 12. 14. Compress the front fork fully . 15. Fill: 9 Front fork oil Until outer tube top surface with recom- mended fork oil 1 . c C 9 Be sure to use recommended fork oil. If other oils are used, they may have an ex- cessively advers ...

  • Yamaha YZ125N1 - page 196

    5-36 CHAS FRONT FORK 19. W ait ten minutes until the air bubbles have been removed from the front fork, and the oil has dispense evenly in system before setting recommended oil level. NOTE: Fill with the fork oil up to the top end of the outer tube, or the fork oil will not spread over to every part of the front forks, thus making it impossible to ...

  • Yamaha YZ125N1 - page 197

    5-37 CHAS FRONT FORK 23. Install: 9 Cushion rubber 1 9 W asher 2 9 Spacer 3 T o cap bolt 4 . NOTE: Install the cushion rubber with its smaller dia.end a facing the cap bolt. 21. Measure: 9 Distance a Out of specification → T urn into the locknut. 24. Install: 9 Push rod 1 9 Fork spring 2 NOTE: 9 Install the fork spring with the damper rod 3 pulle ...

  • Yamaha YZ125N1 - page 198

    5-38 CHAS FRONT FORK 2. T ighten: 9 Cap bolt 1 3. Adjust: 9 Front fork top end a 30 Nm (3.0 m•kg, 22 ft•lb) Front fork top end (standard) a a : 5 mm (0.20 in) 26. T ighten: 9 Cap bolt (locknut) 1 NOTE: 9 While compressing the fork spring, set the thin type spanners 2 between the spacer 3 and spring guide 4 . 9 Hold the locknut 5 and tighten the ...

  • Yamaha YZ125N1 - page 199

    5-39 CHAS FRONT FORK 7. Adjust: 9 Rebound damping force NOTE: T urn in the damping adjuster 1 finger-tight and then turn out to the originally set position. 4. T ighten: 9 Pinch bolt (handle crown) 1 9 Pinch bolt (under bracket) 2 c C Tighten the under bracket to specified torque. If torqued too much, it may cause the front fork to malfunction. 5. ...

  • Yamaha YZ125N1 - page 200

    5-40 CHAS HANDLEBAR Extent of removal Order Part name Q’ty Remarks Preparation for HANDLEBAR REMOVAL removal Number plate Remove the clamp portion only. 1 Clutch cable 1 Disconnect at the lever side. 2 Clutch lever holder 1 3 “ENGINE STOP” button 1 4 Master cylinder 1 Refer to “REMOVAL POINTS”. 5 Throttle cable cap 1 Turn over the cap cov ...

  • Yamaha YZ125N1 - page 201

    5-41 CHAS HANDLEBAR Extent of removal: 1 Throttle disassembly Extent of removal Order Part name Q’ty Remarks THROTTLE DISASSEMBLY 1 Grip cap (lower) 1 2 Grip cap (upper) 1 3 Grip assembly 1 4 Grip (right) 1 Refer to “REMOVAL POINTS”. 5 Tube guide 1 1 EC5B8000 THROTTLE DISASSEMBL Y 4 Nm (0.4 m•kg, 2.9 ft•lb) 5MV-9-10-5B 6/13/00 3:17 PM Pag ...

  • Yamaha YZ125N1 - page 202

    5-42 CHAS HANDLEBAR EC5B3000 REMOV AL POINTS EC5B3100 Master cylinder 1. Remove: 9 Master cylinder bracket 1 9 Master cylinder 2 c C 9 Do not let the master cylinder hang on the brake hose. 9 Keep the master cylinder cap side horizontal to prevent air from coming in. EC5B3200 Grip 1. Remove: 9 Grip 1 NOTE: Blow in air between the handlebar or tube ...

  • Yamaha YZ125N1 - page 203

    5-43 CHAS HANDLEBAR 2. Install: 9 Grip cap (upper) 1 9 Grip cap (lower) 2 9 Bolt (grip cap) 3 NOTE: T emporarily tighten the bolts (grip cap). EC5B5210 Handlebar 1. Install: 9 Handlebar 1 9 Handlebar holder 2 9 Bolt (handlebar holder) 3 NOTE: 9 The upper handlebar holder should be installed with the punched mark a forward. 9 First tighten the bolts ...

