Yamaha YZF-R125 Service Manual
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Yamaha YZF-R125 Service Manual

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SERVICE MANUAL
YZF-R125
5D7-F8197-E0

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  • Page 1 YAMAHAR125.COM SERVICE MANUAL YZF-R125 5D7-F8197-E0...
  • Page 2 YamahaR125.COM For more information about Yamaha R125 http://www.yamahar125.com Login to EAS20060 YZF-R125 SERVICE MANUAL © by MBK Industrie First edition, January 2008 All rights reserved. Any reproduction or unauthorized use without the written permission of MBK Industrie is expressly prohibited.
  • Page 3 It is not possible to include all the knowledge of a mechanic in one manual. Therefore, any- one who uses this book to perform maintenance and repairs on Yamaha vehicles should have a basic understanding of mechanics and the techniques to repair these types of vehicles. Repair and mainte- nance work attempted by anyone without this knowledge is likely to render the vehicle unsafe and unfit for use.

  • Page 4: How To Use This Manual

    YamahaR125.COM EAS20090 HOW TO USE THIS MANUAL This manual is intended as a handy, easy-to-read reference book for the mechanic. Comprehensive explanations of all installation, removal, disassembly, assembly, repair and check procedures are laid out with the individual steps in sequential order. •...

  • Page 5: Symbols

    YamahaR125.COM EAS20100 1. Serviceable with engine mounted SYMBOLS 2. Filling fluid The following symbols are used in this manual 3. Lubricant for easier understanding. 4. Special tool NOTE: 5. Tightening torque The following symbols are not relevant to every 6. Wear limit, clearance vehicle.
  • Page 6 YamahaR125.COM...

  • Page 7: Table Of Contents

    YamahaR125.COM EAS20110 TABLE OF CONTENTS GENERAL INFORMATION SPECIFICATIONS PERIODIC CHECKS AND ADJUSTMENTS CHASSIS ENGINE COOLING SYSTEM FUEL SYSTEM ELECTRICAL SYSTEM TROUBLESHOOTING...
  • Page 8 YamahaR125.COM...

  • Page 9: General Information

    YamahaR125.COM GENERAL INFORMATION IDENTIFICATION .................... 1-1 VEHICLE IDENTIFICATION NUMBER ............. 1-1 MODEL LABEL..................1-1 FEATURES...................... 1-2 OUTLINE OF THE FI SYSTEM..............1-2 FI SYSTEM....................1-3 MULTI-FUNCTION DISPLAY..............1-4 IMPORTANT INFORMATION ................. 1-5 PREPARATION FOR REMOVAL AND DISASSEMBLY......1-5 REPLACEMENT PARTS................1-5 GASKETS, OIL SEALS AND O-RINGS ............

  • Page 10: Identification

    IDENTIFICATION YamahaR125.COM EAS20130 IDENTIFICATION EAS20140 VEHICLE IDENTIFICATION NUMBER The vehicle identification number “1” is stamped into the right side of the steering head pipe. EAS20150 MODEL LABEL The model label “1” is affixed to the frame. This information will be needed to order spare parts.

  • Page 11: Features

    FEATURES YamahaR125.COM EAS20170 FEATURES EAS5D71022 OUTLINE OF THE FI SYSTEM The main function of a fuel supply system is to provide fuel to the combustion chamber at the optimum air-fuel ratio in accordance with the engine operating conditions and the atmospheric temperature. In the conventional carburetor system, the air-fuel ratio of the mixture that is supplied to the combustion chamber is created by the volume of the intake air and the fuel that is metered by the jet used in the respective carburetor.

  • Page 12: Fi System

    FEATURES YamahaR125.COM EAS5D71023 FI SYSTEM The fuel pump delivers fuel to the fuel injector via the fuel filter. The pressure regulator maintains the fuel pressure that is applied to the fuel injector at only 250 kPa (2.50 kg/cm², 36.3 psi). Accordingly, when the energizing signal from the ECU energizes the fuel injector, the fuel passage opens, causing the fuel to be injected into the intake manifold only during the time the passage remains open.

  • Page 13: Multi-Function Display

    FEATURES YamahaR125.COM To reset a tripmeter, select it by pushing the EAS5D71046 MULTI-FUNCTION DISPLAY “RESET/SELECT” button briefly (less than one second), and then push the button for at least three seconds while the selected tripmeter is flashing. If you do not reset the fuel reserve trip- meter manually, it will reset itself automatically and the display will return to the prior mode after refueling and traveling 5 km (3 mi).

  • Page 14: Important Information

    5. Keep all parts away from any source of fire. EAS20200 REPLACEMENT PARTS Use only genuine Yamaha parts for all replace- ments. Use oil and grease recommended by Yamaha for all lubrication jobs. Other brands may be similar in function and appearance, but...

  • Page 15: Bearings And Oil Seals

    IMPORTANT INFORMATION YamahaR125.COM EAS20230 BEARINGS AND OIL SEALS Install bearings “1” and oil seals “2” so that the manufacturer’s marks or numbers are visible. When installing oil seals “1”, lubricate the oil seal lips with a light coat of lithium-soap-based grease.

  • Page 16: Checking The Connections

    CHECKING THE CONNECTIONS YamahaR125.COM EAS20250 CHECKING THE CONNECTIONS Pocket tester 90890-03112 Check the leads, couplers, and connectors for Analog pocket tester stains, rust, moisture, etc. YU-03112-C 1. Disconnect: • Lead NOTE: • Coupler • If there is no continuity, clean the terminals. •...
  • Page 17 SPECIAL TOOLS YamahaR125.COM EAS20260 SPECIAL TOOLS The following special tools are necessary for complete and accurate tune-up and assembly. Use only the appropriate special tools as this will help prevent damage caused by the use of inappropriate tools or improvised techniques. Special tools, part numbers or both may differ depending on the country. When placing an order, refer to the list provided below to avoid any mistakes.
  • Page 18 90890-01326 T-handle 3/8" drive 60 cm long YM-01326 Fork seal driver weight 4-49, 4-50 90890-01367 Replacement hammer YM-A9409-7 Fork seal driver attachment (ø33) 4-49 90890-01368 Replacement 33 mm YM-A9409-4 Yamaha bond No. 1215 5-12, 5-33, 90890-85505 5-60 (Three Bond No.1215®)
  • Page 19 SPECIAL TOOLS YamahaR125.COM Reference Tool name/Tool No. Illustration pages Valve spring compressor 5-18, 5-23 90890-04019 YM-04019 Valve spring compressor attachment 5-18, 5-23 90890-04108 Valve spring compressor adapter 22 mm YM-04108 Valve guide remover (ø4.5) 5-19 90890-04116 Valve guide remover (4.5 mm) YM-04116 Valve guide installer (ø4.5) 5-19...

  • Page 20: Special Tools

    SPECIAL TOOLS YamahaR125.COM Reference Tool name/Tool No. Illustration pages Universal clutch holder 5-42, 5-44 90890-04086 YM-91042 Thickness gauge 5-42 90890-03180 Feeler gauge set YU-26900-9 Crankcase separating tool 5-62 90890-01135 Crankcase separator YU-01135-B Crankshaft installer pot 5-63 90890-01274 Installing pot YU-90058 YU-90058/YU-90059 Crankshaft installer bolt 5-63...
  • Page 21 SPECIAL TOOLS YamahaR125.COM Reference Tool name/Tool No. Illustration pages Adapter (M12) 5-63 90890-01278 Adapter #3 YU-90063 Spacer (crankshaft installer) 5-63 90890-04081 Pot spacer YM-91044 YM-91044 Radiator cap tester 90890-01325 Radiator pressure tester YU-24460-01 YU-24460-01 Radiator cap tester adapter 90890-01352 Radiator pressure tester adapter YU-33984 YU-33984 Mechanical seal installer...
  • Page 22 SPECIAL TOOLS YamahaR125.COM Reference Tool name/Tool No. Illustration pages Middle driven shaft bearing driver 90890-04058 Bearing driver 40 mm YM-04058 Pressure gauge 90890-03153 YU-03153 Fuel pressure adapter 90890-03181 Ignition checker 8-69 90890-06754 Opama pet-4000 spark checker YM-34487 Digital circuit tester 8-73 90890-03174 Model 88 Multimeter with tachometer...

  • Page 23: Specifications

    YamahaR125.COM SPECIFICATIONS GENERAL SPECIFICATIONS ................ 2-1 ENGINE SPECIFICATIONS ................2-2 CHASSIS SPECIFICATIONS ................2-9 ELECTRICAL SPECIFICATIONS ..............2-12 TIGHTENING TORQUES ................2-15 GENERAL TIGHTENING TORQUE SPECIFICATIONS......2-15 ENGINE TIGHTENING TORQUES............2-16 CHASSIS TIGHTENING TORQUES............2-19 LUBRICATION POINTS AND LUBRICANT TYPES ........2-22 ENGINE....................

  • Page 24: General Specifications

    GENERAL SPECIFICATIONS YamahaR125.COM EAS20280 GENERAL SPECIFICATIONS Model Model 5D71 (Europe) Dimensions Overall length 2015 mm (79.3 in) Overall width 660 mm (26.0 in) Overall height 1065 mm (41.9 in) Seat height 818 mm (32.2 in) Wheelbase 1355 mm (53.3 in) Ground clearance 155 mm (6.10 in) Minimum turning radius...

  • Page 25: Engine Specifications

    ENGINE SPECIFICATIONS YamahaR125.COM EAS20290 ENGINE SPECIFICATIONS Engine Engine type Liquid cooled 4-stroke, SOHC Displacement 124.7 cm³ Cylinder arrangement Forward-inclined single cylinder Bore × stroke 52.0 × 58.6 mm (2.05 × 2.31 in) Compression ratio 11.20 :1 Standard compression pressure (at sea level) 550 kPa/600 r/min (78.2 psi/600 r/min) (5.5 kgf/cm²/600 r/min) Minimum–maximum...
  • Page 26 ENGINE SPECIFICATIONS YamahaR125.COM Thermostat Model/manufacturer 5YP/NIPPON THERMOSTAT Valve opening temperature 80.5–83.5 °C (176.9–182.3 °F) Valve full open temperature 95.0 °C (203.0 °F) Valve lift (full open) 3.0 mm (0.12 in) Radiator core Width 198.0 mm (7.80 in) Height 128.0 mm (5.04 in) Depth 24.0 mm (0.94 in) Water pump...
  • Page 27 ENGINE SPECIFICATIONS YamahaR125.COM Timing chain Model/number of links DID SCR-0404SV/96 Tensioning system Automatic Rocker arm/rocker arm shaft Rocker arm inside diameter 9.985–10.000 mm (0.3931–0.3937 in) Limit 10.015 mm (0.3943 in) Rocker arm shaft outside diameter 9.966–9.976 mm (0.3924–0.3928 in) Limit 9.941 mm (0.3914 in) Rocker-arm-to-rocker-arm-shaft clearance 0.009–0.034 mm (0.0004–0.0013 in)
  • Page 28 ENGINE SPECIFICATIONS YamahaR125.COM Limit 4.550 mm (0.1791 in) Valve-stem-to-valve-guide clearance (intake) 0.010–0.037 mm (0.0004–0.0015 in) Limit 0.080 mm (0.0032 in) Valve-stem-to-valve-guide clearance (exhaust) 0.025–0.052 mm (0.0010–0.0020 in) Limit 0.100 mm (0.0039 in) Valve stem runout 0.010 mm (0.0004 in) Cylinder head valve seat width (intake) 0.90–1.10 mm (0.0354–0.0433 in) Limit 1.6 mm (0.06 in)
  • Page 29 ENGINE SPECIFICATIONS YamahaR125.COM Height H 5.0 mm (0.20 in) Offset 0.50 mm (0.0197 in) Offset direction Intake side Piston pin bore inside diameter 14.002–14.013 mm (0.5513–0.5517 in) Limit 14.043 mm (0.5529 in) Piston pin outside diameter 13.995–14.000 mm (0.5510–0.5512 in) Limit 13.975 mm (0.5502 in) Piston-pin-to-piston-pin-bore clearance...
  • Page 30 ENGINE SPECIFICATIONS YamahaR125.COM Runout limit C 0.030 mm (0.0012 in) Big end side clearance D 0.110–0.410 mm (0.0043–0.0161 in) Big end radial clearance E 0.004–0.014 mm (0.0002–0.0006 in) Balancer Balancer drive method Gear Clutch Clutch type Wet, multiple-disc Clutch release method Inner push, cam push Clutch lever free play 10.0–15.0 mm (0.39–0.59 in)
  • Page 31 ENGINE SPECIFICATIONS YamahaR125.COM Shifting mechanism Shift mechanism type Shift drum and guide bar 5.76–5.89 mm (0.227–0.232 in) × 1 Shift fork thickness 4.76–4.89 mm (0.187–0.193 in) × 2 Shift fork thickness Decompression device Device type Auto decomp Air filter Air filter element Dry element Fuel pump Pump type...

  • Page 32: Chassis Specifications

    CHASSIS SPECIFICATIONS YamahaR125.COM EAS20300 CHASSIS SPECIFICATIONS Chassis Frame type Semi double cradle Caster angle 24.20 ° Trail 86.1 mm (3.39 in) Front wheel Wheel type Cast wheel Rim size 17xMT2.75 Rim material Aluminum Wheel travel 130.0 mm (5.12 in) Radial wheel runout limit 0.5 mm (0.02 in) Lateral wheel runout limit 1.0 mm (0.04 in)
  • Page 33 CHASSIS SPECIFICATIONS YamahaR125.COM Front disc brake Disc outside diameter × thickness 292.0 × 4.0 mm (11.50 × 0.16 in) Brake disc thickness limit 3.5 mm (0.14 in) Brake disc deflection limit 0.15 mm (0.0059 in) Brake pad lining thickness (inner) 4.5 mm (0.18 in) Limit 0.8 mm (0.03 in)
  • Page 34 CHASSIS SPECIFICATIONS YamahaR125.COM Rear suspension Type Swingarm (monocross) Spring/shock absorber type Coil spring/oil damper Rear shock absorber assembly travel 54.0 mm (2.13 in) Spring free length 162.0 mm (6.38 in) Installed length 155.0 mm (6.10 in) Spring rate K1 103.00 N/mm (588.13 lb/in) (10.50 kgf/mm) Spring stroke K1 0.0–54.0 mm (0.00–2.13 in) Optional spring available...

  • Page 35: Electrical Specifications

    TCI (digital) Advancer type Throttle position sensor and electrical Ignition timing (B.T.D.C.) 5.0°/1400 r/min Engine control unit Model/manufacturer 5D700/YAMAHA Ignition coil Model/manufacturer 2JN/YAMAHA Minimum ignition spark gap 6.0 mm (0.24 in) 2.16–2.64 Ω at 20 °C (68 °F) Primary coil resistance Secondary coil resistance 8.64–12.96 kΩ...
  • Page 36 High beam indicator light Coolant temperature warning light Engine trouble warning light Electric starting system System type Constant mesh Starter motor Model/manufacturer 3C1/YAMAHA Power output 0.20 kW 0.0315–0.0385 Ω Armature coil resistance Brush overall length 7.0 mm (0.28 in) Limit 3.50 mm (0.14 in)
  • Page 37 ELECTRICAL SPECIFICATIONS YamahaR125.COM Radiator fan Model/manufacturer SSW6101/PANASONIC Running rpm 4800 r/min Fan motor relay Model/manufacturer ACM33211 M05/MATSUSHITA Fuses Main fuse 20.0 A Headlight fuse 15.0 A Signaling system fuse 7.5 A Ignition fuse 7.5 A Radiator fan fuse 5.0 A Spare fuse 20.0 A Spare fuse...

