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Yamaha YZ250 Owner's Service Manual
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Yamaha YZ250 Owner's Service Manual

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2018
OWNER'S SERVICE MANUAL
YZ250
YZ250X
Read this manual carefully before operating this vehicle.
YZ250J2
YZ250XJ
LIT-11626-31-12
1SS-28199-16

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Summary of Contents for Yamaha YZ250

  • Page 1 2018 OWNER’S SERVICE MANUAL YZ250 YZ250X Read this manual carefully before operating this vehicle. YZ250J2 YZ250XJ LIT-11626-31-12 1SS-28199-16...
  • Page 2 Read this manual carefully before operating this vehicle. This manual should stay with this vehicle if it is sold.
  • Page 3 YZ250J2/YZ250XJ OWNER'S SERVICE MANUAL ©2017 by Yamaha Motor Corporation, U.S.A. 1st Edition, April 2017 All rights reserved. Any reprinting or unauthorized use without the written permission of Yamaha Motor Corporation U.S.A. is expressly prohibited. Printed in Japan P/N. LIT-11626-31-12 Downloaded from ManualsNet.com...
  • Page 4 INTRODUCTION IMPORTANT MANUAL INFORMATION Congratulations on your purchase of a Yamaha YZ series. This model is the culmination of Particularly important information is distin- Yamaha's vast experience in the production of guished in this manual by the following nota- pacesetting racing machines. It represents the tions.
  • Page 5 SAFETY INFORMATION • PARK THE MACHINE CAREFULLY; TURN OFF THE ENGINE. THIS MACHINE IS DESIGNED STRICTLY Always turn off the engine if you are going to FOR COMPETITION USE, ONLY ON A leave the machine. Do not park the machine CLOSED COURSE.
  • Page 6 YAMAHA MOTOR CORPORATION, U.S.A. YZ MOTORCYCLE LIMITED WARRANTY Downloaded from ManualsNet.com search engine...
  • Page 7 HOW TO USE THIS MANUAL FINDING THE REQUIRED PAGE 1. This manual consists of seven chapters; "General Information", "Specifications", "Regular inspec- tion and adjustments", "Engine", "Chassis", "Electrical" and "Tuning" 2. The table of contents is at the beginning of the manual. Look over the general layout of the book before finding then required chapter and item.
  • Page 8 HOW TO READ DESCRIPTIONS To help identify parts and clarify procedure steps, there are exploded diagrams at the start of each removal and disassembly section. 1. An easy-to-see exploded diagram "1" is provided for removal and disassembly jobs. 2. Numbers "2" are given in the order of the jobs in the exploded diagram. A number that is enclosed by a circle indicates a disassembly step.
  • Page 9 ILLUSTRATED SYMBOLS (Refer Illustrated symbols "1" to "7" are used to identi- fy the specifications appearing in the text. to the illustration) 1. With engine mounted 2. Filling fluid 3. Lubricant 4. Special tool 5. Tightening 6. Specified value, Service limit 7.
  • Page 10 MEMO Downloaded from ManualsNet.com search engine...

  • Page 11: Table Of Contents

    TABLE OF CONTENTS GENERAL INFORMATION SPECIFICATIONS REGULAR INSPECTION AND ADJUSTMENTS ENGINE CHASSIS ELECTRICAL TUNING Downloaded from ManualsNet.com search engine...