  • Yamaha YZ125N1 - page 204

    5-44 CHAS HANDLEBAR 4. Install: 9 Throttle cable 1 T o tube guide 2 . NOTE: Apply the lithium soap base grease on the throt- tle cable end and tube guide cable winding por- tion. 5. Install: 9 Roller 1 9 Collar 2 NOTE: 9 Apply the lithium soap base grease on the roller sliding surface. 9 Install the roller so that the “UPPER” mark a faces upwar ...

  • Yamaha YZ125N1 - page 205

    5-45 CHAS HANDLEBAR 10. Install: 9 Bolt (grip cap) 1 w 9 Install the grip cap so that the gaps a a and b b between the bolt (grip cap) and brake lever 2 2 are equal. If you make a mistake in the grip cap installation position, the brake lever may contact the grip cap, resulting in poor brake performance. 9 After tightening the bolts, check that the ...

  • Yamaha YZ125N1 - page 206

    5-46 CHAS HANDLEBAR 14. Clamp the clamp portion a of the number plate to the handlebar . 15. Insert the end of the fuel breather hose 1 into the hole of the number plate. 5MV-9-10-5C 6/12/00 8:51 PM Page 5-46 ...

  • Yamaha YZ125N1 - page 207

    5-47 CHAS STEERING Extent of removal Order Part name Q’ty Remarks STEERING REMOVAL Preparation for Hold the machine by placing the removal suitable stand under the engine. Number plate Handlebar Refer to “HANDLEBAR” section. Cable guide Front fender 1 Steering shaft nut 1 2 Front fork 2 Refer to “FRONT FORK” section. 3 Handle crown 1 4 Ri ...

  • Yamaha YZ125N1 - page 208

    5-48 CHAS STEERING EC563000 REMOV AL POINTS EC563202 Ring nut 1. Remove: 9 Ring nut 1 Use the ring nut wrench 2 . w Support the steering shaft so that it may not fall down. EC563300 Bearing (lower) 1. Remove: 9 Bearing (lower) 1 Use the floor chisel 2 . c C T ake care not to damage the steering shaft thread. EC563400 Ball race 1. Remove: 9 Ball rac ...

  • Yamaha YZ125N1 - page 209

    5-49 CHAS STEERING EC564101 Bearing and ball race 1. W ash the bearings and ball races with a sol- vent. 2. Inspect: 9 Bearing 1 9 Ball race Pitting/Damage → Replace bearings and ball races as a set. Install the bearing in the ball races. Spin the bearings by hand. If the bearings hang up or are not smooth in their operation in the ball races, re ...

  • Yamaha YZ125N1 - page 210

    5-50 CHAS STEERING 4. Install: 9 Plain washer 1 9 Ring nut 2 T ighten the ring nut using the ring nut wrench 3 . Refer to “STEERING HEAD INSPECTION AND ADJUSTMENT” section in the CHAP- TER 3. 5. Check the steering shaft by turning it lock to lock. If there is any binding, remove the steering shaft assembly and inspect the steering bearings. 6. ...

  • Yamaha YZ125N1 - page 211

    5-51 CHAS STEERING 9. After tightening the nut, check the steering for smooth movement. If not, adjust the steering by loosening the ring nut little by little. 10. Adjust: 9 Front fork top end a 1 1. T ighten: 9 Pinch bolt (handle crown) 1 9 Pinch bolt (under bracket) 2 c C Tighten the under bracket to specified torque. If torqued too much, it may ...

  • Yamaha YZ125N1 - page 212

    5-52 CHAS SWINGARM Extent of removal Order Part name Q’ty Remarks SWINGARM REMOVAL Preparation for Hold the machine by placing the removal suitable stand under the engine. Brake hose holder Refer to “FRONT BRAKE AND Rear caliper REAR BRAKE”section. Bolt (brake pedal) Shift the brake pedal backward. Drive chain 1 Chain support 1 2 Chain tensio ...

  • Yamaha YZ125N1 - page 213

    5-53 CHAS SWINGARM Extent of removal Order Part name Q’ty Remarks SWINGARM DISASSEMBLY 1 Cap 2 2 Relay arm 1 3 Connecting rod 1 4 Collar 2 5 Oil seal 2 6 Thrust bearing 2 7 Bush 2 8 Oil seal 8 9 Bearing 8 Refer to “REMOVAL POINTS”. EC578000 SWINGARM DISASSEMBL Y Extent of removal: 1 Swingarm disassembly 2 Connecting rod removal and disassembl ...