  • Page 38: Tightening Torques

    TIGHTENING TORQUES YamahaR125.COM EAS20320 TIGHTENING TORQUES EAS20330 GENERAL TIGHTENING TORQUE SPECIFICATIONS This chart specifies tightening torques for stan- dard fasteners with a standard ISO thread pitch. Tightening torque specifications for special com- ponents or assemblies are provided for each chapter of this manual. To avoid warpage, tight- en multi-fastener assemblies in a crisscross pat- tern and progressive stages until the specified tightening torque is reached.

  • Page 39: Engine Tightening Torques

    30 Nm (3.0 m·kg, 22 ft·lb) Camshaft retainer bolt 7 Nm (0.7 m·kg, 5.1 ft·lb) Timing chain guide (intake side) 10 Nm (1.0 m·kg, 7.2 ft·lb) bolt Yamaha bond No.1215 Timing chain tensioner bolt 10 Nm (1.0 m·kg, 7.2 ft·lb) (Three Bond No.1215...
  • Page 40 TIGHTENING TORQUES YamahaR125.COM Thread Item Q’ty Tightening torque Remarks size Air induction system reed valve 10 Nm (1.0 m·kg, 7.2 ft·lb) bolt Exhaust pipe nut 20 Nm (2.0 m·kg, 14 ft·lb) Exhaust assembly bolt 20 Nm (2.0 m·kg, 14 ft·lb) Exhaust assembly bolt 20 Nm (2.0 m·kg, 14 ft·lb) Crankcase bolt...
  • Page 41 TIGHTENING TORQUES YamahaR125.COM Cylinder head tightening sequence: Generator cover tightening sequence: 3,11 2,10 Clutch cover tightening sequence: 2,12 3,13 Crankcase tightening sequence: 2,12 3,13 A. Left crankcase B. Right crankcase 2-18...

  • Page 42: Chassis Tightening Torques

    TIGHTENING TORQUES YamahaR125.COM EAS20350 CHASSIS TIGHTENING TORQUES Thread Item Q’ty Tightening torque Remarks size Upper bracket pinch bolt 23 Nm (2.3 m·kg, 17 ft·lb) Lower bracket pinch bolt 28 Nm (2.8 m·kg, 20 ft·lb) Front brake pipe bracket bolt 7 Nm (0.7 m·kg, 5.1 ft·lb) Lower ring nut (initial tightening 48 Nm (4.8 m·kg, 35 ft·lb) torque)
  • Page 43 TIGHTENING TORQUES YamahaR125.COM Thread Item Q’ty Tightening torque Remarks size Fuel tank front bolt 10 Nm (1.0 m·kg, 7.2 ft·lb) Fuel tank rear bolt 10 Nm (1.0 m·kg, 7.2 ft·lb) Mud guard bolt 7 Nm (0.7 m·kg, 5.1 ft·lb) Passenger seat front bolt 30 Nm (3.0 m·kg, 22 ft·lb) Passenger seat rear bolt 11 Nm (1.1 m·kg, 8.0 ft·lb)
  • Page 44 TIGHTENING TORQUES YamahaR125.COM • Retighten the lower ring nut to 13 Nm (1.3 m·kg, 9.4 ft·lb) with a torque wrench. 2-21...

  • Page 45: Lubrication Points And Lubricant Types

    LUBRICATION POINTS AND LUBRICANT TYPES YamahaR125.COM EAS20360 LUBRICATION POINTS AND LUBRICANT TYPES EAS20370 ENGINE Lubrication point Lubricant Oil seal lips Bearings Cylinder head bolt seats, cylinder head bolt threads and washers Water pump assembly O-rings Cylinder head cover gasket Connecting rod big end Piston pin Cylinder inner surface, piston, ring grooves, and piston rings Balancer O-rings...
  • Page 46 Clutch boss nut seat and clutch boss nut thread Main axle and pinion gears Drive axle and wheel gears Shift drum assembly Shift forks and shift fork guide bar Shift shaft Yamaha bond Crankshaft position sensor/stator assembly lead grommet No.1215 (Three Bond No.1215®) Yamaha bond Crankcase mating surfaces No.1215 (Three Bond...

  • Page 47: Chassis

    LUBRICATION POINTS AND LUBRICANT TYPES YamahaR125.COM EAS20380 CHASSIS Lubrication point Lubricant Front wheel oil seal lip Rear wheel oil seal lip Rear wheel drive hub oil seal lip Rear wheel and rear wheel drive hub mating surface Pivot shaft Pivot shaft bearing and spacer Pivot shaft dust cover inner surface Relay arm bearing, spacer and oil seal lips Swingarm bearing, spacer and oil seal lips...

  • Page 48: Lubrication System Chart And Diagrams

    LUBRICATION SYSTEM CHART AND DIAGRAMS YamahaR125.COM EAS20390 LUBRICATION SYSTEM CHART AND DIAGRAMS EAS20400 ENGINE OIL LUBRICATION CHART 2-25...
  • Page 49 LUBRICATION SYSTEM CHART AND DIAGRAMS YamahaR125.COM 1. Oil pump 2. Oil filter element 3. Crankshaft 4. Camshaft 5. Main axle 6. Drive axle 2-26...

  • Page 50: Lubrication Diagrams

    LUBRICATION SYSTEM CHART AND DIAGRAMS YamahaR125.COM EAS20410 LUBRICATION DIAGRAMS 2-27...
  • Page 51 LUBRICATION SYSTEM CHART AND DIAGRAMS YamahaR125.COM 1. Clutch push lever 2. Main axle 3. Drive axle 4. Crankshaft 5. Oil filter 6. Oil pump assembly 7. Oil strainer A. To cylinder head 2-28...
  • Page 52 LUBRICATION SYSTEM CHART AND DIAGRAMS YamahaR125.COM 2-29...
  • Page 53 LUBRICATION SYSTEM CHART AND DIAGRAMS YamahaR125.COM 1. Camshaft 2. Crankshaft 3. Main axle 4. Drive axle 2-30...

  • Page 54: Cooling System

    COOLING SYSTEM DIAGRAMS YamahaR125.COM EAS20420 COOLING SYSTEM DIAGRAMS 2-31...
  • Page 55 COOLING SYSTEM DIAGRAMS YamahaR125.COM 1. Radiator inlet hose 2. Coolant reservoir hose 3. Radiator cap 4. Radiator 5. Coolant reservoir breather hose 6. Coolant reservoir 7. Water pump breather hose 8. Water pump 9. Radiator outlet hose 2-32...

  • Page 56: Cable Routing

    CABLE ROUTING YamahaR125.COM EAS20430 CABLE ROUTING 2-33...
  • Page 57 CABLE ROUTING YamahaR125.COM 1. Front brake light switch lead 2. Right handlebar switch lead 3. Throttle cable 4. Main switch 5. Clutch cable 6. Clutch switch lead 7. Left handlebar switch lead 8. Sub-wire harness 9. Horn 10. Speed sensor lead 11.
  • Page 58 CABLE ROUTING YamahaR125.COM 2-35...
  • Page 59 CABLE ROUTING YamahaR125.COM 1. Throttle body 2. Wire harness 3. Ignition coil 4. Spark plug lead 5. Sub-wire harness 6. Front brake light switch lead 7. Throttle cable 8. Right handlebar switch lead 9. Right headlight assembly lead 10. Left headlight assembly lead 11.
  • Page 60 CABLE ROUTING YamahaR125.COM 2-37...
  • Page 61 CABLE ROUTING YamahaR125.COM 1. Battery breather hose 2. Wire harness 3. Starter motor lead 4. Rear brake light switch lead 5. Rear brake hose A. Fasten the battery breather hose with the holder. 2-38...
  • Page 62 CABLE ROUTING YamahaR125.COM 2-39...
  • Page 63 CABLE ROUTING YamahaR125.COM 1. Front brake hose 2. Throttle cable 3. Left handlebar switch lead 4. Clutch cable 5. Wire harness (to horn) 6. Ignition coil 7. Air filter case silencer hose 8. Sidestand switch lead 9. Coolant reservoir hose 10.
  • Page 64 CABLE ROUTING YamahaR125.COM 13 14 2-41...
  • Page 65 CABLE ROUTING YamahaR125.COM 1. Air filter case silencer hose 2. Wire harness 3. Battery 4. Lean angle sensor 5. Tail/brake light lead 6. Sidestand switch lead 7. Neutral switch 8. Crankshaft position sensor/stator coil lead 9. Negative battery lead 10. Rectifier/regulator 11.
  • Page 66 CABLE ROUTING YamahaR125.COM 2-43...
  • Page 67 CABLE ROUTING YamahaR125.COM 1. Coolant reservoir hose 2. Radiator inlet hose 3. Spark plug lead 4. Wire harness 5. FID (fast idle solenoid) lead 6. Fuel injector lead 7. Rear brake light switch lead 8. Throttle body sensor assembly 9. Ignition coil leads 10.
  • Page 68 CABLE ROUTING YamahaR125.COM 2-45...
  • Page 69 CABLE ROUTING YamahaR125.COM 1. Positive battery lead 2. Starter relay 3. Radiator fan motor relay 4. Turn signal relay 5. Lean angle sensor 6. Rear right turn signal light lead 7. License plate light lead 8. Rear left turn signal light lead 9.
  • Page 70 CABLE ROUTING YamahaR125.COM 2-47...
  • Page 71 YamahaR125.COM PERIODIC CHECKS AND ADJUSTMENTS PERIODIC MAINTENANCE ................3-1 INTRODUCTION ..................3-1 PERIODIC MAINTENANCE AND LUBRICATION CHART....... 3-1 ENGINE ......................3-3 ADJUSTING THE VALVE CLEARANCE ..........3-3 ADJUSTING THE EXHAUST GAS VOLUME ........... 3-5 ADJUSTING THE ENGINE IDLING SPEED ..........3-6 ADJUSTING THE THROTTLE CABLE FREE PLAY ........
  • Page 72 YamahaR125.COM ELECTRICAL SYSTEM................. 3-27 CHECKING AND CHARGING THE BATTERY........3-27 CHECKING THE FUSES ................ 3-27 REPLACING THE HEADLIGHT BULBS ..........3-27 ADJUSTING THE HEADLIGHT BEAMS..........3-28...
  • Page 73 YamahaR125.COM...

  • Page 74: Periodic Maintenance

    UK, a mileage-based maintenance, is performed instead. • From 30000 km (17500 mi), repeat the maintenance intervals starting from 6000 km (3500 mi). • Items marked with an asterisk should be performed by a Yamaha dealer as they require special tools, data and technical skills.
  • Page 75 PERIODIC MAINTENANCE YamahaR125.COM ODOMETER READING CHECK OR MAINTENANCE ANNUAL ITEM 1000 km 6000 km 12000 km 18000 km 24000 km CHECK (600 mi) (3500 mi) (7000 mi) (10500 mi) (14000 mi) • Check bearing play and steer- √ √ √ √...

  • Page 76: Engine

    ENGINE YamahaR125.COM EAS20471 ENGINE EAS20520 ADJUSTING THE VALVE CLEARANCE The following procedure applies to all of the valves. NOTE: • Valve clearance adjustment should be made on a cold engine, at room temperature. • When the valve clearance is to be measured or 6.
  • Page 77 ENGINE YamahaR125.COM • Hold the adjusting screw to prevent it from moving and tighten the locknut to specifica- tion. Valve adjusting screw locknut 7 Nm (0.7 m·kg, 5.1 ft·lb) d. Measure the valve clearance again. e. If the valve clearance is still out of specifica- tion, repeat all of the valve clearance adjust- ment steps until the specified clearance is L LLL...

  • Page 78: Adjusting The Exhaust Gas Volume

    ENGINE YamahaR125.COM FI Diagnostic Tool DIAG 6. Press the “UP” button “4” to select the CO ad- 13.Connect: justment mode “CO” or the diagnostic mode • Spark plug cap “DIAG”. 14.Install: 7. After selecting “CO”, press the “MODE” but- • Fuel tank ton.

  • Page 79: Adjusting The Engine Idling Speed

    ENGINE YamahaR125.COM 15.Install: 8. Remove: • Rider seat • Digital tachometer Refer to “GENERAL CHASSIS” on page 4-1. 9. Install: • Fuel tank EAS20610 Refer to “FUEL TANK” on page 7-1. ADJUSTING THE ENGINE IDLING SPEED • Right side panel NOTE: •...

  • Page 80: Checking The Spark Plug

    ENGINE YamahaR125.COM EWA12930 WARNING Direction “a” Throttle cable free play is increased. After adjusting the throttle cable free play, Direction “b” start the engine and turn the handlebar to the Throttle cable free play is decreased. right or left to ensure that this does not cause the engine idling speed to change.

  • Page 81: Checking The Ignition Timing

    ENGINE YamahaR125.COM • Digital tachometer Timing light 90890-03141 Inductive clamp timing light YU-03141 8. Install: • Spark plug Spark plug 13 Nm (1.3 m·kg, 9.4 ft·lb) NOTE: 5. Check: Before installing the spark plug, clean the spark • Ignition timing plug and gasket surface.

  • Page 82: Measuring The Compression Pressure

    ENGINE YamahaR125.COM 8. Install: • Compression gauge “2” • Timing mark accessing screw Extension (along with the O-ring 90890-04082 9. Install: Compression gauge • Left lower side cowling 90890-03081 • Right side cover Engine compression tester • Rider seat YU-33223 Refer to “GENERAL CHASSIS”...

  • Page 83: Checking The Engine Oil Level

    ENGINE YamahaR125.COM Compression pressure (with oil applied into the cylinder) Reading Diagnosis Higher than without Piston ring(s) wear or damage → Repair. Piston, valves, cylin- der head gasket or Same as without oil piston possibly defec- tive → Repair. L LLL L LLL L LLL L LLL...

  • Page 84: Changing The Engine Oil

    ENGINE YamahaR125.COM 4. Start the engine, warm it up for several min- utes, and then turn it off. 5. Check the engine oil level again. NOTE: Before checking the engine oil level, wait a few minutes until the oil has settled. EAS20810 CHANGING THE ENGINE OIL 1.

  • Page 85: Adjusting The Clutch Cable Free Play

    ENGINE YamahaR125.COM • Right bottom side cowling Engine oil quantity Refer to “GENERAL CHASSIS” on page 4-1. Total amount 1.15 L (1.22 US qt) (1.01 Imp.qt) EAS20870 ADJUSTING THE CLUTCH CABLE FREE Without oil filter element replace- PLAY ment 1. Check: 0.95 L (1.00 US qt) (0.84 Imp.qt) With oil filter element replace- •...

  • Page 86: Cleaning The Air Filter Element

    ENGINE YamahaR125.COM NOTE: If the specified clutch cable free play cannot be obtained on the handlebar end of the cable, use the adjusting nut on the engine end. L LLL L LLL L LLL L LLL L LLL 3. Remove: •...

  • Page 87: Checking The Throttle Body Joint And Air Filter Case Joint

    ENGINE YamahaR125.COM 2. Lift the fuel tank. (Do not disconnect the fuel ECA5D71025 CAUTION: hose, drain hose, and couplers.) Never operate the engine without the air filter 3. Check: element installed. Unfiltered air will cause • Fuel hose “1” rapid wear of engine parts and may damage Cracks/damage →...