  • Page 12: General Information

    CONTENTS CHAPTER 1 GENERAL INFORMATION LOCATION OF IMPORTANT LABELS ..1-1 DESCRIPTION ........... 1-2 CONSUMER INFORMATION ....1-3 INCLUDED PARTS ........1-4 IMPORTANT INFORMATION ....1-5 CHECKING OF CONNECTION ....1-7 SPECIAL TOOLS........1-8 CONTROL FUNCTIONS ......1-11 STARTING AND BREAK-IN ....1-13 TORQUE-CHECK POINTS ......
  • Page 13 CHAPTER 4 ENGINE SEAT, FUEL TANK AND SIDE COVERS . 4-1 EXHAUST PIPE AND SILENCER ..... 4-4 RADIATOR..........4-6 CARBURETOR AND REED VALVE ..4-9 CYLINDER HEAD, CYLINDER AND PISTON ............ 4-18 CLUTCH ........... 4-32 KICK SHAFT AND SHIFT SHAFT... 4-38 YPVS GOVERNOR ........
  • Page 14 CHAPTER 7 TUNING ENGINE ............7-1 CHASSIS............ 7-9 Downloaded from ManualsNet.com search engine...
  • Page 15 LOCATION OF IMPORTANT LABELS GENERAL INFORMATION LOCATION OF IMPORTANT LABELS Please read the following important labels carefully before operating this vehicle. Downloaded from ManualsNet.com search engine...
  • Page 16 DESCRIPTION DESCRIPTION 1. Clutch lever 14. Fuel cock 2. Engine stop switch 15. Starter knob 3. Front brake lever 16. Drive chain 4. Throttle grip 17. Air filter 5. Radiator cap 18. Shift pedal 6. Fuel tank cap 19. Front fork 7.
  • Page 17 There are two significant reasons for knowing the serial number of your machine: 1. When ordering parts, you can give the num- ber to your Yamaha dealer for positive iden- tification of the model you own. 2. If your machine is stolen, the authorities will need the number to search for and identify your machine.
  • Page 18 INCLUDED PARTS INCLUDED PARTS SET PIN This set pin "1" is used to remove and install the DETACHABLE SIDESTAND (YZ250) push rod of the engine. This sidestand "1" is used to support only the machine when standing or transporting it.
  • Page 19 5. Keep away from fire. 2. Use proper tools and cleaning equipment. ALL REPLACEMENT PARTS Refer to "SPECIAL TOOLS" section. 1. We recommend to use Yamaha genuine parts for all replacements. Use oil and/or grease recommended by Yamaha for as- sembly and adjustment.
  • Page 20 IMPORTANT INFORMATION LOCK WASHERS/PLATES AND COTTER CIRCLIPS PINS 1. All circlips should be inspected carefully be- 1. All lock washers/plates "1" and cotter pins fore reassembly. Always replace piston pin must be replaced when they are removed. clips after one use. Replace distorted cir- Lock tab(s) should be bent along the bolt or clips.
  • Page 21 CHECKING OF CONNECTION CHECKING OF CONNECTION Dealing with stains, rust, moisture, etc. on the connector. 1. Disconnect: • Connector 2. Dry each terminal with an air blower. 3. Connect and disconnect the connector two or three times. 4. Pull the lead to check that it will not come off. 5.
  • Page 22 SPECIAL TOOLS SPECIAL TOOLS The proper special tools are necessary for complete and accurate tune-up and assembly. Using the correct special tool will help prevent damage caused by the use of improper tools or improvised tech- niques. The shape and part number used for the special tool differ by country, so two types are pro- vided.
  • Page 23 SPECIAL TOOLS Tool name/Part number How to use Illustration Radiator cap tester These tools are used for YU-24460-A, 90890-01325 checking the cooling system. Radiator cap tester adapter YU-33984, 90890-01352 Steering nut wrench This tool is used when tighten YU-A9472, 90890-01403 the steering ring nut to speci- fication.
  • Page 24 Ignition checker tem components. 90890-06754 Digital tachometer This tool is needed for ob- YU-39951-B, 90890-06760 serving engine rpm. Yamaha bond No. 1215 This sealant (Bond) is used 90890-85505 for crankcase mating surface, (Three bond No. 1215®) etc. 1-10 Downloaded from ManualsNet.com...
  • Page 25 CONTROL FUNCTIONS CONTROL FUNCTIONS KICKSTARTER LEVER Rotate the kickstarter lever "1" away from the ENGINE STOP SWITCH engine. Push the starter down lightly with your The engine stop switch "1" is located on the left foot until the gears engage, then kick smoothly handlebar.
  • Page 26 FUEL COCK YZ250 The fuel cock supplies fuel from the tank to car- buretor and also filters the fuel. The fuel cock STARTER KNOB (CHOKE)
  • Page 27 ELEMENT" section in the CHAPTER 3, apply Never mix two types of oil in the same the Yamaha foam air filter oil or other quality batch; clotting of the oil could result. If you foam air filter oil to the element. (Excess oil in...
  • Page 28 STARTING AND BREAK-IN BREAK-IN PROCEDURES 1. Before starting the engine, fill the fuel tank • After the break-in or before each race, you with a break-in oil-fuel mixture as follows. must check the entire machine for loose Mixing oil: fittings and fasteners as per "TORQUE- YAMALUBE "2-R"...
  • Page 29 TORQUE-CHECK POINTS TORQUE-CHECK POINTS Frame construction Frame to rear frame Combined seat and fuel tank Fuel tank to frame Exhaust system Silencer to rear frame Engine mounting Frame to engine Engine bracket to engine Engine bracket to frame Steering Steering stem to handlebar Steering stem to frame Steering stem to upper bracket Upper bracket to handlebar...
  • Page 30 MAINTENANCE AFTER BREAK-IN MAINTENANCE AFTER BREAK-IN • Cable Grease and adjust cables. After a break-in, perform careful maintenance • Drive chain to get ready for the next practice or race. Lubricate the drive chain and adjust its ten- Refer to "PRE-OPERATION INSPECTION sion.
  • Page 31 CLEANING AND STORAGE CLEANING AND STORAGE STORAGE If your machine is to be stored for 60 days or CLEANING more, some preventive measures must be tak- Frequent cleaning of your machine will en- en to avoid deterioration. After cleaning the ma- hance its appearance, maintain good overall chine thoroughly, prepare it for storage as performance, and extend the life of many com-...