  • Yamaha YZ125N1 - page 214

    5-54 CHAS SWINGARM EC573000 REMOV AL POINTS EC573200 Bearing 1. Remove: 9 Bearing 1 NOTE: Install the bearing by pressing its outer race. EC574010 INSPECTION W ash the bearings, bushes, collars, and covers in a solvent. EC574111 Swingarm 1. Inspect: 9 Bearing 1 9 Bush 2 Free play exists/Unsmooth revolution/Rust → Replace bearing and bush as a set ...

  • Yamaha YZ125N1 - page 215

    5-55 CHAS SWINGARM EC575000 ASSEMBL Y AND INST ALLA TION EC575202 Bearing and oil seal 1. Install: 9 Bearing 1 9 Oil seal 2 T o swingarm. NOTE: 9 Apply the molybdenum disulfide grease on the bearing when installing. 9 Install the bearing by pressing it on the side hav- ing the manufacture's marks or numbers. 9 First install the outer and then ...

  • Yamaha YZ125N1 - page 216

    5-56 CHAS SWINGARM EC5751B1 Swingarm 1. Install: 9 Bush 1 9 Thrust bearing 2 9 Oil seal 3 9 Collar 4 T o swingarm 5 . NOTE: Apply the molybdenum disulfide grease on the bushes, thrust bearings and oil seal lips. 2. Install: 9 Collar 1 T o relay arm 2 . NOTE: Apply the molybdenum disulfide grease on the collars, bearings and oil seal lips. 3. Instal ...

  • Yamaha YZ125N1 - page 217

    5-57 CHAS SWINGARM 5. Install: 9 Relay arm 1 9 Bolt (relay arm) 2 9 Plain washer 3 9 Nut (relay arm) 4 T o swingarm. NOTE: 9 Apply the molybdenum disulfide grease on the bolt. 9 Do not tighten the nut yet. 6. Install: 9 Swingarm 1 9 Pivot shaft 2 NOTE: 9 Apply the molybdenum disulfide grease on the pivot shaft. 9 Insert the pivot shaft from right s ...

  • Yamaha YZ125N1 - page 218

    5-58 CHAS SWINGARM 10. T ighten: 9 Nut (connecting rod) 1 1 1. T ighten: 9 Nut (relay arm) 1 12. Install: 9 Cap 1 NOTE: Install the cap with its mark a facing forward. 13. Install: 9 Bolt [chain tensioner (lower)] 1 9 Plain washer 2 9 Collar 3 9 Chain tensioner 4 9 Nut [chain tensioner (lower)] 5 14. Install: 9 Chain support 1 9 Support cover 2 9 B ...

  • Yamaha YZ125N1 - page 219

    5-59 CHAS REAR SHOCK ABSORBER Extent of removal Order Part name Q’ty Remarks REAR SHOCK ABSORBER REMOVAL Preparation for Hold the machine by placing the removal suitable stand under the engine. Seat Refer to “SEAT, FUEL TANK AND SIDE COVERS” section. Silencer Refer to “EXHAUST PIPE AND SILENCER” section. 1 Clamp (air cleaner joint) 1 Loos ...

  • Yamaha YZ125N1 - page 220

    5-60 CHAS REAR SHOCK ABSORBER EC586000 HANDLING NOTE w This shock absorber is provided with a separate type tank filled with high-pressure nitrogen gas. T o prevent the danger of ex- plosion, read and understand the following information before handling the shock ab- sorber . The manufacturer can not be held respon- sible for property damage or per ...

  • Yamaha YZ125N1 - page 221

    5-61 CHAS REAR SHOCK ABSORBER EC583000 REMOV AL POINTS EC583320 Bearing 1. Remove: 9 Stopper ring (upper bearing) 1 NOTE: Press in the bearing while pressing its outer race and remove the stopper ring. 2. Remove: 9 Upper bearing 1 NOTE: Remove the bearing by pressing its outer race. EC584000 INSPECTION EC584110 Rear shock absorber 1. Inspect: 9 Dam ...

  • Yamaha YZ125N1 - page 222

    5-62 CHAS REAR SHOCK ABSORBER EC585111 Spring (rear shock absorber) 1. Install: 9 Spring 1 9 Spring guide (upper) 2 9 Spring guide (lower) 3 2. T ighten: 9 Adjuster 1 EC585000 ASSEMBL Y AND INST ALLA TION EC585320 Bearing 1. Install: 9 Upper Bearing 1 NOTE: Install the bearing parallel until the stopper ring groove appears by pressing its outer rac ...