  • Page 88: Checking The Exhaust System

    ENGINE YamahaR125.COM EAS21080 ECA5D71035 CHECKING THE EXHAUST SYSTEM CAUTION: 1. Check: • Adding water instead of coolant lowers the • Exhaust assembly “1” antifreeze content of the coolant. If water is Cracks/damage → Replace. used instead of coolant, check and, if nec- •...
  • Page 89 ENGINE YamahaR125.COM 2. Remove: • Radiator cap “1” 7. Drain: • Coolant (from the coolant reservoir) EWA13030 WARNING 8. Connect: A hot radiator is under pressure. Therefore, • Coolant reservoir hose do not remove the radiator cap when the en- 9.
  • Page 90 ENGINE YamahaR125.COM ECA5D71036 CAUTION: • Adding water instead of coolant lowers the antifreeze content of the coolant. If water is used instead of coolant, check and, if nec- essary, correct the antifreeze concentra- tion of the coolant. • Use only distilled water. However, if dis- tilled water is not available, soft water may be used.

  • Page 91: Chassis

    CHASSIS YamahaR125.COM EAS21140 EWA5D71014 CHASSIS WARNING A soft or spongy feeling in the brake pedal EAS21200 can indicate the presence of air in the brake ADJUSTING THE REAR DISC BRAKE system. Before the vehicle is operated, the 1. Check: air must be removed by bleeding the brake •...

  • Page 92: Checking The Front Brake Pads

    CHASSIS YamahaR125.COM 1. Operate the brake. 2. Check: • Front brake pad Wear indicator grooves “a” have almost dis- appeared → Replace the brake pads as a set. Refer to “FRONT BRAKE” on page 4-17. EAS21260 CHECKING THE REAR BRAKE PADS The following procedure applies to all of the brake pads.

  • Page 93: Checking The Rear Brake Hose

    CHASSIS YamahaR125.COM • the brake fluid level is very low. • brake operation is faulty. NOTE: • Be careful not to spill any brake fluid or allow the brake master cylinder reservoir or brake fluid reservoir to overflow. • When bleeding the hydraulic brake system, make sure there is always enough brake fluid before applying the brake.

  • Page 94: Adjusting The Drive Chain Slack

    CHASSIS YamahaR125.COM f. Fully pull the brake lever or fully press down 2. Turn the rear wheel several times and find the the brake pedal and hold it in position. tightest position on the drive chain. g. Loosen the bleed screw. 3.

  • Page 95: Lubricating The Drive Chain

    CHASSIS YamahaR125.COM d. Tighten the wheel axle nut to specification. 4. Adjust: • Steering head Wheel axle nut M MMM M MMM M MMM M MMM M MMM 85 Nm (8.5 m·kg, 61 ft·lb) a. Remove the lock washer “1”, the upper ring nut “2”, and the rubber washer “3”.

  • Page 96: Checking The Front Fork

    CHASSIS YamahaR125.COM d. Check the steering head for looseness or binding by turning the front fork all the way in both directions. If any binding is felt, remove the lower bracket and check the upper and lower bearings. Refer to “STEERING HEAD” on page 4-52. e.
  • Page 97 CHASSIS YamahaR125.COM • When using a tube tire, be sure to install the Tire air pressure (measured on correct tube. cold tires) • Always replace a new tube tire and a new Loading condition tube as a set. 0–90 kg (0–198 lb) •...

  • Page 98: Checking The Wheels

    CHASSIS YamahaR125.COM EWA13270 WARNING Rear tire Size Damaged outer cable may cause the cable to 130/70–17 M/C 62H corrode and interfere with its movement. Re- Manufacturer/model place damaged outer cable and inner cables PIRELLI/SPORT DEMON as soon as possible. Manufacturer/model 1.

  • Page 99: Lubricating The Rear Suspension

    CHASSIS YamahaR125.COM EAS21740 LUBRICATING THE REAR SUSPENSION Lubricate the pivoting point and metal-to-metal moving parts of the rear suspension. Recommended lubricant Lithium-soap-based grease 3-26...

  • Page 100: Electrical System

    ELECTRICAL SYSTEM YamahaR125.COM EAS21750 EWA13320 ELECTRICAL SYSTEM WARNING Since the headlight bulb gets extremely hot, EAS21760 keep flammable products and your hands CHECKING AND CHARGING THE BATTERY away from the bulb until it has cooled down. Refer to “ELECTRICAL COMPONENTS” on page 8-57.
  • Page 101 ELECTRICAL SYSTEM YamahaR125.COM M MMM M MMM M MMM M MMM M MMM a. Turn the adjusting screw “1” in direction “a” or “b”. Direction “a” Headlight beam is lowered. Direction “b” Headlight beam is raised. 4. Remove: • Headlight bulb “1” EWA13320 WARNING Since the headlight bulb gets extremely hot,...
  • Page 102 ELECTRICAL SYSTEM YamahaR125.COM 3-29...
  • Page 103 YamahaR125.COM CHASSIS GENERAL CHASSIS..................4-1 INSTALLING THE AIR FILTER CASE ............4-5 FRONT WHEEL....................4-6 REMOVING THE FRONT WHEEL (DISC)..........4-8 DISASSEMBLING THE FRONT WHEEL..........4-8 CHECKING THE FRONT WHEEL ............4-8 ASSEMBLING THE FRONT WHEEL............4-9 ADJUSTING THE FRONT WHEEL STATIC BALANCE ......4-9 INSTALLING THE FRONT WHEEL (DISC) ..........
  • Page 104 YamahaR125.COM HANDLEBARS ....................4-39 REMOVING THE HANDLEBARS ............4-41 CHECKING THE HANDLEBARS ............4-41 INSTALLING THE HANDLEBARS ............4-41 FRONT FORK....................4-44 REMOVING THE FRONT FORK LEGS..........4-47 DISASSEMBLING THE FRONT FORK LEGS ........4-47 CHECKING THE FRONT FORK LEGS ..........4-48 ASSEMBLING THE FRONT FORK LEGS ..........
  • Page 105 YamahaR125.COM...
  • Page 106 GENERAL CHASSIS YamahaR125.COM EAS21830 GENERAL CHASSIS Removing the seats and battery 30 Nm (3.0 m kg, 22 ft • • 11 Nm (1.1 m kg, 8.0 ft • • Order Job/Parts to remove Q’ty Remarks Rider seat Passenger seat Negative battery lead Disconnect.
  • Page 107 GENERAL CHASSIS YamahaR125.COM Removing the rear side cowlings 7 Nm (0.7 m kg, 5.1 ft 7 Nm (0.7 m kg, 5.1 ft • • • • Order Job/Parts to remove Q’ty Remarks Refer to “GENERAL CHASSIS” on page Rider seat/Passenger seat 4-1.
  • Page 108 GENERAL CHASSIS YamahaR125.COM Removing the side cowlings and front cowling assembly 23 Nm (2.3 m kg, 17 ft • • Order Job/Parts to remove Q’ty Remarks Refer to “GENERAL CHASSIS” on page Side panels 4-1. Side cover Upper side cowling Front turn signal light coupler Bottom cowling Lower side cowling...
  • Page 109 GENERAL CHASSIS YamahaR125.COM Removing the air filter case 2 Nm (0.2 m kg, 1.4 ft • • 10 Nm (1.0 m kg, 7.2 ft • • Order Job/Parts to remove Q’ty Remarks Refer to “GENERAL CHASSIS” on page Fuel tank cover 4-1.

  • Page 110: General Chassis

    GENERAL CHASSIS YamahaR125.COM EAS5D71027 INSTALLING THE AIR FILTER CASE 1. Install: • Air filter case joint clamp NOTE: Align the projection “a” on the air filter case with the slot “b” in the air filter case joint clamp.

  • Page 111: Front Wheel

    FRONT WHEEL YamahaR125.COM EAS21870 FRONT WHEEL Removing the front wheel and brake disc 7 Nm (0.7 m kg, 5.1 ft 7 Nm (0.7 m kg, 5.1 ft • • • • 59 Nm (5.9 m kg, 43 ft • • 14 Nm (1.4 m kg, 10 ft •...
  • Page 112 FRONT WHEEL YamahaR125.COM Disassembling the front wheel Order Job/Parts to remove Q’ty Remarks Oil seal Bearing Spacer Bearing For assembly, reverse the disassembly pro- cedure.

  • Page 113: Removing The Front Wheel (Disc)

    FRONT WHEEL YamahaR125.COM EAS21890 REMOVING THE FRONT WHEEL (DISC) 1. Stand the vehicle on a level surface. EWA13120 WARNING Securely support the vehicle so that there is no danger of it falling over. 2. Elevate: • Front wheel NOTE: Place the vehicle on a suitable stand so that the L LLL L LLL L LLL...

  • Page 114: Assembling The Front Wheel

    FRONT WHEEL YamahaR125.COM 4. Check: L LLL L LLL L LLL L LLL L LLL • Wheel bearings EAS21970 Front wheel turns roughly or is loose → Re- ADJUSTING THE FRONT WHEEL STATIC place the wheel bearings. BALANCE • Oil seal NOTE: Damage/wear →...

  • Page 115: Installing The Front Wheel (Disc)

    FRONT WHEEL YamahaR125.COM M MMM M MMM M MMM M MMM M MMM a. Turn the front wheel and make sure it stays at each position shown. f. Repeat steps (c) through (e) several times until all the marks come to rest at the same spot.
  • Page 116 FRONT WHEEL YamahaR125.COM 3. Lubricate: ECA5D71028 CAUTION: • Front wheel axle Before tightening the wheel axle, push down • Oil seal lip hard on the handlebar(s) several times and • Speed sensor lip check if the front fork rebounds smoothly. Recommended lubricant M MMM M MMM...

  • Page 117: Rear Wheel

    REAR WHEEL YamahaR125.COM EAS22020 REAR WHEEL Removing the rear wheel 85 Nm (8.5 m kg, 61 ft • • 7 Nm (0.7 m kg, 5.1 ft • • 7 Nm (0.7 m kg, 5.1 ft • • Order Job/Parts to remove Q’ty Remarks NOTE:...
  • Page 118 REAR WHEEL YamahaR125.COM Removing the brake disc and rear wheel sprocket 18 Nm (1.8 m kg, 13 ft • • 43 Nm (4.3 m kg, 31 ft • • Order Job/Parts to remove Q’ty Remarks Rear brake disc Rear wheel sprocket Oil seal Bearing Rear wheel drive hub...
  • Page 119 REAR WHEEL YamahaR125.COM Disassembling the rear wheel Order Job/Parts to remove Q’ty Remarks Bearing Spacer Oil seal Bearing For assembly, reverse the disassembly pro- cedure. 4-14...

  • Page 120: Removing The Rear Wheel (Disc)

    REAR WHEEL YamahaR125.COM Refer to “CHECKING THE TIRES” on page EAS22040 REMOVING THE REAR WHEEL (DISC) 3-23 and “CHECKING THE WHEELS” on 1. Stand the vehicle on a level surface. page 3-25. EWA13120 3. Measure: WARNING • Radial wheel runout Securely support the vehicle so that there is •...

  • Page 121: Assembling The Rear Wheel

    REAR WHEEL YamahaR125.COM M MMM M MMM M MMM M MMM M MMM a. Remove the self-locking nuts and the rear Rear brake disc bolt 18 Nm (1.8 m·kg, 13 ft·lb) wheel sprocket. LOCTITE® b. Clean the rear wheel drive hub with a clean cloth, especially the surfaces that contact the NOTE: sprocket.

  • Page 122: Front Brake

    FRONT BRAKE YamahaR125.COM EAS22210 FRONT BRAKE Removing the front brake pads 30 Nm (3.0 m kg, 22 ft • • 7 Nm (0.7 m kg, 5.1 ft • • 14 Nm (1.4 m kg, 10 ft • • Order Job/Parts to remove Q’ty Remarks Brake hose holder...
  • Page 123 FRONT BRAKE YamahaR125.COM Removing the front brake master cylinder 30 Nm (3.0 m kg, 22 ft • • 9 Nm (0.9 m kg, 6.5 ft • • Order Job/Parts to remove Q’ty Remarks Drain. Brake fluid Refer to “BLEEDING THE HYDRAULIC BRAKE SYSTEM”...
  • Page 124 FRONT BRAKE YamahaR125.COM Removing the front brake caliper 30 Nm (3.0 m kg, 22 ft • • 7 Nm (0.7 m kg, 5.1 ft • • 30 Nm (3.0 m kg, 22 ft • • Order Job/Parts to remove Q’ty Remarks Drain.
  • Page 125 FRONT BRAKE YamahaR125.COM Disassembling the front brake caliper Order Job/Parts to remove Q’ty Remarks Brake pad clip Brake pad pin Brake pad Brake pad spring Brake caliper bracket Brake pad support Brake caliper body For assembly, reverse the disassembly pro- cedure.

  • Page 126: Introduction

    FRONT BRAKE YamahaR125.COM EAS22220 M MMM M MMM M MMM M MMM M MMM INTRODUCTION a. Place the vehicle on a suitable stand so that EWA14100 the front wheel is elevated. WARNING b. Before measuring the front brake disc deflec- Disc brake components rarely require disas- tion, turn the handlebar to the left or right to sembly.

  • Page 127: Replacing The Front Brake Pads

    FRONT BRAKE YamahaR125.COM 2. Install: • Brake pad support • Brake pad spring • Brake pads NOTE: Always install new brake pads, a new brake pad spring and a new brake pad support as a set. M MMM M MMM M MMM M MMM M MMM...

  • Page 128: Removing The Front Brake Caliper

    FRONT BRAKE YamahaR125.COM EAS22380 CHECKING THE FRONT BRAKE CALIPER Front brake caliper bolt 30 Nm (3.0 m·kg, 22 ft·lb) Recommended brake component replace- LOCTITE® ment schedule Brake pads If necessary 4. Check: • Brake fluid level Piston seals Every two years Below the minimum level mark “a”...

  • Page 129: Installing The Front Brake Caliper

    FRONT BRAKE YamahaR125.COM • Whenever a brake caliper is disassembled, Front brake caliper bolt replace the brake caliper dust seals and 30 Nm (3.0 m·kg, 22 ft·lb) piston seals. LOCTITE® Front brake hose holder Recommended fluid 7 Nm (0.7 m·kg, 5.1 ft·lb) DOT 4 Refer to “REPLACING THE FRONT BRAKE EAS22420...

  • Page 130: Removing The Front Brake Master Cylinder

    FRONT BRAKE YamahaR125.COM 3. Check: • Brake hose Cracks/damage/wear → Replace. EAS22520 ASSEMBLING THE FRONT BRAKE MASTER CYLINDER EWA13520 WARNING • Before installation, all internal brake com- ponents should be cleaned and lubricated with clean or new brake fluid. 7. Check: •...
  • Page 131 FRONT BRAKE YamahaR125.COM NOTE: Before fully installing the front brake light switch, be sure to completely install the rubber cover over the switch. Also, be sure not to twist the front brake light switch lead when screwing in the switch. 4.
  • Page 132 FRONT BRAKE YamahaR125.COM 7. Check: • Brake lever operation Soft or spongy feeling → Bleed the brake sys- tem. Refer to “BLEEDING THE HYDRAULIC BRAKE SYSTEM” on page 3-20. 4-27...