  • Page 32: Specifications

    GENERAL SPECIFICATIONS SPECIFICATIONS GENERAL SPECIFICATIONS Model name: YZ250J2 (USA, CAN) YZ250J (AUS, NZ, ZA) YZ250 (EUROPE) YZ250XJ (USA, CAN, AUS) Model code number: YZ250 1SSS (USA, CAN) 1SST (EUROPE) 1SSV (AUS, NZ, ZA) YZ250X BF1A (USA, CAN) BF1C (AUS) Dimensions:...
  • Page 33 GENERAL SPECIFICATIONS Compression ratio YZ250 8.9–10.6 : 1 YZ250X 7.9–9.4 : 1 Starting system Kickstarter Lubrication system: Premix (30 : 1)(YAMALUBE 2-R) Oil type or grade (2-stroke): Transmission oil Recommended brand: YAMALUBE SAE10W-40 API service SG type or higher JASO standard MA Periodic oil change 0.75 L (0.66 Imp qt, 0.79 US qt)
  • Page 34 Frame type Semi double cradle Caster angle 27.7 ° Trail 122 mm (4.8 in) Tire: Type With tube Size (front) YZ250 80/100-21 51M YZ250X 90/90-21 54M Size (rear) YZ250 110/90-19 62M YZ250X 110/100-18 64M Tire pressure (front and rear) 100 kPa (1.00 kgf/cm...
  • Page 35 MAINTENANCE SPECIFICATIONS MAINTENANCE SPECIFICATIONS ENGINE Item Standard Limit Cylinder head: Combustion chamber volume YZ250 21.35–21.65 cm (1.30–1.32 cu.in) ---- YZ250X 23.45–23.75 cm (1.43–1.45 cu.in) ---- Warp limit ---- 0.03 mm (0.0012 in) Cylinder: Bore size 66.400–66.414 mm (2.6142–2.6147 in) 66.500 mm (2.6181 in)
  • Page 36 Cam drum and guide bar ---- Guide bar bending limit ---- 0.050 mm (0.0020 in) Kickstarter type: Ratchet ---- Air filter oil grade (oiled filter): Yamaha foam air filter oil or other quality ---- foam air filter oil Downloaded from ManualsNet.com search engine...
  • Page 37 MAINTENANCE SPECIFICATIONS Item Standard Limit Carburetor: USA, CAN EUROPE AUS, NZ, ZA ← ← Type/Manufacturer PWK38S/ ---- KEIHIN ← I.D. mark 1P87 50 1P86 40 ---- ← Main jet (M.J.) #178 #180 ---- ← ← Main air jet (M.A. J.) #200 ---- ←...
  • Page 38 Optional spring ---- ← Oil capacity 515.0 cm (18.16 ---- Imp oz, 17.41 US ← Oil grade Yamaha Suspen- ---- sion Oil S1 ← Inner tube outer diameter 48 mm (1.9 in) ---- Front fork top end ← YZ250 0 mm (0 in)
  • Page 39 Front wheel type Spoke wheel ---- Rear wheel type Spoke wheel ---- Front rim size/material 21 × 1.60/Aluminum ---- Rear rim size/material YZ250 19 × 2.15/Aluminum ---- YZ250X 18 × 2.15/Aluminum ---- Rim runout limit: Radial ---- 2.0 mm (0.08 in)
  • Page 40 (Black-Black/Red) 44.0–66.0 Ωat 20 °C (68 °F) Charging coil 2 resistance (color) ---- (Green/Blue-Green/White) 248.0–372.0 Ωat 20 °C (68 °F) Pickup coil resistance (color) ---- (White/Blue-White/Red) CDI unit-model/manufacturer YZ250 1P8-00/YAMAHA ---- YZ250X BF1-00/YAMAHA ---- Ignition coil: Model/manufacturer 1P8-00/YAMAHA ---- Minimum spark gap 6.0 mm (0.24 in)
  • Page 41 TIGHTENING TORQUES TIGHTENING TORQUES ENGINE △ - marked portion shall be checked for torque tightening after break-in or before each race. Threa Item Q'ty Tightening torque Remarks d size Spark plug M14S 20 Nm (2.0 m•kg, 14 ft•lb) Copper Cylinder head (nut) 25 Nm (2.5 m•kg, 18 ft•lb) washer Cylinder head (stud)
  • Page 42 TIGHTENING TORQUES Threa Item Q'ty Tightening torque Remarks d size △ Exhaust pipe stay (front) 25 Nm (2.5 m•kg, 18 ft•lb) △ Exhaust pipe stay (rear) 12 Nm (1.2 m•kg, 8.7 ft•lb) Silencer: △ Silencer and frame 12 Nm (1.2 m•kg, 8.7 ft•lb) Fiber 10 Nm (1.0 m•kg, 7.2 ft•lb) Crankcase...