  • Yamaha YZ125N1 - page 223

    5-63 CHAS REAR SHOCK ABSORBER 3. Adjust: 9 Spring length (installed) a *For EUROPE NOTE: The length of the spring (installed) changes 1.5 mm (0.06 in) per turn of the adjuster . c C Never attempt to turn the adjuster beyond the maximum or minimum setting. 4. T ighten: 9 Locknut 1 Spring length (installed) a a : Standard length 248 mm (9.76 in) *262 ...

  • Yamaha YZ125N1 - page 224

    5-64 CHAS REAR SHOCK ABSORBER 3. Install: 9 Rear shock absorber 4. Install: 9 Bolt (rear shock absorber-frame) 1 9 Nut (rear shock absorber-frame) 2 NOTE: Apply the molybdenum disulfide grease on the bolt. 5. Install: 9 Plain washer 1 9 Bolt (rear shock absorber-relay arm) 2 NOTE: 9 Apply the molybdenum disulfide grease on the bolt. 9 Insert the bo ...

  • Yamaha YZ125N1 - page 225

    6-1 ELEC ELECTRICAL COMPONENTS AND WIRING DIAGRAM 6 EC600000 ELECTRICAL EC610000 ELECTRICAL COMPONENTS AND WIRING DIAGRAM EC611000 ELECTRICAL COMPONENTS 1 “ENGINE STOP” button 2 Ignition coil 3 CDI unit 4 CDI magneto 5 Spark plug EC612000 WIRING DIAGRAM COLOR CODE B...................Black O ..................Orange B/R ...............Brack/Red ...

  • Yamaha YZ125N1 - page 226

    6-2 ELEC IGNITION SYSTEM 6 EC620000 IGNITION SYSTEM EC621002 INSPECTION STEPS Use the following steps for checking the possibility of the malfunctioning engine being attributable to ignition system failure and for checking the spark plug which will not spark. *Clean or replace spark plug. Primary coil Secondary coil Repair or replace. Spark Check e ...

  • Yamaha YZ125N1 - page 227

    6-3 ELEC IGNITION SYSTEM EC622001 SP ARK GAP TEST 1. Disconnect the spark plug cap from spark plug. 2. Connect the dynamic spark tester 1 (igni- tion checker 2 ) as shown. 9 Spark plug cap 3 9 Spark plug 4 A For USA and CDN B Except for USA and CDN 3. Kick the kick starter . 4. Check the ignition spark gap. 5. Start engine, and increase spark gap u ...

  • Yamaha YZ125N1 - page 228

    6-4 ELEC IGNITION SYSTEM EC626002 IGNITION COIL INSPECTION 1. Inspect: 9 Primary coil resistance Out of specification → Replace. 2. Inspect: 9 Secondary coil resistance Out of specification → Replace. NOTE: When inspecting the secondary coil resistance, remove the spark plug cap. T ester (+) lead → Orange lead 1 T ester (–) lead → Black l ...

  • Yamaha YZ125N1 - page 229

    6-5 ELEC IGNITION SYSTEM EC627011 CDI MAGNETO INSPECTION 1. Inspect: 9 Pick-up coil resistance Out of specification → Replace. 2. Inspect: 9 Source coil 1 resistance Out of specification → Replace. 3. Inspect: 9 Source coil 2 resistance Out of specification → Replace. EC628000 CDI UNIT INSPECTION Check all electrical components. If no fault i ...

  • Yamaha YZ125N1 - page 230

    7-1 TUN SETTING 7 EC700000 TUNING EC710000 ENGINE EC711001 Carburetor setting 9 The role of fuel is to cool the engine, and in the case of a 2-stroke engine, to lubricate the engine in addition to power generation. Accordingly , if a mixture of air and fuel is too lean, abnormal combustion will occur , and engine seizure may result. If the mixture ...

  • Yamaha YZ125N1 - page 231

    7-2 TUN SETTING That is: 9 Higher temperature expands the air with its resultant reduced density . 9 Higher humidity reduces the amount of oxygen in the air by so much of the water vapor in the same air . 9 Lower atmospheric pressure (at a high altitude) reduces the density of the air . EC713001 T est run After warming up the engine equipped with t ...

  • Yamaha YZ125N1 - page 232

    7-3 TUN SETTING EC714060 Effect of setting parts in relation to throttle valve opening 1 Throttle valve opening 2 Full-open 3 Full-closed EC715002 Main jet adjustment The richness of air-fuel mixture with 1/2~4/4 throttle can be set by changing the main jet 1 . 1. Spark plug is too hot. Select a main jet having higher calibrating No. than standard. ...