  • Page 133: Rear Brake

    REAR BRAKE YamahaR125.COM EAS22550 REAR BRAKE Removing the rear brake pads 14 Nm (1.4 m kg, 10 ft • • 18 Nm (1.8 m kg, 13 ft • • Order Job/Parts to remove Q’ty Remarks Rear wheel Refer to “REAR WHEEL” on page 4-12. Rear brake caliper Brake pad retaining bolt Rear brake pad...
  • Page 134 REAR BRAKE YamahaR125.COM Removing the rear brake master cylinder 24 Nm (2.4 m kg, 17 ft • • 13 Nm (1.3 m kg, 9.4 ft • • Order Job/Parts to remove Q’ty Remarks Refer to “GENERAL CHASSIS” on page Right side panel 4-1.
  • Page 135 REAR BRAKE YamahaR125.COM Disassembling the rear brake master cylinder 17 Nm (1.7 m kg, 12 ft • • Order Job/Parts to remove Q’ty Remarks Brake hose joint Brake master cylinder kit Brake master cylinder body For assembly, reverse the disassembly pro- cedure.
  • Page 136 REAR BRAKE YamahaR125.COM Removing the rear brake caliper 7 Nm (0.7 m kg, 5.1 ft • • 30 Nm (3.0 m kg, 22 ft • • Order Job/Parts to remove Q’ty Remarks Drain. Brake fluid Refer to “BLEEDING THE HYDRAULIC BRAKE SYSTEM”...
  • Page 137 REAR BRAKE YamahaR125.COM Disassembling the rear brake caliper 14 Nm (1.4 m kg, 10 ft • • 18 Nm (1.8 m kg, 13 ft • • Order Job/Parts to remove Q’ty Remarks Brake pad retaining bolt Rear brake pad Brake pad spring Brake caliper bracket Brake caliper piston Brake caliper piston dust seal...

  • Page 138: Introduction

    REAR BRAKE YamahaR125.COM EAS22560 INTRODUCTION Brake disc thickness limit EWA14100 3.5 mm (0.14 in) WARNING Disc brake components rarely require disas- 5. Adjust: sembly. Therefore, always follow these pre- • Brake disc deflection ventive measures: Refer to “CHECKING THE FRONT BRAKE •...

  • Page 139: Removing The Rear Brake Caliper

    REAR BRAKE YamahaR125.COM NOTE: Brake pad lining thickness (in- Install the brake pad spring as shown. ner) 5.5 mm (0.22 in) Limit 1.0 mm (0.04 in) Brake pad lining thickness (out- 5.5 mm (0.22 in) Limit 1.0 mm (0.04 in) L LLL L LLL L LLL...

  • Page 140: Disassembling The Rear Brake Caliper

    REAR BRAKE YamahaR125.COM 1. Remove: • Union bolt “1” • Copper washers “2” • Brake hose “3” b. Remove the brake caliper piston seal and dust seal. L LLL L LLL L LLL L LLL L LLL EAS22640 CHECKING THE REAR BRAKE CALIPER NOTE: Put the end of the brake hose into a container Recommended brake component...

  • Page 141: Assembling The Rear Brake Caliper

    REAR BRAKE YamahaR125.COM EWA5D71012 WARNING Whenever a brake caliper is disassembled, replace the brake caliper piston dust seals and piston seals. 2. Check: • Brake caliper bracket Cracks/damage → Replace. EAS22650 ASSEMBLING THE REAR BRAKE CALIPER 2. Install: EWA5D71017 • Brake pad spring WARNING •...

  • Page 142: Removing The Rear Brake Master Cylinder

    REAR BRAKE YamahaR125.COM 5. Bleed: • Brake system Refer to “BLEEDING THE HYDRAULIC BRAKE SYSTEM” on page 3-20. 6. Check: • Brake fluid level Below the minimum level mark “a” → Add the recommended brake fluid to the proper level. Refer to “CHECKING THE BRAKE FLUID LEVEL”...

  • Page 143: Installing The Rear Brake Master Cylinder

    REAR BRAKE YamahaR125.COM EAS22740 ECA13540 INSTALLING THE REAR BRAKE MASTER CAUTION: CYLINDER Brake fluid may damage painted surfaces 1. Install: and plastic parts. Therefore, always clean up • Copper washers “1” any spilt brake fluid immediately. • Brake hose “2” 3.

  • Page 144: Handlebars

    HANDLEBARS YamahaR125.COM EAS22850 HANDLEBARS Removing the handlebars 9 Nm (0.9 m kg, 6.5 ft • • 26 Nm (2.6 m kg, 19 ft 9 Nm (0.9 m kg, 6.5 ft • • • • 9 Nm (0.9 m kg, 6.5 ft •...
  • Page 145 HANDLEBARS YamahaR125.COM Removing the handlebars 9 Nm (0.9 m kg, 6.5 ft • • 26 Nm (2.6 m kg, 19 ft 9 Nm (0.9 m kg, 6.5 ft • • • • 9 Nm (0.9 m kg, 6.5 ft • •...

  • Page 146: Removing The Handlebars

    HANDLEBARS YamahaR125.COM • Align the mating surfaces of the brake master EAS22870 REMOVING THE HANDLEBARS cylinder holder with the punch mark “b” on the 1. Stand the vehicle on a level surface. handlebar. EWA13120 • First, tighten the front bolt, then the rear bolt. WARNING Securely support the vehicle so that there is no danger of it falling over.
  • Page 147 HANDLEBARS YamahaR125.COM NOTE: Align the projection “a” on the clutch switch with the slit “b” in the clutch lever holder. 5. Install: • Right grip end “1” NOTE: There should be 1–3 mm (0.04–0.12 in) of clear- 8. Connect: ance “a” between the throttle grip and the right •...
  • Page 148 HANDLEBARS YamahaR125.COM NOTE: There should be 3 mm (0.12 in) of clearance “a” between the handlebar grip and the grip end. L LLL L LLL L LLL L LLL L LLL 12.Check: • Cable routing NOTE: Make sure the main switch lead, brake hose, throttle cable, clutch cable, and handlebar switch leads are routed properly.

  • Page 149: Front Fork

    FRONT FORK YamahaR125.COM EAS22950 FRONT FORK Removing the front fork legs 9 Nm (0.9 m kg, 6.5 ft • • 23 Nm (2.3 m kg, 17 ft • • 28 Nm (2.8 m kg, 20 ft • • 7 Nm (0.7 m kg, 5.1 ft •...
  • Page 150 FRONT FORK YamahaR125.COM Disassembling the front fork legs 28 Nm (2.8 m kg, 20 ft • • Order Job/Parts to remove Q’ty Remarks The following procedure applies to both of the front fork legs. Rubber cap Clip Front fork cap O-ring Spacer Washer...
  • Page 151 FRONT FORK YamahaR125.COM Disassembling the front fork legs 28 Nm (2.8 m kg, 20 ft • • Order Job/Parts to remove Q’ty Remarks Outer tube bushing Outer tube For assembly, reverse the disassembly pro- cedure. 4-46...

  • Page 152: Removing The Front Fork Legs

    FRONT FORK YamahaR125.COM EAS22960 NOTE: REMOVING THE FRONT FORK LEGS Push the front fork cap in the direction of the ar- The following procedure applies to both of the row shown in the illustration to remove the clip. front fork legs. 1.

  • Page 153: Checking The Front Fork Legs

    FRONT FORK YamahaR125.COM NOTE: While holding the damper rod with the damper rod holder “2” and T-handle “3”, loosen the damper rod bolt. Damper rod holder 90890-01294 Damping rod holder set YM-01300 T-handle 3. Check: 90890-01326 • Damper rod T-handle 3/8" drive 60 cm long Damage/wear →...

  • Page 154: Front Fork

    FRONT FORK YamahaR125.COM Recommended oil Fork oil 10W or equivalent 3. Tighten: • Damper rod bolt “1” Damper rod bolt 28 Nm (2.8 m·kg, 20 ft·lb) NOTE: 5. Install: While holding the damper rod with the damper • Oil seal “1” rod holder “2”...
  • Page 155 FRONT FORK YamahaR125.COM Recommended oil Fork oil 10W or equivalent Quantity 235.0 cm³ (7.95 US oz) (8.29 Imp.oz) ECA14230 CAUTION: • Be sure to use the recommended fork oil. Other oils may have an adverse effect on front fork performance. 6.

  • Page 156: Installing The Front Fork Legs

    FRONT FORK YamahaR125.COM 12.Install: 2. Tighten: • Fork spring “1” • Lower bracket pinch bolt “1” NOTE: Lower bracket pinch bolt Install the spring with the smaller pitch “a” facing 28 Nm (2.8 m·kg, 20 ft·lb) • Upper bracket pinch bolt “2” Upper bracket pinch bolt 23 Nm (2.3 m·kg, 17 ft·lb) •...

  • Page 157: Steering Head

    STEERING HEAD YamahaR125.COM EAS23090 STEERING HEAD Removing the lower bracket 110 Nm (11.0 m kg, 80 ft • • 11 Nm (1.1 m kg, 8.0 ft • • 1st 48 Nm (4.8 m kg, 35 ft • • 7 Nm (0.7 m kg, 5.1 ft •...
  • Page 158 STEERING HEAD YamahaR125.COM Removing the lower bracket 110 Nm (11.0 m kg, 80 ft • • 11 Nm (1.1 m kg, 8.0 ft • • 1st 48 Nm (4.8 m kg, 35 ft • • 7 Nm (0.7 m kg, 5.1 ft •...

  • Page 159: Removing The Lower Bracket

    STEERING HEAD YamahaR125.COM b. Remove the bearing race from the lower EAS23110 REMOVING THE LOWER BRACKET bracket with a floor chisel “2” and hammer. 1. Stand the vehicle on a level surface. c. Install a new dust seal and new bearing rac- EWA13120 WARNING ECA5D71039...
  • Page 160 STEERING HEAD YamahaR125.COM • Upper ring nut • Lock washer Refer to “CHECKING AND ADJUSTING THE STEERING HEAD” on page 3-22. 3. Install: • Upper bracket • Steering stem nut NOTE: Temporarily tighten the steering stem nut. 4. Install: • Front fork legs Refer to “FRONT FORK”...

  • Page 161: Rear Shock Absorber Assembly

    REAR SHOCK ABSORBER ASSEMBLY YamahaR125.COM EAS23160 REAR SHOCK ABSORBER ASSEMBLY Removing the rear shock absorber assembly 44 Nm (4.4 m kg, 32 ft • • 44 Nm (4.4 m kg, 32 ft • • Order Job/Parts to remove Q’ty Remarks Refer to “GENERAL CHASSIS”...

  • Page 162: Removing The Rear Shock Absorber Assembly

    REAR SHOCK ABSORBER ASSEMBLY YamahaR125.COM EAS23230 REMOVING THE REAR SHOCK ABSORBER Recommended lubricant ASSEMBLY Lithium-soap-based grease 1. Stand the vehicle on a level surface. 2. Install: EWA13120 WARNING • Bearing “1” Securely support the vehicle so that there is (to the relay arm) no danger of it falling over.
  • Page 163 REAR SHOCK ABSORBER ASSEMBLY YamahaR125.COM 2. Tighten: • Rear shock absorber assembly upper nut Rear shock absorber assembly upper nut 44 Nm (4.4 m·kg, 32 ft·lb) • Relay arm nut Relay arm nut 44 Nm (4.4 m·kg, 32 ft·lb) • Rear shock absorber assembly lower nut Rear shock absorber assembly lower nut 44 Nm (4.4 m·kg, 32 ft·lb)

  • Page 164: Swingarm

    SWINGARM YamahaR125.COM EAS23330 SWINGARM Removing the swingarm 81Nm (8.1 m kg, 59 ft 7 Nm (0.7 m kg, 5.1 ft 7 Nm (0.7 m kg, 5.1 ft • • • • • • 7 Nm (0.7 m kg, 5.1 ft •...
  • Page 165 SWINGARM YamahaR125.COM Removing the swingarm 81Nm (8.1 m kg, 59 ft 7 Nm (0.7 m kg, 5.1 ft 7 Nm (0.7 m kg, 5.1 ft • • • • • • 7 Nm (0.7 m kg, 5.1 ft • • 7 Nm (0.7 m kg, 5.1 ft •...

  • Page 166: Removing The Swingarm

    SWINGARM YamahaR125.COM EAS23350 REMOVING THE SWINGARM 1. Stand the vehicle on a level surface. EWA13120 WARNING Securely support the vehicle so that there is no danger of it falling over. NOTE: Place the vehicle on a suitable stand so that the rear wheel is elevated.

  • Page 167: Installing The Swingarm

    SWINGARM YamahaR125.COM • Bearings NOTE: Damage/pitting → Replace. Temporarily tighten the pivot shaft nut. c. Turn the swingarm adjusting collar out to EAS23380 INSTALLING THE SWINGARM tighten it and so that it contacts the dust cover 1. Lubricate: on the swingarm. •...

  • Page 168: Chain Drive

    CHAIN DRIVE YamahaR125.COM EAS23400 CHAIN DRIVE Removing the drive chain 10 Nm (1.0 m kg, 7.2 ft • • 10 Nm (1.0 m kg, 7.2 ft • • Order Job/Parts to remove Q’ty Remarks Refer to “GENERAL CHASSIS” on page Bottom cowling 4-1.

  • Page 169: Removing The Drive Chain

    CHAIN DRIVE YamahaR125.COM EAS23420 REMOVING THE DRIVE CHAIN 1. Stand the vehicle on a level surface. EWA13120 WARNING Securely support the vehicle so that there is no danger of it falling over. NOTE: Place the vehicle on a suitable stand so that the rear wheel is elevated.

  • Page 170: Checking The Drive Sprocket

    CHAIN DRIVE YamahaR125.COM b. Correct L LLL L LLL L LLL L LLL L LLL 1. Drive chain roller 3. Check: 2. Drive chain sprocket • O-rings “1” Damage → Replace the drive chain. EAS23470 • Drive chain rollers “2” CHECKING THE REAR WHEEL SPROCKET Damage/wear →...
  • Page 171 CHAIN DRIVE YamahaR125.COM NOTE: Install the master link plate with its manufacturer mark facing outward. 4. Install: • Drive sprocket cover NOTE: Be sure not to pinch the neutral switch lead when installing the drive sprocket cover. 5. Install: • Rear wheel Refer to “REAR WHEEL”...
  • Page 172 CHAIN DRIVE YamahaR125.COM 4-67...
  • Page 173 YamahaR125.COM ENGINE ENGINE REMOVAL ..................5-1 INSTALLING THE ENGINE............... 5-5 INSTALLING THE SHIFT ARM ..............5-5 INSTALLING THE EXHAUST ASSEMBLY ..........5-5 CYLINDER HEAD.................... 5-7 REMOVING THE CYLINDER HEAD............5-9 CHECKING THE CYLINDER HEAD ............5-9 CHECKING THE CAMSHAFT SPROCKET AND TIMING CHAIN GUIDE ................
  • Page 174 YamahaR125.COM CLUTCH ......................5-38 REMOVING THE CLUTCH ..............5-42 CHECKING THE FRICTION PLATES............. 5-42 CHECKING THE CLUTCH PLATES ............5-42 CHECKING THE CLUTCH SPRINGS............. 5-43 CHECKING THE CLUTCH HOUSING ............ 5-43 CHECKING THE CLUTCH BOSS............5-43 CHECKING THE PRESSURE PLATE ............ 5-43 CHECKING THE CLUTCH PUSH LEVER AND SHORT CLUTCH PUSH ROD ................
  • Page 175 YamahaR125.COM TRANSMISSION.................... 5-64 CHECKING THE SHIFT FORKS............. 5-67 CHECKING THE SHIFT DRUM ASSEMBLY.......... 5-67 CHECKING THE TRANSMISSION ............5-67 CHECKING THE CLUTCH PUSH RODS ..........5-68 ASSEMBLING THE MAIN AXLE AND DRIVE AXLE ......5-68 INSTALLING THE SHIFT FORKS AND SHIFT DRUM ASSEMBLY ..5-68...