  • Page 43 TIGHTENING TORQUES CHASSIS △ - marked portion shall be checked for torque tightening after break-in or before each race. Threa Item Q'ty Tightening torque Remarks d size △ Upper bracket and outer tube 21 Nm (2.1 m•kg, 15 ft•lb) △ Lower bracket and outer tube 21 Nm (2.1 m•kg, 15 ft•lb) △...
  • Page 44 TIGHTENING TORQUES Threa Item Q'ty Tightening torque Remarks d size △ Brake caliper (front and rear) and 18 Nm (1.8 m•kg, 13 ft•lb) pad pin △ Brake caliper (front and rear) and 6 Nm (0.6 m•kg, 4.3 ft•lb) bleed screw △...
  • Page 45 TIGHTENING TORQUES Threa Item Q'ty Tightening torque Remarks d size △ Swingarm and brake hose holder 3 Nm (0.3 m•kg, 2.2 ft•lb) Swingarm and patch 2 Nm (0.2 m•kg, 1.4 ft•lb) Drive chain tensioner 16 Nm (1.6 m•kg, 11 ft•lb) Drive chain support and swingarm 7 Nm (0.7 m•kg, 5.1 ft•lb) Seal guard and swingarm...
  • Page 46 TIGHTENING TORQUES GENERAL TORQUE SPECIFICATIONS This chart specifies torque for standard fasten- ers with standard I.S.O. pitch threads. Torque specifications for special components or as- semblies are included in the applicable sec- tions of this book. To avoid warpage, tighten multi-fastener assemblies in a crisscross fash- ion, in progressive stages, until full torque is reached.
  • Page 47 TIGHTENING TORQUES DEFINITION OF UNITS Unit Read Definition Measure millimeter meter Length centimeter meter Length kilogram gram Weight Newton 1 kg × m/sec Force Newton meter N × m Torque m•kg Meter kilogram m × kg Torque Pascal Pressure N/mm Newton per millimeter N/mm Spring rate...
  • Page 48 CABLE ROUTING DIAGRAM CABLE ROUTING DIAGRAM 2-17 Downloaded from ManualsNet.com search engine...
  • Page 49 CABLE ROUTING DIAGRAM 1. Engine stop switch lead 2. Throttle cable 3. Clutch cable 4. Clamp 5. Wire harness 6. Radiator breather hose 7. Air vent hose 8. Crankcase breather hose 9. Overflow hose A. Pass the clutch cable on the outside of the throttle cable and engine stop switch lead.
  • Page 50 CABLE ROUTING DIAGRAM 2-19 Downloaded from ManualsNet.com search engine...
  • Page 51 CABLE ROUTING DIAGRAM 1. Ignition coil lead 2. Clamp 3. CDI magneto lead 4. Neutral switch lead 5. Radiator breather hose 6. YPVS breather hose 7. Connector cover A. Clamp the ignition coil lead to the frame at its locating tape. Clamp it in front of the ra- diator fitting boss.
  • Page 52 CABLE ROUTING DIAGRAM 2-21 Downloaded from ManualsNet.com search engine...
  • Page 53 CABLE ROUTING DIAGRAM 1. Clamp 2. Wire harness 3. High tension cord 4. CDI unit band 5. CDI unit 6. CDI unit lead 7. Joint connector 8. Connector cover 9. Radiator hose 10. Radiator breather hose 11. CDI unit stay A.
  • Page 54 CABLE ROUTING DIAGRAM 2-23 Downloaded from ManualsNet.com search engine...
  • Page 55 CABLE ROUTING DIAGRAM 1. Master cylinder 2. Brake hose holder 3. Brake hose A. Install the brake hose so that its pipe por- tion directs as shown and lightly touches the projection on the caliper. B. Pass the brake hose into the brake hose holders.
  • Page 56 CABLE ROUTING DIAGRAM 2-25 Downloaded from ManualsNet.com search engine...
  • Page 57 CABLE ROUTING DIAGRAM 1. Brake hose 2. Master cylinder 3. Engine stop switch lead 4. Engine stop switch 5. Throttle cable 6. Clutch cable 7. Clamp 8. Cable guide A. Install the brake hose so that its pipe por- tion directs as shown and lightly touches the projection on the master cylinder.