  • Yamaha YZ125N1 - page 233

    7-4 TUN SETTING EC716001 Pilot air screw adjustment The richness of air-fuel mixture with full closed to 1/4 throttle can be set by turning the pilot air screw 1 . T urning in the pilot air screw will enrich the mix- ture at low speeds, and turning out it will lean out the mixture. EC71R000 Pilot jet adjustment The air-fuel mixture can basically be ...

  • Yamaha YZ125N1 - page 234

    7-5 TUN SETTING EC718010 Jet needle groove position adjustment Should the engine be hard to run smoothly at intermediate speeds, the jet needle 1 must be adjusted. If the mixture is too rich or too lean at intermediate speed operation, irregular engine operation and poor acceleration will result. Whether or not the richness of the mixture is proper ...

  • Yamaha YZ125N1 - page 235

    7-6 TUN SETTING EC719071 Jet needle adjustment (For USA, CDN, ZA, AUS and NZ) On the carburetors used in the YZ125, the main nozzle is a non disassembly type, so it can not be replaced. Therefore, carburetor setting requires the change of the jet needle. 1. The jet needle setting parts, having the same taper angle, are available in different straig ...

  • Yamaha YZ125N1 - page 236

    7-7 TUN SETTING EC719071 Jet needle adjustment (For EUROPE) On the carburetors used in the YZ125, the main nozzle is a non disassembly type, so it can not be replaced. Therefore, carburetor setting requires the change of the jet needle. 1. The jet needle setting parts, having the same taper angle, are available in different straight portion diamete ...

  • Yamaha YZ125N1 - page 237

    TUN 7-8 SETTING EC71B040 Relationship with throttle opening The flow of the fuel through the carburetor main system is controlled by the main jet and then, it is further regulated by the area between the main nozzle and the jet needle. On the relationship between the fuel flow and the throttle opening, the fuel flow relates to the straight portion ...

  • Yamaha YZ125N1 - page 238

    TUN 7-9 SETTING EC71Q000 Carburetor setting parts Part name Size Part number Main jet 1 1 Lean #420 137-14143-84 #430 137-14143-86 #440 137-14143-88 *(STD) #450 137-14143-90 (STD) #460 137-14143-92 #470 137-14143-94 #480 137-14143-96 Rich #490 137-14143-98 Pilot jet 2 2 Lean #20 4KM-14142-20 #22.5 4KM-14142-22 (STD) #25 4KM-14142-25 #27.5 4KM-14142 ...

  • Yamaha YZ125N1 - page 239

    TUN 7-10 SETTING EC71C020 Road condition and examples of carburetor setting EC71D040 Examples of carburetor setting depending on symptom Symptom Setting Checking At full throttle Increase main jet calibration No. Discoloration of spark plug → Stall at high speeds (Gradually) If tan color, it is in good condition. * Hard breathing If can not be no ...

  • Yamaha YZ125N1 - page 240

    TUN 7-11 SETTING Symptom Setting Checking 0~1/4 throttle Use jet needle having a smaller Number of turns-back → * Hard breathing diameter. Correct properly Speed down Overflow from carburetor 0~1/4 throttle Use jet needle having a larger Poor acceleration diameter. White smoke Unstable at low speeds Lower jet needle clip position. Pinking noise ( ...

  • Yamaha YZ125N1 - page 241

    TUN 7-12 SETTING EC71M001 Change of the heat range of spark plugs Judging from the discoloration of spark plugs, if they are found improper , it can be corrected by the following two methods; changing carburetor settings and changing the heat range of spark plug. 9 In principle, it is advisable to first use spark plugs of standard heat range, and j ...

  • Yamaha YZ125N1 - page 242

    TUN 7-13 SETTING EC720000 CHASSIS EC71P002 Selection of the secondary reduction ratio (Sprocket) Secondary Number of driven sprocket teeth reduction = —————————————— ratio Number of drive sprocket teeth <Requirement for selection of secondary gear reduction ratio> 9 It is generally said that the secondary gear rati ...

  • Yamaha YZ125N1 - page 243

    TUN 7-14 SETTING EC72N000 Drive and driven sprockets setting parts EC721002 T ire pressure T ire pressure should be adjust to suit the road surface condition of the circuit. 9 Under a rainy , muddy , sandy , or slippery condi- tion, the tire pressure should be lower for a larg- er area of contact with the road surface. 9 Under a stony or hard road ...