  • Page 176: Engine Removal

    ENGINE REMOVAL YamahaR125.COM EAS23710 ENGINE REMOVAL Removing the exhaust assembly 20 Nm (2.0 m kg, 14 ft • • 20 Nm (2.0 m kg, 14 ft • • Order Job/Parts to remove Q’ty Remarks Refer to “GENERAL CHASSIS” on page Right bottom cowling 4-1.
  • Page 177 ENGINE REMOVAL YamahaR125.COM Disconnecting the leads and couplers 10 Nm (1.0 m kg, 7.2 ft • • 10 Nm (1.0 m kg, 7.2 ft • • Order Job/Parts to remove Q’ty Remarks ECA5D71020 CAUTION: First, disconnect the negative battery lead, then the positive battery lead. Refer to “CHECKING AND CHARGING Negative battery lead/Positive battery lead THE BATTERY”...
  • Page 178 ENGINE REMOVAL YamahaR125.COM Disconnecting the leads and couplers 10 Nm (1.0 m kg, 7.2 ft • • 10 Nm (1.0 m kg, 7.2 ft • • Order Job/Parts to remove Q’ty Remarks Refer to “AIR INDUCTION SYSTEM” on Air induction system reed valve assembly page 7-9.
  • Page 179 ENGINE REMOVAL YamahaR125.COM Removing the engine 46 Nm (4.6 m kg, 33 ft • • 46 Nm (4.6 m kg, 33 ft • • Order Job/Parts to remove Q’ty Remarks NOTE: Place a suitable stand under the engine. Engine mounting bolt/nut (front side) Engine mounting bolt/nut (rear lower side) Engine mounting bolt/nut (rear upper side) Engine...

  • Page 180: Installing The Engine

    ENGINE REMOVAL YamahaR125.COM EAS23720 EAS5D71030 INSTALLING THE ENGINE INSTALLING THE SHIFT ARM 1. Install: 1. Install: • Engine “1” • Shift arm “1” • Engine mounting bolt (rear lower side) “2” NOTE: • Engine mounting nut (rear lower side) “3” Make sure that the distance “a”...
  • Page 181 ENGINE REMOVAL YamahaR125.COM...

  • Page 182: Cylinder Head

    CYLINDER HEAD YamahaR125.COM EAS24100 CYLINDER HEAD Removing the cylinder head 22 Nm (2.2 m kg, 16 ft • • 10 Nm (1.0 m kg, 7.2 ft • • ∗ 13 Nm (1.3 m kg, 9.4 ft • • 10 Nm (1.0 m kg, 7.2 ft •...
  • Page 183 Clutch cable holder Timing chain tensioner Timing chain tensioner gasket Camshaft sprocket Decompression cam Cylinder head Cylinder head gasket Dowel pin Timing chain guide (exhaust side) For installation, reverse the removal proce- dure. * Yamaha bond No. 1215 (Three Bond No. 1215®)

  • Page 184: Removing The Cylinder Head

    CYLINDER HEAD YamahaR125.COM EAS24130 NOTE: REMOVING THE CYLINDER HEAD To prevent the timing chain from falling into the 1. Align: crankcase, fasten it with a wire “1”. • “I” mark “a” on the generator rotor (with the stationary pointer “b” on the genera- tor cover) M MMM M MMM...

  • Page 185: Checking The Camshaft Sprocket And Timing Chain Guide

    CYLINDER HEAD YamahaR125.COM EAS5D71031 CHECKING THE CAMSHAFT SPROCKET AND TIMING CHAIN GUIDE 1. Check: • Camshaft sprocket More than 1/4 tooth wear “a” → Replace the camshaft sprocket, timing chain and crank- shaft as a set. 2. Check: • Cylinder head Damage/scratches →...

  • Page 186: Checking The Decompression System

    CYLINDER HEAD YamahaR125.COM c. Make sure that the timing chain tensioner rod comes out of the timing chain tensioner hous- ing smoothly. If there is rough movement, re- place the timing chain tensioner. L LLL L LLL L LLL L LLL L LLL EAS5D71009 CHECKING THE DECOMPRESSION SYSTEM...
  • Page 187 M MMM M MMM M MMM a. Apply sealant to the timing chain tensioner bolt threads. 3. Install: • Camshaft sprocket Yamaha bond No. 1215 90890-85505 M MMM M MMM M MMM M MMM M MMM a. Turn the crankshaft counterclockwise.
  • Page 188 CYLINDER HEAD YamahaR125.COM 5. Turn: • Crankshaft (several turns counterclockwise) 6. Check: • “I” mark “a” Align the “I” mark on the generator rotor with the stationary pointer “b” on the generator cover. • “I” mark “c” Align the “I” mark on the camshaft sprocket with the stationary pointer “d”...

  • Page 189: Camshaft

    CAMSHAFT YamahaR125.COM EAS23730 CAMSHAFT Removing the rocker arms and camshaft 7 Nm (0.7 m kg, 5.1 ft • • 7 Nm (0.7 m kg, 5.1 ft • • 7 Nm (0.7 m kg, 5.1 ft • • Order Job/Parts to remove Q’ty Remarks Cylinder head...

  • Page 190: Checking The Camshaft

    CAMSHAFT YamahaR125.COM EAS23840 EAS23880 CHECKING THE CAMSHAFT CHECKING THE ROCKER ARMS AND 1. Check: ROCKER ARM SHAFTS • Camshaft lobes The following procedure applies to all of the Blue discoloration/pitting/scratches → Re- rocker arms and rocker arm shafts. place the camshaft. 1.

  • Page 191: Installing The Camshaft And Rocker Arms

    CAMSHAFT YamahaR125.COM 5. Calculate: 4. Install: • Rocker-arm-to-rocker-arm-shaft clearance • Rocker arms • Rocker arm shafts “1” NOTE: NOTE: Calculate the clearance by subtracting the rock- er arm shaft outside diameter from the rocker • Make sure that the cutout “a” in each rocker arm inside diameter.
  • Page 192 VALVES AND VALVE SPRINGS YamahaR125.COM EAS24270 VALVES AND VALVE SPRINGS Removing the valves and valve springs Order Job/Parts to remove Q’ty Remarks Cylinder head Refer to “CYLINDER HEAD” on page 5-7. Rocker arms/Camshaft Refer to “CAMSHAFT” on page 5-14. Valve cotter Upper spring seat Valve spring Intake valve...

  • Page 193: Valves And Valve Springs

    VALVES AND VALVE SPRINGS YamahaR125.COM EAS24280 REMOVING THE VALVES The following procedure applies to all of the valves and related components. NOTE: Before removing the internal parts of the cylinder head (e.g., valves, valve springs, valve seats), make sure the valves properly seal. 1.
  • Page 194 VALVES AND VALVE SPRINGS YamahaR125.COM b. Install the new valve guide with the valve Valve-stem-to-valve-guide clear- guide installer “2” and valve guide remover ance (intake) “1”. 0.010–0.037 mm (0.0004–0.0015 Valve guide position (intake) Limit 17.0–17.4 mm (0.669–0.685 in) 0.080 mm (0.0032 in) Valve guide position (exhaust) Valve-stem-to-valve-guide clear- 14.0–14.4 mm (0.551–0.567 in)

  • Page 195: Checking The Valve Seats

    VALVES AND VALVE SPRINGS YamahaR125.COM 3. Eliminate: EAS24300 CHECKING THE VALVE SEATS • Carbon deposits The following procedure applies to all of the (from the valve face and valve seat) valves and valve seats. 4. Check: 1. Eliminate: • Valve face •...

  • Page 196: Checking The Valve Springs

    VALVES AND VALVE SPRINGS YamahaR125.COM 4. Lap: • Valve face • Valve seat NOTE: After replacing the cylinder head or replacing the valve and valve guide, the valve seat and valve face should be lapped. M MMM M MMM M MMM M MMM M MMM a.

  • Page 197: Installing The Valves

    VALVES AND VALVE SPRINGS YamahaR125.COM Free length (intake) Spring tilt (intake) 41.71 mm (1.64 in) 2.5°/1.8 mm Limit Spring tilt (exhaust) 39.62 mm (1.56 in) 2.5°/1.8 mm Free length (exhaust) 41.71 mm (1.64 in) Limit 39.62 mm (1.56 in) EAS24340 INSTALLING THE VALVES The following procedure applies to all of the valves and related components.
  • Page 198 VALVES AND VALVE SPRINGS YamahaR125.COM • Valve “3” • Valve spring “4” • Upper spring seat “5” (into the cylinder head) NOTE: • Make sure each valve is installed in its original place. • Install the valve springs with the larger pitch “a” facing up.

  • Page 199: Cylinder And Piston

    CYLINDER AND PISTON YamahaR125.COM EAS24350 CYLINDER AND PISTON Removing the cylinder and piston 7 Nm (0.7 m kg, 5.1 ft • • Order Job/Parts to remove Q’ty Remarks Cylinder head Refer to “CYLINDER HEAD” on page 5-7. Cylinder Cylinder gasket Dowel pin Piston pin clip Piston pin...

  • Page 200: Removing The Piston

    CYLINDER AND PISTON YamahaR125.COM EAS24380 NOTE: REMOVING THE PISTON When removing a piston ring, open the end gap 1. Remove: with your fingers and lift the other side of the ring • Piston pin clips “1” over the piston crown. •...

  • Page 201: Checking The Piston Rings

    CYLINDER AND PISTON YamahaR125.COM EAS24430 “C” = maximum of D –D CHECKING THE PISTON RINGS 1. Measure: “T” = maximum of D or D - maximum of D • Piston ring side clearance or D Out of specification → Replace the piston “R”...

  • Page 202: Checking The Piston Pin

    CYLINDER AND PISTON YamahaR125.COM 3. Measure: 3. Measure: • Piston ring end gap • Piston pin bore diameter “b” Out of specification → Replace the piston Out of specification → Replace the piston. ring. Piston pin bore inside diameter NOTE: 14.002–14.013 mm (0.5513–...
  • Page 203 CYLINDER AND PISTON YamahaR125.COM 2. Install: a. Top ring • Piston “1” b. Upper oil ring rail • Piston pin “2” c. Oil ring expander d. Lower oil ring rail • Piston pin clips “3” e. 2nd ring NOTE: f. 20 mm (0.79 in) •...

  • Page 204: Generator And Starter Clutch

    GENERATOR AND STARTER CLUTCH YamahaR125.COM EAS5D71010 GENERATOR AND STARTER CLUTCH Removing the generator and starter clutch 10 Nm (1.0 m kg, 7.2 ft • • 10 Nm (1.0 m kg, 7.2 ft • • 14 Nm (1.4 m kg, 10 ft •...
  • Page 205 GENERATOR AND STARTER CLUTCH YamahaR125.COM Removing the generator and starter clutch 10 Nm (1.0 m kg, 7.2 ft • • 10 Nm (1.0 m kg, 7.2 ft • • 14 Nm (1.4 m kg, 10 ft • • 10 Nm (1.0 m kg, 7.2 ft •...

  • Page 206: Removing The Generator

    GENERATOR AND STARTER CLUTCH YamahaR125.COM EAS24490 REMOVING THE GENERATOR 1. Remove: • Generator rotor nut “1” • Washer NOTE: • While holding the generator rotor “2” with the sheave holder “3”, loosen the generator rotor nut. • Do not allow the sheave holder to touch the projection on the generator rotor.

  • Page 207: Installing The Starter Clutch

    GENERATOR AND STARTER CLUTCH YamahaR125.COM NOTE: • While holding the generator rotor “2” with the sheave holder “3”, tighten the starter clutch bolts. • Do not allow the sheave holder to touch the projection on the generator rotor. • Stake the end “a” of each starter clutch bolt. Sheave holder 90890-01701 2.
  • Page 208 2,10 Primary clutch holder YS-01880-A 3. Apply: • Sealant (onto the crankshaft position sensor/stator assembly lead grommet) Yamaha bond No. 1215 90890-85505 (Three Bond No.1215®) 4. Install: • Generator cover Generator cover bolt 10 Nm (1.0 m·kg, 7.2 ft·lb) NOTE: Tighten the generator cover bolts in the proper tightening sequence as shown.

  • Page 209: Electric Starter

    ELECTRIC STARTER YamahaR125.COM EAS24780 ELECTRIC STARTER Removing the starter motor 10 Nm (1.0 m kg, 7.2 ft • • Order Job/Parts to remove Q’ty Remarks Refer to “GENERAL CHASSIS” on page Lower side cowlings 4-1. Starter motor Starter motor lead Disconnect.
  • Page 210 ELECTRIC STARTER YamahaR125.COM Disassembling the starter motor Order Job/Parts to remove Q’ty Remarks O-ring Starter motor yoke O-ring Commutator Starter motor front cover/brush holder set Brush Brush spring For assembly, reverse the disassembly pro- cedure. 5-35...

  • Page 211: Checking The Starter Motor

    ELECTRIC STARTER YamahaR125.COM EAS24790 CHECKING THE STARTER MOTOR Pocket tester 1. Check: 90890-03112 • Commutator Analog pocket tester Dirt → Clean with 600 grit sandpaper. YU-03112-C 2. Measure: • Commutator diameter “a” Armature coil Out of specification → Replace the starter Commutator resistance “1”...

  • Page 212: Assembling The Starter Motor

    ELECTRIC STARTER YamahaR125.COM 7. Check: • Gear teeth Damage/wear → Replace the gear. 8. Check: • Bearing • Oil seal Damage/wear → Replace the starter motor front cover/brush holder set. EAS24800 ASSEMBLING THE STARTER MOTOR 1. Install: • Starter motor front cover/brush holder set “1” •...

  • Page 213: Clutch

    CLUTCH YamahaR125.COM EAS25061 CLUTCH Removing the clutch cover 10 Nm (1.0 m kg, 7.2 ft • • 10 Nm (1.0 m kg, 7.2 ft • • 10 Nm (1.0 m kg, 7.2 ft • • Order Job/Parts to remove Q’ty Remarks Drain.
  • Page 214 CLUTCH YamahaR125.COM Removing the clutch 70 Nm (7.0 m kg, 50 ft • • 12 Nm (1.2 m kg, 8.7 ft • • 8 Nm (0.8 m kg, 5.8 ft • • Order Job/Parts to remove Q’ty Remarks Locknut Clutch spring Pressure plate Short clutch push rod Clutch push rod holder...
  • Page 215 CLUTCH YamahaR125.COM Removing the clutch 70 Nm (7.0 m kg, 50 ft • • 12 Nm (1.2 m kg, 8.7 ft • • 8 Nm (0.8 m kg, 5.8 ft • • Order Job/Parts to remove Q’ty Remarks Conical spring washer For installation, reverse the removal proce- dure.
  • Page 216 CLUTCH YamahaR125.COM Removing the push lever Order Job/Parts to remove Q’ty Remarks Clutch push lever Clutch push lever spring Circlip Oil seal Bearing For installation, reverse the removal proce- dure. 5-41...

  • Page 217: Removing The Clutch

    CLUTCH YamahaR125.COM EAS25070 REMOVING THE CLUTCH 1. Straighten the lock washer tab. 2. Loosen: • Clutch boss nut “1” NOTE: While holding the clutch boss “2” with the univer- sal clutch holder “3”, loosen the clutch boss nut. Universal clutch holder 90890-04086 YM-91042 EAS25100...

  • Page 218: Checking The Clutch Springs

    CLUTCH YamahaR125.COM Clutch plate thickness 1.45–1.75 mm (0.057–0.069 in) Warpage limit 0.20 mm (0.0079 in) 2. Check: • Bearing Damage/wear → Replace the bearing and clutch housing. EAS25160 CHECKING THE CLUTCH BOSS EAS25140 CHECKING THE CLUTCH SPRINGS 1. Check: The following procedure applies to all of the •...