  • Page 58: Regular Inspection And Adjustments

    If you are a doubt as to what intervals to follow in maintaining and lubricating your machine, consult your Yamaha dealer. • Periodic inspection is essential in making full use of the machine performance. The service life of the parts varies substantially according to the environment in which the machine runs (e.g., rain,...
  • Page 59 MAINTENANCE INTERVALS Every Every Every After race third fifth As re- Item break Remarks (about (about (about quired 12.5 hours) hours) hours) TRANSMISSION ● ● Replace oil Recommended brand: YAMALUBE SAE10W-40 API service SG type or higher JASO standard MA ●...
  • Page 60 Retighten Refer to "STARTING AND BREAK-IN" section in the CHAPTER 1. AIR FILTER ● ● Clean and lubricate Use the Yamaha foam air filter oil or other quality foam air filter oil. ● Replace FRAME ● ● Clean and inspect FUEL TANK, COCK ●...
  • Page 61 Retighten sprocket bolt ● Inspect bearings ● Replace bearings ● Lubricate Lithium base grease THROTTLE, CONTROL CABLE ● ● Check routing and con- nection ● ● Lubricate Yamaha cable lube or SAE 10W-40 motor oil Downloaded from ManualsNet.com search engine...
  • Page 62 PRE-OPERATION INSPECTION AND MAINTENANCE PRE-OPERATION INSPECTION AND MAINTENANCE Before riding for break-in operation, practice or a race, make sure the machine is in good operating condition. Before using this machine, check the following points. GENERAL INSPECTION AND MAINTENANCE Item Routine Page Check that coolant is filled up to the radiator cap.