  • Yamaha YZ125N1 - page 244

    TUN 7-15 SETTING EC722011 Front fork setting The front fork setting should be made depending on the rider ’s feeling of an actual run and the cir- cuit conditions. The front fork setting includes the following three factors: 1. Setting of air spring characteristics 9 Change the fork oil level. 2. Setting of spring preload 9 Change the spring. 9 I ...

  • Yamaha YZ125N1 - page 245

    TUN 7-16 SETTING EC727021 Spring preload adjustment The spring preload is adjusted by installing the adjustment washer 1 between the fork spring 2 and damper rod 3 . c C Do not install three or more adjustment washers for each front fork. w Always adjust each front fork to the same setting. Uneven adjustment can cause poor handling and loss of stab ...

  • Yamaha YZ125N1 - page 246

    TUN 7-17 SETTING 2. Use of stiff spring Generally a stiff spring gives a stif f riding feeling. Rebound damping tends to become weaker , resulting in lack of a sense of con- tact with the road surface or in a vibrating handlebar . T o set a stiff spring: 9 Change the rebound damping. T urn in one or two clicks. 9 Change the compression damping. T u ...

  • Yamaha YZ125N1 - page 247

    TUN 7-18 SETTING EC72P010 Front fork setting parts 9 Adjustment washer 1 9 Front fork spring 2 [Equal pitch spring ] [Unequal pitch spring ] NOTE: 9 The unequal pitch spring is softer in initial char- acteristic than the equal pitch spring and is diffi- cult to bottom out under full compression. 9 The I.D. mark (slits) a is proved on the end of the ...

  • Yamaha YZ125N1 - page 248

    TUN 7-19 SETTING EC72B000 Rear suspension setting The rear suspension setting should be made depending on the rider ’s feeling of an actual run and the circuit conditions. The rear suspension setting includes the follow- ing two factors: 1. Setting of spring preload 9 Change the set length of the spring. 9 Change the spring. 2. Setting of damping ...

  • Yamaha YZ125N1 - page 249

    TUN 7-20 SETTING NOTE: 9 If the machine is new and after it is broken in, the same set length of the spring may change because of the initial fatigue, etc. of the spring. Therefore, be sure to make re-evaluation. 9 If the standard figure cannot be achieved by adjusting the spring adjuster and changing the spring set length, replace the spring with ...

  • Yamaha YZ125N1 - page 250

    TUN 7-21 SETTING c C When using a rear cushion other than cur- rently installed, use the one whose overall length a a does not exceed the standard as it may result in faulty performance. Never use one whose overall length is greater than standard. å Coverage of spring by weight ∫ Rider weight 1 Soft 2 Standard 3 Stiff Length a a of standard shoc ...

  • Yamaha YZ125N1 - page 251

    TUN 7-22 SETTING EC72Q011 Rear shock absorber setting parts 9 Rear shock spring 1 [Equal pitch spring ] [Unequal pitch spring ] NOTE: 9 The unequal pitch spring is softer in initial char- acteristic than the equal pitch spring and is diffi- cult to bottom out under full compression. 9 The I.D. color a is marked at the end of the spring. 9 Extent of ...

  • Yamaha YZ125N1 - page 252

    TUN 7-23 SETTING EC72H010 Suspension setting 9 Front fork NOTE: 9 If any of the following symptoms is experienced with the standard position as the base, make reset- ting by reference to the adjustment procedure given in the same chart. 9 Before any change, set the rear shock absorber sunken length to the standard figure 90~100 mm (3.5~3.9 in). Sec ...

  • Yamaha YZ125N1 - page 253

    TUN 7-24 SETTING 9 Rear shock absorber NOTE: 9 If any of the following symptoms is experienced with the standard position as the base, make reset- ting by reference to the adjustment procedure given in the same chart. 9 Adjust the rebound damping in 2-click increments or decrements. 9 Adjust the low compression damping in 1-click increments or decr ...

  • Yamaha YZ125N1 - page 254

    PRINTED IN JAPAN 2000.6 | 2.9 ´ 1 iE j YZ125N1 PRINTED ON RECYCLED PAPER Y AMAHA MOT OR CO. , L TD. 2500 SHINGAI IW A T A SHIZUOKA JAP AN PROTECT YOUR INVESTMENT Use Genuine YAMAHA Parts And Accessories 5MV-10 00.6.13 0:53 PM y[W 1 (1,1) ...

Manufacturer Yamaha Category Motorcycle

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All of them are important, but the most important information from the point of view of use of the device are in the user manual Yamaha YZ125N1.

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