  • Page 219: Checking The Primary Driven Gear

    CLUTCH YamahaR125.COM 2. Check: NOTE: • Primary drive gear Be sure to install the thrust washer so that its Damage/wear → Replace the primary drive sharp edge “a” is facing away from the clutch gear and clutch housing as a set. boss.
  • Page 220 CLUTCH YamahaR125.COM NOTE: Tighten the clutch spring bolts in stages and in a crisscross pattern. 5. Bend the lock washer tab along a flat side of the nut. 6. Lubricate: • Friction plates 9. Adjust: • Clutch plates • Clutch mechanism free play (with the recommended lubricant) M MMM M MMM...
  • Page 221 CLUTCH YamahaR125.COM L LLL L LLL L LLL L LLL L LLL 10.Install: • Oil seal “1” Installed depth of oil seal “a” 1.4–1.9 mm (0.055–0.075 in) 11.Install: • Clutch cover Clutch cover bolt 10 Nm (1.0 m·kg, 7.2 ft·lb) NOTE: Tighten the clutch cover bolts in the proper tight- ening sequence as shown.

  • Page 222: Oil Pump

    OIL PUMP YamahaR125.COM EAS24911 OIL PUMP Removing the oil pump 4 Nm (0.4 m kg, 2.9 ft • • 10 Nm (1.0 m kg, 7.2 ft • • Order Job/Parts to remove Q’ty Remarks Clutch housing Refer to “CLUTCH” on page 5-38. Balancer drive gear Refer to “BALANCER GEAR”...
  • Page 223 OIL PUMP YamahaR125.COM Disassembling the oil pump Order Job/Parts to remove Q’ty Remarks Oil pump housing cover Oil pump driven gear Oil pump inner rotor Oil pump outer rotor Oil pump housing For assembly, reverse the disassembly pro- cedure. 5-48...

  • Page 224: Checking The Oil Pump

    OIL PUMP YamahaR125.COM EAS24960 CHECKING THE OIL PUMP Inner-rotor-to-outer-rotor-tip 1. Check: clearance • Oil pump drive gear Less than 0.15 mm (0.0059 in) • Oil pump driven gear Limit 0.23 mm (0.0091 in) • Oil pump housing Outer-rotor-to-oil-pump-housing • Oil pump housing cover clearance Cracks/damage/wear →...

  • Page 225: Installing The Oil Pump

    OIL PUMP YamahaR125.COM 3. Check: • Oil pump operation Refer to “CHECKING THE OIL PUMP” on page 5-49. EAS25020 INSTALLING THE OIL PUMP 1. Install: • Oil pump assembly Oil pump assembly screw 4 Nm (0.4 m·kg, 2.9 ft·lb) ECA5D71021 CAUTION: After tightening the screws, make sure the oil pump turns smoothly.

  • Page 226: Shift Shaft

    SHIFT SHAFT YamahaR125.COM EAS25410 SHIFT SHAFT Removing the shift shaft and stopper lever 10 Nm (1.0 m kg, 7.2 ft • • Order Job/Parts to remove Q’ty Remarks Clutch housing Refer to “CLUTCH” on page 5-38. Shift arm Refer to “ENGINE REMOVAL” on page 5-1. Shift shaft Circlip Shift shaft spring...

  • Page 227: Checking The Shift Shaft

    SHIFT SHAFT YamahaR125.COM EAS25420 CHECKING THE SHIFT SHAFT 1. Check: • Shift shaft Bends/damage/wear → Replace. • Shift shaft spring Damage/wear → Replace. EAS25430 CHECKING THE STOPPER LEVER 1. Check: • Stopper lever Bends/damage → Replace. Roller turns roughly → Replace the stopper lever.

  • Page 228: Balancer Gear

    BALANCER GEAR YamahaR125.COM EAS5D71017 BALANCER GEAR Removing the primary drive gear and balancer gears 60 Nm (6.0 m kg, 43 ft • • 50 Nm (5.0 m kg, 36 ft • • Order Job/Parts to remove Q’ty Remarks Clutch housing Refer to “CLUTCH”...

  • Page 229: Removing The Primary Drive Gear And Balancer Gears

    BALANCER GEAR YamahaR125.COM EAS5D71018 EAS5D71021 REMOVING THE PRIMARY DRIVE GEAR INSTALLING THE PRIMARY DRIVE GEAR AND BALANCER GEARS AND BALANCER GEARS 1. Loosen: 1. Install: • Primary drive gear nut “1” • Balancer driven gear “1” NOTE: • Lock washer Place the aluminum plate “a”...
  • Page 230 BALANCER GEAR YamahaR125.COM • Place the aluminum plate “b” between the bal- ancer drive gear “3” and the balancer driven gear “4”, and then tighten the primary drive gear nut. 3. Bend the lock washer tab along a flat side of the nut.

  • Page 231: Crankcase

    CRANKCASE YamahaR125.COM EAS25540 CRANKCASE Separating the crankcase 10 Nm (1.0 m kg, 7.2 ft • • 10 Nm (1.0 m kg, 7.2 ft • • 32 Nm (3.2 m kg, 23 ft • • 20 Nm (2.0 m kg, 14 ft •...
  • Page 232 CRANKCASE YamahaR125.COM Separating the crankcase 10 Nm (1.0 m kg, 7.2 ft • • 10 Nm (1.0 m kg, 7.2 ft • • 32 Nm (3.2 m kg, 23 ft • • 20 Nm (2.0 m kg, 14 ft • •...
  • Page 233 CRANKCASE YamahaR125.COM Removing the oil seal and bearings 7 Nm (0.7 m kg, 5.1 ft • • Order Job/Parts to remove Q’ty Remarks Crankshaft/Balancer Refer to “CRANKSHAFT” on page 5-61. Transmission Refer to “TRANSMISSION” on page 5-64. Oil seal Bearing retainer Bearing For installation, reverse the removal proce- dure.

  • Page 234: Separating The Crankcase

    CRANKCASE YamahaR125.COM EAS5D71032 ECA13900 SEPARATING THE CRANKCASE CAUTION: 1. Remove: Tap on one side of the crankcase with a soft- • Crankcase bolts face hammer. Tap only on reinforced por- NOTE: tions of the crankcase, not on the crankcase Loosen each bolt 1/4 of a turn at a time, in stag- mating surfaces.

  • Page 235: Installing The Bearing Retainer

    1. Thoroughly clean all the gasket mating sur- • M6 × 45 mm : “1–5”, “10” faces and crankcase mating surfaces. 2. Apply: • Sealant (onto the crankcase mating surfaces) Yamaha bond No. 1215 90890-85505 2,12 (Three Bond No.1215®) NOTE: 3,13 Do not allow any sealant to come into contact with the oil gallery.

  • Page 236: Crankshaft

    CRANKSHAFT YamahaR125.COM EAS25960 CRANKSHAFT Removing the crankshaft and balancer Order Job/Parts to remove Q’ty Remarks Separate. Crankcase Refer to “CRANKCASE” on page 5-56. Balancer Crankshaft For installation, reverse the removal proce- dure. 5-61...

  • Page 237: Removing The Crankshaft

    CRANKSHAFT YamahaR125.COM EAS5D71016 REMOVING THE CRANKSHAFT 1. Remove: • Crankshaft “1” NOTE: • Remove the crankshaft with the crankcase separating tool “2”. • Make sure the crankcase separating tool is centered over the crankshaft. ECA5D71022 2. Measure: CAUTION: • Big end side clearance •...
  • Page 238 CRANKSHAFT YamahaR125.COM Crankshaft installer pot 90890-01274 Installing pot YU-90058 Crankshaft installer bolt 90890-01275 Bolt YU-90060 Adapter (M12) 90890-01278 Adapter #3 YU-90063 Spacer (crankshaft installer) 90890-04081 Pot spacer YM-91044 ECA13970 CAUTION: To avoid scratching the crankshaft and to ease the installation procedure, lubricate the oil seal lips with lithium-soap-based grease and each bearing with engine oil.

  • Page 239: Transmission

    TRANSMISSION YamahaR125.COM EAS26241 TRANSMISSION Removing the transmission, shift drum assembly, and shift forks Order Job/Parts to remove Q’ty Remarks Separate. Crankcase Refer to “CRANKCASE” on page 5-56. Shift fork guide bar Spring Shift drum assembly Shift fork-R Shift fork-C Shift fork-L Drive axle assembly Main axle assembly Long clutch push rod...
  • Page 240 TRANSMISSION YamahaR125.COM Disassembling the main axle Order Job/Parts to remove Q’ty Remarks 2nd pinion gear 6th pinion gear 3rd/4th pinion gear Circlip Toothed washer 5th pinion gear Main axle/1st pinion gear For assembly, reverse the disassembly pro- cedure. 5-65...
  • Page 241 TRANSMISSION YamahaR125.COM Disassembling the drive axle Order Job/Parts to remove Q’ty Remarks Washer 2nd wheel gear 6th wheel gear Washer 1st wheel gear Spacer 5th wheel gear Circlip Toothed washer 4th wheel gear 3rd wheel gear Drive axle For assembly, reverse the disassembly pro- cedure.

  • Page 242: Checking The Shift Forks

    TRANSMISSION YamahaR125.COM EAS26260 EAS26270 CHECKING THE SHIFT FORKS CHECKING THE SHIFT DRUM ASSEMBLY The following procedure applies to all of the shift 1. Check: forks. • Shift drum groove Damage/scratches/wear → Replace the shift 1. Check: • Shift fork cam follower “1” drum assembly.

  • Page 243: Checking The Clutch Push Rods

    TRANSMISSION YamahaR125.COM EAS29020 ASSEMBLING THE MAIN AXLE AND DRIVE AXLE 1. Install: • Toothed washer “1” • Circlip “2” NOTE: • Be sure to install the circlip so that its sharp edge “a” is facing away from the toothed wash- er and gear.
  • Page 244 TRANSMISSION YamahaR125.COM NOTE: The embossed marks on the shift forks should face towards the right side of the engine and be in the following sequence: “R”, “C”, “L”. 2. Check: • Transmission Rough movement → Repair. NOTE: • Apply engine oil to each gear and bearing thor- oughly.
  • Page 245 YamahaR125.COM COOLING SYSTEM RADIATOR ...................... 6-1 CHECKING THE RADIATOR..............6-3 INSTALLING THE RADIATOR..............6-3 THERMOSTAT ....................6-4 CHECKING THE THERMOSTAT.............. 6-5 INSTALLING THE THERMOSTAT............6-5 WATER PUMP....................6-6 DISASSEMBLING THE WATER PUMP............ 6-8 CHECKING THE WATER PUMP .............. 6-8 ASSEMBLING THE WATER PUMP............6-8 INSTALLING THE WATER PUMP ............

  • Page 246: Radiator

    RADIATOR YamahaR125.COM EAS26380 RADIATOR Removing the radiator 8 Nm (0.8 m kg, 5.8 ft • • 7 Nm (0.7 m kg, 5.1 ft • • 10 Nm (1.0 m kg, 7.2 ft • • Order Job/Parts to remove Q’ty Remarks Drain.
  • Page 247 RADIATOR YamahaR125.COM Removing the radiator 8 Nm (0.8 m kg, 5.8 ft • • 7 Nm (0.7 m kg, 5.1 ft • • 10 Nm (1.0 m kg, 7.2 ft • • Order Job/Parts to remove Q’ty Remarks Radiator cover For installation, reverse the removal proce- dure.

  • Page 248: Checking The Radiator

    RADIATOR YamahaR125.COM EAS26390 CHECKING THE RADIATOR 1. Check: • Radiator fins Obstruction → Clean. Apply compressed air to the rear of the radia- tor. Damage → Repair or replace. NOTE: Straighten any flattened fins with a thin, flat-head screwdriver. b. Apply the specified pressure for ten seconds and make sure there is no drop in pressure.

  • Page 249: Thermostat

    THERMOSTAT YamahaR125.COM EAS26440 THERMOSTAT Removing the thermostat 18 Nm (1.8 m kg, 13 ft • • 10 Nm (1.0 m kg, 7.2 ft • • Order Job/Parts to remove Q’ty Remarks Drain. Coolant Refer to “CHANGING THE COOLANT” on page 3-15. Refer to “GENERAL CHASSIS”...

  • Page 250: Checking The Thermostat

    THERMOSTAT YamahaR125.COM 2. Check: EAS26450 CHECKING THE THERMOSTAT • Thermostat cover 1. Check: Cracks/damage → Replace. • Thermostat 3. Check: Does not open at 80.5–83.5 °C (176.9–182.3 • Radiator inlet hose °F) → Replace. Cracks/damage → Replace. EAS26480 INSTALLING THE THERMOSTAT 1.

  • Page 251: Water Pump

    WATER PUMP YamahaR125.COM EAS26500 WATER PUMP Removing the water pump 10 Nm (1.0 m kg, 7.2 ft • • 10 Nm (1.0 m kg, 7.2 ft • • Order Job/Parts to remove Q’ty Remarks It is not necessary to remove the water pump unless the coolant level is extremely low or the coolant contains engine oil.
  • Page 252 WATER PUMP YamahaR125.COM Disassembling the water pump 10 Nm (1.0 m kg, 7.2 ft • • 10 Nm (1.0 m kg, 7.2 ft • • 10 Nm (1.0 m kg, 7.2 ft • • Order Job/Parts to remove Q’ty Remarks Radiator bracket Water pump housing cover Water pump housing cover gasket...

  • Page 253: Disassembling The Water Pump

    WATER PUMP YamahaR125.COM EAS26510 ECA14080 DISASSEMBLING THE WATER PUMP CAUTION: 1. Remove: Never lubricate the water pump seal surface • Water pump seal “1” with oil or grease. NOTE: NOTE: Remove the water pump seal from the inside of • Install the water pump seal with the special the water pump housing “2”.

  • Page 254: Installing The Water Pump

    WATER PUMP YamahaR125.COM • Water pump housing plate “2” Refer to “CHANGING THE COOLANT” on • Impeller shaft page 3-15. • Impeller shaft retainer “3” 3. Check: • Cooling system Impeller shaft retainer bolt Leaks → Repair or replace the faulty part. 10 Nm (1.0 m·kg, 7.2 ft·lb) 4.
  • Page 255 YamahaR125.COM FUEL SYSTEM FUEL TANK..................... 7-1 REMOVING THE FUEL TANK ..............7-2 CHECKING THE FUEL PUMP BODY............7-2 INSTALLING THE FUEL HOSE ..............7-2 CHECKING THE FUEL PRESSURE ............7-2 THROTTLE BODY................... 7-4 REMOVING THE THROTTLE BODY............7-6 CHECKING THE FUEL INJECTOR ............7-6 CHECKING THE THROTTLE BODY ............

  • Page 256: Fuel Tank

    FUEL TANK YamahaR125.COM EAS26620 FUEL TANK Removing the fuel tank 10 Nm (1.0 m kg, 7.2 ft • • 10 Nm (1.0 m kg, 7.2 ft • • Order Job/Parts to remove Q’ty Remarks Refer to “GENERAL CHASSIS” on page Fuel tank cover 4-1.

  • Page 257: Removing The Fuel Tank

    FUEL TANK YamahaR125.COM EAS26630 ECA5D71032 REMOVING THE FUEL TANK CAUTION: 1. Extract the fuel in the fuel tank through the When installing the fuel hose, make sure that fuel tank filler hole with a pump. it is securely connected, and that the fuel 2.
  • Page 258 FUEL TANK YamahaR125.COM b. Connect the pressure gauge “3” and fuel pressure adapter “4”. Pressure gauge 90890-03153 YU-03153 Fuel pressure adapter 90890-03181 c. Start the engine. d. Measure the fuel pressure. Output pressure 250.0 kPa (36.3 psi) (2.50 kgf/cm²) Faulty → Replace the fuel tank (with fuel pump).

  • Page 259: Throttle Body

    THROTTLE BODY YamahaR125.COM EAS26970 THROTTLE BODY Removing the throttle body 12 Nm (1.2 m kg, 8.7 ft • • 7 Nm (0.7 m kg, 5.1 ft • • 10 Nm (1.0 m kg, 7.2 ft • • 2 Nm (0.2 m kg, 1.4 ft •...
  • Page 260 THROTTLE BODY YamahaR125.COM Removing the throttle body 12 Nm (1.2 m kg, 8.7 ft • • 7 Nm (0.7 m kg, 5.1 ft • • 10 Nm (1.0 m kg, 7.2 ft • • 2 Nm (0.2 m kg, 1.4 ft •...

  • Page 261: Removing The Throttle Body

    THROTTLE BODY YamahaR125.COM EAS5D71025 EAS5D71028 REMOVING THE THROTTLE BODY CHECKING THE FUEL INJECTOR 1. Extract the fuel in the fuel tank through the 1. Check: fuel tank filler hole with a pump. • Fuel injector Damage → Replace. 2. Disconnect: •...
  • Page 262 THROTTLE BODY YamahaR125.COM 3. Install: • Throttle body NOTE: Align the projection “a” on the throttle body with the slot “b” in the throttle body joint. 4. Adjust: • Throttle cable free play Refer to “ADJUSTING THE THROTTLE CA- BLE FREE PLAY” on page 3-6. 5.
  • Page 263 THROTTLE BODY YamahaR125.COM...

  • Page 264: Air Induction System

    AIR INDUCTION SYSTEM YamahaR125.COM EAS27040 AIR INDUCTION SYSTEM...
  • Page 265 AIR INDUCTION SYSTEM YamahaR125.COM 1. Air induction system hose (air filter case to reed valve assembly) 2. Air induction system reed valve assembly 3. Air induction system hose (reed valve assembly to exhaust pipe) 7-10...
  • Page 266 AIR INDUCTION SYSTEM YamahaR125.COM Removing the air induction system reed valve assembly 10 Nm (1.0 m kg, 7.2 ft • • Order Job/Parts to remove Q’ty Remarks Refer to “GENERAL CHASSIS” on page Rider seat/Right side cover 4-1. Fuel tank Refer to “FUEL TANK”...

  • Page 267: Checking The Air Induction System

    AIR INDUCTION SYSTEM YamahaR125.COM EAS27060 CHECKING THE AIR INDUCTION SYSTEM Air injection The air induction system burns unburned ex- haust gases by injecting fresh air (secondary air) into the exhaust port, reducing the emission of hydrocarbons. When there is negative pressure at the exhaust port, the reed valve opens, allow- ing secondary air to flow into the exhaust port.
  • Page 268 AIR INDUCTION SYSTEM YamahaR125.COM 7-13...
  • Page 269 YamahaR125.COM ELECTRICAL SYSTEM IGNITION SYSTEM ..................8-1 CIRCUIT DIAGRAM .................. 8-1 TROUBLESHOOTING ................8-3 ELECTRIC STARTING SYSTEM ..............8-5 CIRCUIT DIAGRAM .................. 8-5 STARTING CIRCUIT CUT-OFF SYSTEM OPERATION ......8-7 TROUBLESHOOTING ................8-9 CHARGING SYSTEM..................8-11 CIRCUIT DIAGRAM ................8-11 TROUBLESHOOTING ................
  • Page 270 YamahaR125.COM ELECTRICAL COMPONENTS..............8-57 CHECKING THE SWITCHES ..............8-59 CHECKING THE BULBS AND BULB SOCKETS ........8-62 CHECKING THE FUSES ................ 8-63 CHECKING AND CHARGING THE BATTERY........8-64 CHECKING THE RELAYS ..............8-66 CHECKING THE TURN SIGNAL RELAY ..........8-66 CHECKING THE DIODE .................
  • Page 271 YamahaR125.COM...

  • Page 272: Ignition System

    IGNITION SYSTEM YamahaR125.COM EAS27090 IGNITION SYSTEM EAS27100 CIRCUIT DIAGRAM...
  • Page 273 IGNITION SYSTEM YamahaR125.COM 2. Crankshaft position sensor 4. Main fuse 5. Main switch 8. Sidestand switch 9. Battery 17.Engine stop switch 23.Lean angle sensor 25.ECU (engine control unit) 26.Ignition coil 27.Spark plug 64.Ignition fuse...

  • Page 274: Troubleshooting

    IGNITION SYSTEM YamahaR125.COM EAS27120 TROUBLESHOOTING The ignition system fails to operate (no spark or intermittent spark). NOTE: • Before troubleshooting, remove the following part(s): 1. Seats 2. Fuel tank 3. Right side cover 4. Left side panel 5. Left upper side cowling NG →...
  • Page 275 IGNITION SYSTEM YamahaR125.COM NG → 8. Check the main switch. Refer to “CHECKING THE Replace the main switch. SWITCHES” on page 8-59. OK ↓ NG → 9. Check the engine stop switch. The engine stop switch is faulty. Replace Refer to “CHECKING THE the right handlebar switch.

  • Page 276: Electric Starting System

    ELECTRIC STARTING SYSTEM YamahaR125.COM EAS27160 ELECTRIC STARTING SYSTEM EAS27170 CIRCUIT DIAGRAM...
  • Page 277 ELECTRIC STARTING SYSTEM YamahaR125.COM 4. Main fuse 5. Main switch 7. Clutch switch 8. Sidestand switch 9. Battery 10.Starter relay 11.Starter motor 12.Starting circuit cut-off relay 13.Diode 14.Neutral switch 16.Start switch 17.Engine stop switch 64.Ignition fuse...

  • Page 278: Starting Circuit Cut-Off System Operation

    ELECTRIC STARTING SYSTEM YamahaR125.COM EAS27180 STARTING CIRCUIT CUT-OFF SYSTEM OPERATION If the engine stop switch is set to “ ” and the main switch is set to “ON” (both switches are closed), the starter motor can only operate if at least one of the following conditions is met: •...
  • Page 279 ELECTRIC STARTING SYSTEM YamahaR125.COM a. WHEN THE TRANSMISSION IS IN NEUTRAL b. WHEN CLUTCH LEVER IS PULLED TO THE HANDLEBAR AND THE SIDESTAND IS UP 1. Battery 2. Main fuse 3. Main switch 4. Ignition fuse 5. Engine stop switch 6.

  • Page 280: Troubleshooting

    ELECTRIC STARTING SYSTEM YamahaR125.COM EAS27190 TROUBLESHOOTING The starter motor fails to turn. NOTE: • Before troubleshooting, remove the following part(s): 1. Seats 2. Fuel tank 3. Left lower side cowling 4. Left upper side cowling NG → 1. Check the fuses. (Main and ignition) Replace the fuse(s).
  • Page 281 ELECTRIC STARTING SYSTEM YamahaR125.COM NG → 8. Check the main switch. Refer to “CHECKING THE Replace the main switch. SWITCHES” on page 8-59. OK ↓ NG → 9. Check the engine stop switch. The engine stop switch is faulty. Replace Refer to “CHECKING THE the right handlebar switch.

  • Page 282: Charging System

    CHARGING SYSTEM YamahaR125.COM EAS27200 CHARGING SYSTEM EAS27210 CIRCUIT DIAGRAM 8-11...
  • Page 283 CHARGING SYSTEM YamahaR125.COM 1. AC magneto 3. Rectifier/regulator 4. Main fuse 9. Battery 8-12...

  • Page 284: Troubleshooting

    CHARGING SYSTEM YamahaR125.COM EAS27230 TROUBLESHOOTING The battery is not being charged. NOTE: • Before troubleshooting, remove the following part(s): 1. Rider seat 2. Left side panel 3. Left lower side cowling NG → 1. Check the fuse. (Main) Replace the fuse. Refer to “CHECKING THE FUS- ES”...
  • Page 285 CHARGING SYSTEM YamahaR125.COM 8-14...

  • Page 286: Lighting System

    LIGHTING SYSTEM YamahaR125.COM EAS27240 LIGHTING SYSTEM EAS27250 CIRCUIT DIAGRAM 8-15...
  • Page 287 LIGHTING SYSTEM YamahaR125.COM 4. Main fuse 5. Main switch 9. Battery 25.ECU (engine control unit) 36.License plate light 37.Tail/brake light 44.Headlight relay 46.Pass switch 47.Dimmer switch 51.Headlight (low beam) 52.Auxiliary light 54.Headlight (high beam) 58.Meter light 60.High beam indicator light 64.Ignition fuse 65.Headlight fuse 66.Signaling system fuse...

  • Page 288: Troubleshooting

    LIGHTING SYSTEM YamahaR125.COM EAS27260 TROUBLESHOOTING Any of the following fail to light: headlight, high beam indicator light, taillight, license plate light, auxiliary light or meter light. NOTE: • Before troubleshooting, remove the following part(s): 1. Seats 2. Fuel tank NG → 1.
  • Page 289 LIGHTING SYSTEM YamahaR125.COM NG → 8. Check the entire lighting system wiring. Properly connect or repair the lighting sys- Refer to “CIRCUIT DIAGRAM” on tem wiring. page 8-15. OK ↓ Replace the ECU or meter assembly. 8-18...

  • Page 290: Signaling System

    SIGNALING SYSTEM YamahaR125.COM EAS27270 SIGNALING SYSTEM EAS27280 CIRCUIT DIAGRAM 8-19...
  • Page 291 SIGNALING SYSTEM YamahaR125.COM 4. Main fuse 5. Main switch 9. Battery 14.Neutral switch 25.ECU (engine control unit) 31.Fuel sender 34.Rear brake light switch 35.Front brake light switch 37.Tail/brake light 38.Rear right turn signal light 39.Rear left turn signal light 40.Front right turn signal light 41.Front left turn signal light 42.Turn signal relay 43.Horn...

  • Page 292: Troubleshooting

    SIGNALING SYSTEM YamahaR125.COM EAS27290 TROUBLESHOOTING • Any of the following fail to light: turn signal lights, brake light or indicator lights. • The horn fails to sound. • The fuel gauge fails to operate. • The speedometer fails to operate. NOTE: •...
  • Page 293 SIGNALING SYSTEM YamahaR125.COM NG → 2. Check the horn. Refer to “CHECKING THE HORN” Replace the horn. on page 8-71. OK ↓ NG → 3. Check the entire signaling system wiring. Properly connect or repair the signaling Refer to “CIRCUIT DIAGRAM” on system wiring.
  • Page 294 SIGNALING SYSTEM YamahaR125.COM NG → 4. Check the entire signaling system wiring. Properly connect or repair the signaling Refer to “CIRCUIT DIAGRAM” on system wiring. page 8-19. OK ↓ Replace the meter assembly. The neutral indicator light fails to come on. NG →...
  • Page 295 SIGNALING SYSTEM YamahaR125.COM 8-24...

  • Page 296: Cooling System

    COOLING SYSTEM YamahaR125.COM EAS27300 COOLING SYSTEM EAS27310 CIRCUIT DIAGRAM 8-25...
  • Page 297 COOLING SYSTEM YamahaR125.COM 4. Main fuse 5. Main switch 6. Radiator fan motor fuse 9. Battery 22.Coolant temperature sensor 25.ECU (engine control unit) 32.Radiator fan motor relay 33.Radiator fan motor 59.Coolant temperature warning light 64.Ignition fuse 66.Signaling system fuse 8-26...

  • Page 298: Troubleshooting

    COOLING SYSTEM YamahaR125.COM EAS27320 TROUBLESHOOTING NOTE: • Before troubleshooting, remove the following part(s): 1. Rider seat 2. Fuel tank 3. Right upper side cowling 4. Passenger seat NG → 1. Check the fuses. (Main, ignition, and signaling sys- tem) Replace the fuse(s). Refer to “CHECKING THE FUS- ES”...
  • Page 299 COOLING SYSTEM YamahaR125.COM 8-28...

  • Page 300: Fuel Injection System

    FUEL INJECTION SYSTEM YamahaR125.COM EAS27330 FUEL INJECTION SYSTEM EAS27340 CIRCUIT DIAGRAM 8-29...
  • Page 301 FUEL INJECTION SYSTEM YamahaR125.COM 2. Crankshaft position sensor 4. Main fuse 5. Main switch 6. Radiator fan motor fuse 8. Sidestand switch 9. Battery 17.Engine stop switch 19.Intake air pressure sensor 20.Intake air temperature sensor 21.Throttle position sensor 22.Coolant temperature sensor 23.Lean angle sensor 24.Self-diagnosis signal connector 25.ECU (engine control unit)

  • Page 302: Ecu Self-Diagnostic Function

    FUEL INJECTION SYSTEM YamahaR125.COM EAS27350 ECU SELF-DIAGNOSTIC FUNCTION The ECU is equipped with a self-diagnostic function in order to ensure that the fuel injection system is operating normally. If this function detects a malfunction in the system, it immediately operates the en- gine under substitute characteristics and illuminates the engine trouble warning light to alert the rider that a malfunction has occurred in the system.

  • Page 303: Self-Diagnostic Function Table

    FUEL INJECTION SYSTEM YamahaR125.COM Engine trouble warning light indication and fuel injection system operation Warning light indica- Fuel injection opera- ECU operation Vehicle operation tion tion Warning provided Flashing* when unable to start Operation stopped Cannot be operated engine Operated with substi- tute characteristics in Can or cannot be oper- Remains on...
  • Page 304 FUEL INJECTION SYSTEM YamahaR125.COM Self-Diagnostic Function table Able / un- Fault Able / un- Item Symptom able to code No. able to start drive No normal signals are received Crankshaft position from the crankshaft position sen- Unable Unable sensor sor. Intake air pressure Intake air pressure sensor: open sensor...

  • Page 305: Troubleshooting Method

    FUEL INJECTION SYSTEM YamahaR125.COM The engine operation is not normal but the EAS27400 TROUBLESHOOTING METHOD engine trouble warning light does not come The engine operation is not normal and the 1. Check the operation of the following sensors engine trouble warning light comes on. and actuators in the diagnostic mode.

  • Page 306: Diagnostic Mode

    FUEL INJECTION SYSTEM YamahaR125.COM EAS27431 DIAGNOSTIC MODE It is possible to monitor the sensor output data or check the activation of actuators with the FI diagnostic tool connected to the vehicle and set to the normal mode or the diagnostic monitoring mode. FI diagnostic tool 90890-03182 Setting the normal mode...
  • Page 307 FUEL INJECTION SYSTEM YamahaR125.COM 5. Set the main switch to “OFF” to cancel the normal mode. 6. Disconnect the FI diagnostic tool and connect the self-diagnosis signal connector. Setting the diagnostic mode 1. Set the main switch to “OFF” and the engine stop switch to “ ”.
  • Page 308 FUEL INJECTION SYSTEM YamahaR125.COM 9. Set the main switch to “OFF” to cancel the diagnostic mode. 10.Disconnect the FI diagnostic tool and connect the self-diagnosis signal connector. Diagnostic code table Fault Diagnostic code Symptom Probable cause of malfunction code No. •...
  • Page 309 FUEL INJECTION SYSTEM YamahaR125.COM Fault Diagnostic code Symptom Probable cause of malfunction code No. • Open or short circuit in wire harness. No normal signals are re- • Defective speed sensor. ceived from the speed sen- • Malfunction in vehicle speed sensor detect- sor.
  • Page 310 FUEL INJECTION SYSTEM YamahaR125.COM Diag- nostic Item FI diagnostic tool display Checking method code Lean angle sensor Remove the lean angle sensor and incline it more • Upright 0.4–1.4 than 65 degrees. • Overturned 3.7–4.4 Fuel system voltage 0–18.7 Compare with the actually (battery voltage) Approximately 12.0 measured battery voltage.
  • Page 311 FUEL INJECTION SYSTEM YamahaR125.COM Actuator operation table Diag- nostic Item Actuation Checking method code When the “MODE” button is pressed, the ignition coil is actuated five times at one- Check the spark five times. Ignition coil second intervals. • Connect an ignition Illuminates the “WARNING”...

  • Page 312: Troubleshooting Details

    FUEL INJECTION SYSTEM YamahaR125.COM EAS27471 TROUBLESHOOTING DETAILS This section describes the measures per fault code number displayed on the FI diagnostic tool. Check and service the items or components that are the probable cause of the malfunction following the order given.
  • Page 313 FUEL INJECTION SYSTEM YamahaR125.COM Fault code No. Symptom Intake air pressure sensor: open or short circuit detected. Diagnostic code No. Intake air pressure sensor Order Item/components and probable Check or maintenance job Reinstatement cause method Connections • Check the coupler for any pins Setting the •...
  • Page 314 FUEL INJECTION SYSTEM YamahaR125.COM Fault code No. Symptom Intake air pressure sensor: system malfunction (clogged hole). Diagnostic code No. Intake air pressure sensor Order Item/components and probable Check or maintenance job Reinstatement cause method Connections • Check the coupler for any pins Starting the en- •...
  • Page 315 FUEL INJECTION SYSTEM YamahaR125.COM Fault code No. Symptom Throttle position sensor: open or short circuit detected. Diagnostic code No. Throttle position sensor Order Item/components and probable Check or maintenance job Reinstatement cause method Connections • Check the coupler for any pins Setting the •...

  • Page 316: Fault Code 16/19

    FUEL INJECTION SYSTEM YamahaR125.COM Fault code No. Symptom Throttle position sensor is stuck. Diagnostic code No. Throttle position sensor Order Item/components and probable Check or maintenance job Reinstatement cause method Defective throttle position sensor. • Execute the diagnostic mode. Starting the en- (Code No.01) gine, operating •...
  • Page 317 FUEL INJECTION SYSTEM YamahaR125.COM Fault code No. Symptom Coolant temperature sensor: open or short circuit detect- Diagnostic code No. Coolant temperature sensor Order Item/components and probable Check or maintenance job Reinstatement cause method Installed condition of coolant tempera- Check the installed area for Setting the ture sensor looseness or pinching.
  • Page 318 FUEL INJECTION SYSTEM YamahaR125.COM Fault code No. Symptom Intake air temperature sensor: open or short circuit de- tected. Diagnostic code No. Intake air temperature sensor Order Item/components and probable Check or maintenance job Reinstatement cause method Connections • Check the couplers for any pins Setting the •...
  • Page 319 FUEL INJECTION SYSTEM YamahaR125.COM Fault code No. Symptom No normal signal is received from the lean angle sensor. Diagnostic code No. Lean angle sensor Order Item/components and probable Check or maintenance job Reinstatement cause method The vehicle has overturned. Raise the vehicle upright. Setting the main switch to Installed condition of the lean angle...
  • Page 320 FUEL INJECTION SYSTEM YamahaR125.COM Fault code No. Symptom Fuel injector: open or short circuit detected. Diagnostic code No. Fuel injector Order Item/components and probable Check or maintenance job Reinstatement cause method Connections • Check the couplers for any pins Cranking the •...
  • Page 321 FUEL INJECTION SYSTEM YamahaR125.COM Fault code No. Symptom No normal signals are received from the speed sensor. Diagnostic code No. Speed sensor Order Item/components and probable Check or maintenance job Reinstatement cause method Connections • Check the coupler for any pins Start the en- •...
  • Page 322 FUEL INJECTION SYSTEM YamahaR125.COM Fault code No. Symptom Power supply to the fuel injection system is not normal. Diagnostic code No. — — Order Item/components and probable Check or maintenance job Reinstatement cause method Connections • Check the coupler for any pins Starting the en- •...
  • Page 323 FUEL INJECTION SYSTEM YamahaR125.COM 8-52...

  • Page 324: Fuel Pump System

    FUEL PUMP SYSTEM YamahaR125.COM EAS27550 FUEL PUMP SYSTEM EAS27560 CIRCUIT DIAGRAM 8-53...
  • Page 325 FUEL PUMP SYSTEM YamahaR125.COM 4. Main fuse 5. Main switch 9. Battery 17.Engine stop switch 25.ECU (engine control unit) 30.Fuel pump 64.Ignition fuse 8-54...

  • Page 326: Troubleshooting

    FUEL PUMP SYSTEM YamahaR125.COM EAS27570 TROUBLESHOOTING If the fuel pump fails to operate. NOTE: • Before troubleshooting, remove the following part(s): 1. Rider seat 2. Fuel tank NG → 1. Check the fuses. (Main and ignition) Replace the fuse(s). Refer to “CHECKING THE FUS- ES”...
  • Page 327 FUEL PUMP SYSTEM YamahaR125.COM 8-56...

  • Page 328: Electrical Components

    ELECTRICAL COMPONENTS YamahaR125.COM EAS27971 ELECTRICAL COMPONENTS 8-57...
  • Page 329 ELECTRICAL COMPONENTS YamahaR125.COM 1. Main switch 2. Clutch switch 3. Front brake light switch 4. Ignition coil 5. Throttle body sensor assembly (intake air pressure sensor, intake air temperature sensor, throttle position sensor) 6. FID (fast idle solenoid) 7. Rectifier/regulator 8.

  • Page 330: Checking The Switches

    ELECTRICAL COMPONENTS YamahaR125.COM EAS27980 CHECKING THE SWITCHES Br/L (BLACK) Br/L (BLUE) (RED) Sb/W R/W R/W Ch Br/W Br/W PASS 8-59...
  • Page 331 ELECTRICAL COMPONENTS YamahaR125.COM 1. Clutch switch 2. Main switch 3. Front brake light switch 4. Sidestand switch 5. Rear brake light switch 6. Neutral switch 7. Turn signal switch 8. Horn switch 9. Dimmer switch 10. Pass switch 11. Engine stop switch 12.
  • Page 332 ELECTRICAL COMPONENTS YamahaR125.COM Check each switch for continuity with the pocket tester. If the continuity reading is incorrect, check the wiring connections and, if necessary, replace the switch. ECA14370 CAUTION: Never insert the tester probes into the coupler terminal slots “a”. Always insert the probes from the opposite end of the coupler, taking care not to loosen or damage the leads.

  • Page 333: Checking The Bulbs And Bulb Sockets

    ELECTRICAL COMPONENTS YamahaR125.COM 1. Remove: EAS27990 CHECKING THE BULBS AND BULB • Bulb SOCKETS EWA5D71001 WARNING NOTE: Do not check any of the lights that use LEDs. Since the headlight bulbs get extremely hot, keep flammable products and your hands Check each bulb and bulb socket for damage or away from them until they have cooled wear, proper connections, and also for continuity...

  • Page 334: Checking The Fuses

    ELECTRICAL COMPONENTS YamahaR125.COM NOTE: Set the pocket tester selector to “Ω × 1”. Pocket tester 90890-03112 Analog pocket tester YU-03112-C b. If the pocket tester indicates “∞”, replace the fuse. Checking the condition of the bulb sockets L LLL L LLL L LLL L LLL L LLL...

  • Page 335: Checking And Charging The Battery

    ELECTRICAL COMPONENTS YamahaR125.COM 3. Remove: EAS28010 CHECKING AND CHARGING THE BATTERY • Battery EWA13290 4. Check: WARNING • Electrolyte level Batteries generate explosive hydrogen gas The electrolyte level should be between the and contain electrolyte which is made of poi- minimum level mark “a”...
  • Page 336 ELECTRICAL COMPONENTS YamahaR125.COM • When charging a battery, be sure to remove it from the vehicle. (If charging has to be done with the battery mounted on the vehi- cle, disconnect the negative lead from the battery terminal.) • To reduce the chance of sparks, do not plug in the battery charger until the battery charger leads are connected to the battery.

  • Page 337: Checking The Relays

    ELECTRICAL COMPONENTS YamahaR125.COM EAS28040 CHECKING THE RELAYS Result Check each switch for continuity with the pocket Continuity tester. If the continuity reading is incorrect, re- (between “3” and “4”) place the relay. Headlight relay Pocket tester 90890-03112 Analog pocket tester YU-03112-C 1.

  • Page 338: Checking The Diode

    ELECTRICAL COMPONENTS YamahaR125.COM Turn signal relay input voltage DC 12 V M MMM M MMM M MMM M MMM M MMM a. Connect the pocket tester (DC 20 V) to the Br/W turn signal relay terminal as shown. Pocket tester 90890-03112 Analog pocket tester YU-03112-C...

  • Page 339: Checking The Spark Plug Cap

    ELECTRICAL COMPONENTS YamahaR125.COM Primary coil resistance 2.16–2.64 Ω at 20 °C (68 °F) M MMM M MMM M MMM M MMM M MMM a. Disconnect the ignition coil connectors from L/B R/B the ignition coil terminals. Sb/W b. Connect the pocket tester (Ω × 1) to the igni- tion coil as shown.

  • Page 340: Checking The Ignition Spark Gap

    ELECTRICAL COMPONENTS YamahaR125.COM e. Crank the engine by pushing the start switch “ ” and gradually increase the spark gap un- til a misfire occurs. L LLL L LLL L LLL L LLL L LLL EAS28120 CHECKING THE CRANKSHAFT POSITION SENSOR 1.

  • Page 341: Checking The Starter Motor Operation

    ELECTRICAL COMPONENTS YamahaR125.COM • This check is likely to produce sparks, Lean angle sensor output voltage therefore, make sure no flammable gas or Less than 65°: 0.4–1.4 V fluid is in the vicinity. More than 65°: 3.7–4.4 V M MMM M MMM M MMM M MMM...

  • Page 342: Checking The Rectifier/Regulator

    ELECTRICAL COMPONENTS YamahaR125.COM EAS28180 CHECKING THE HORN 1. Check: • Horn resistance Out of specification → Replace. Coil resistance 1.15–1.25 Ω at 20 °C (68 °F) M MMM M MMM M MMM M MMM M MMM a. Disconnect the horn connectors from the horn terminals.

  • Page 343: Checking The Fuel Sender

    ELECTRICAL COMPONENTS YamahaR125.COM EAS28220 EAS28240 CHECKING THE FUEL SENDER CHECKING THE SPEED SENSOR 1. Drain the fuel from the fuel tank. 1. Check: 2. Check: • Speed sensor output voltage Out of specification → Replace. • Fuel sender resistance Out of specification → Replace the fuel send- Output voltage reading cycle 0 V to 5.0 V to 0 V to 5.0 V Sender unit resistance (full)

  • Page 344: Checking The Coolant Temperature Sensor

    ELECTRICAL COMPONENTS YamahaR125.COM c. Measure the radiator fan motor movement. d. Slowly heat the coolant, and then let it cool down to the specified temperature. L LLL L LLL L LLL L LLL L LLL e. Check the coolant temperature sensor resis- EAS28260 CHECKING THE COOLANT TEMPERATURE tance.
  • Page 345 ELECTRICAL COMPONENTS YamahaR125.COM b. Measure the throttle position sensor input Pocket tester voltage. 90890-03112 Out of specification → Replace or repair the Analog pocket tester wire harness. YU-03112-C Throttle position sensor input • Positive tester probe → voltage pink/white “1” •...

  • Page 346: Checking The Fid (Fast Idle Solenoid)

    ELECTRICAL COMPONENTS YamahaR125.COM Gy/R Y Gy/B b. Measure the intake air temperature sensor resistance. L LLL L LLL L LLL L LLL L LLL EAS5D71002 CHECKING THE FID (FAST IDLE SOLENOID) 1. Disconnect: • FID (fast idle solenoid) coupler 2. Check: •...
  • Page 347 YamahaR125.COM TROUBLESHOOTING TROUBLESHOOTING..................9-1 GENERAL INFORMATION ............... 9-1 STARTING FAILURES................9-1 INCORRECT ENGINE IDLING SPEED ............ 9-1 POOR MEDIUM-AND-HIGH-SPEED PERFORMANCE ......9-2 FAULTY GEAR SHIFTING................ 9-2 SHIFT PEDAL DOES NOT MOVE ............9-2 JUMPS OUT OF GEAR................9-2 FAULTY CLUTCH ..................9-2 OVERHEATING ..................

  • Page 348: Troubleshooting

    TROUBLESHOOTING YamahaR125.COM Electrical system EAS28450 TROUBLESHOOTING 1. Battery • Discharged battery EAS28460 • Faulty battery GENERAL INFORMATION 2. Fuse(s) NOTE: • Blown, damaged or incorrect fuse The following guide for troubleshooting does not • Improperly installed fuse cover all the possible causes of trouble. It should 3.

  • Page 349: Poor Medium-And-High-Speed Performance

    TROUBLESHOOTING YamahaR125.COM • Flooded throttle body • Foreign object between transmission gears • Faulty air induction system • Improperly assembled transmission EAS28550 Electrical system JUMPS OUT OF GEAR 1. Battery • Discharged battery Shift shaft • Faulty battery • Incorrect shift pedal position 2.

  • Page 350: Overcooling

    TROUBLESHOOTING YamahaR125.COM 2. Engine oil • Damaged brake hose • Incorrect oil level • Oil or grease on the brake disc • Incorrect oil viscosity • Oil or grease on the brake pad • Inferior oil quality • Incorrect brake fluid level EAS28660 Cooling system FAULTY FRONT FORK LEGS...

  • Page 351: Faulty Lighting Or Signaling System

    TROUBLESHOOTING YamahaR125.COM Tire(s) Turn signal blinks slowly • Uneven tire pressures (front and rear) • Faulty turn signal relay • Incorrect tire pressure • Faulty main switch • Uneven tire wear • Faulty turn signal switch • Incorrect turn signal bulb Wheel(s) •...

  • Page 352: Wiring Diagram

    58. Meter light EAS28740 EAS28750 WIRING DIAGRAM COLOR CODE 59. Coolant temperature warning Black light YZF-R125 2008 Brown 60. High beam indicator light 1. AC magneto Chocolate 61. Turn signal indicator light 2. Crankshaft position sensor Dark green 62. Neutral indicator light 3.
  • Page 353 YamahaR125.COM...
  • Page 354 YamahaR125.COM...
  • Page 355 YamahaR125.COM YZF-R125 YZF-R125 YZF-R125 WIRING DIAGRAM SCHÉMA DE CÂBLAGE SCHALTPLAN SCHEMA ELETTRICO DIAGRAMA ELÉCTRICO B Gy/B Gy/R R Y/G O/B Y/R Y/B G/W G/B Y/W L/Y Gy Br/W G/R Gy/B R Gy/B Br/W P/W Gy/B Gy/R R/B L/B R/B L/B...
  • Page 356 YamahaR125.COM YZF-R125 YZF-R125 YZF-R125 WIRING DIAGRAM SCHALTPLAN DIAGRAMA ELÉCTRICO SCHÉMA DE CÂBLAGE SCHEMA ELETTRICO (BLACK) (BLACK) ( RED ) ( RED ) (BLACK) (BLUE) (BLUE) PASS WIRE HARNESS SUB-WIRE HARNESS (BLACK) (BLACK) WIRE HARNESS SUB-WIRE HARNESS (BLACK) (GREEN) (BLACK) (GREEN)

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