  • Page 63: Engine

    ENGINE ENGINE CHANGING THE COOLANT CHECKING THE COOLANT LEVEL Do not remove the radiator cap when the en- gine is hot. Do not remove the radiator cap "1", drain bolt and hoses when the engine and radia- tor are hot. Scalding hot fluid and steam Take care so that coolant does not splash may be blown out under pressure, which on painted surfaces.
  • Page 64 ENGINE CHECKING THE RADIATOR CAP 1. Inspect: • Do not mix more than one type of ethylene • Seal (radiator cap) "1" glycol antifreeze containing corrosion in- • Valve and valve seat "2" hibitors for aluminum engine. Crack/damage → Replace. •...
  • Page 65 ENGINE CHECKING THE COOLING SYSTEM ADJUSTING THE CLUTCH LEVER 1. Inspect: POSITION • Coolant level 1. Adjust: 2. Attach: • Clutch lever position • Radiator cap tester "1" and adapter "2" Clutch lever position adjustment steps: Radiator cap tester: a. Loosen the locknuts "1". YU-24460-A/90890-01325 b.
  • Page 66 ENGINE 2. Adjust: ADJUSTING THE THROTTLE GRIP FREE • Clutch lever free play PLAY 1. Check: • Throttle grip free play "a" Handlebar side Out of specification → Adjust. a. Turn the adjuster "1" until the specified clutch lever free play is obtained. Throttle grip free play "a": 3.0–5.0 mm (0.12–0.20 in) If the clutch lever free play cannot be obtained...
  • Page 67 Damage → Replace. Throttle cable cap: 4. Apply: 0.5 Nm (0.05 m•kg, 0.36 ft•lb) • Yamaha foam air filter oil or other quality foam air filter oil • Cap cover CLEANING THE AIR FILTER ELEMENT Squeeze out the excess oil. Element should be wet but not dripping.
  • Page 68 ENGINE 5. Install: CHECKING THE TRANSMISSION OIL • Air filter guide "1" LEVEL 1. Start the engine, warm it up for several min- utes and wait for five minutes. Align the projection "a" on filter guide with the 2. Place the machine on a level place and hold hole "b"...
  • Page 69 ENGINE CHANGING THE TRANSMISSION OIL 7. Check: 1. Start the engine and warm it up for several • Oil leakage minutes and wait for five minute. 8. Check: 2. Place the machine on a level place and hold • Transmission oil level it on upright position by placing the suitable 9.
  • Page 70 ENGINE ADJUSTING THE ENGINE IDLING SPEED 1. Start the engine and thoroughly warm it up. 2. Adjust: • Engine idling speed Adjustment steps: a. Turn the throttle stop screw "1" until the en- gine runs at the lowest possible speed. To increase idle speed →...

  • Page 71: Chassis

    CHASSIS CHASSIS d. Place the other end of the tube into a con- tainer. BLEEDING THE HYDRAULIC BRAKE e. Slowly apply the brake lever or pedal sever- SYSTEM al times. f. Pull the lever in or push down on the pedal. Hold the lever or pedal in position.
  • Page 72 CHASSIS 2. Remove: 2. Adjust: • Brake lever cover • Brake pedal height 3. Adjust: • Brake lever position Pedal height adjustment steps: a. Loosen the locknut "1". Brake lever position adjustment steps: b. Turn the adjusting nut "2" until the pedal a.
  • Page 73 CHASSIS 2. Replace: f. Loosen the bleed screw and push the brake • Brake pad caliper pistons in. Brake pad replacement steps: Do not reuse the drained brake fluid. a. Remove the pad pin plug "1". g. Tighten the bleed screw. Bleed screw: 6 Nm (0.6 m•kg, 4.3 ft•lb) h.
  • Page 74 CHASSIS j. Install the pad pin plug "10". 2. Replace: • Brake pad Pad pin plug: 3 Nm (0.3 m•kg, 2.2 ft•lb) Brake pad replacement steps: a. Remove the protector "1" and pad pin plug "2". 3. Inspect: • Brake fluid level b.
  • Page 75 CHASSIS k. Install the pad pin plug "15" and protector "16". Pad pin plug: 3 Nm (0.3 m•kg, 2.2 ft•lb) Bolt (protector): 7 Nm (0.7 m•kg, 5.1 ft•lb) f. Loosen the bleed screw and push the brake caliper piston in. Do not reuse the drained brake fluid.
  • Page 76 CHASSIS CHECKING THE BRAKE FLUID LEVEL CHECKING THE DRIVE CHAIN 1. Place the brake master cylinder so that its YZ250 top is in a horizontal position. 1. Measure: 2. Inspect: • Drive chain length (15 links) "a" Out of specification → Replace.
  • Page 77 CHASSIS 6. Lubricate: • Drive chain Drive chain lubricant: SAE 10W-40 motor oil or suitable chain lubricants 4. Check: • Drive chain stiffness "a" Clean and oil the drive chain and hold as il- lustrated. Stiff → Replace the drive chain. YZ250X 1.
  • Page 78 CHASSIS 3. Clean: 6. Install: • Drive chain • Chain joint "1" Brush off as much dirt as possible. Then • O-ring "2" clean the drive chain using the chain clean- • Drive chain "3" • Link plate "4" When installing the drive chain, apply the lithi- This machine has a drive chain with small um soap base grease on the chain joint and O- rubber O-rings "1"...
  • Page 79 CHASSIS 8. Lubricate: 3. Adjust: • Drive chain • Drive chain slack Drive chain lubricant: Drive chain slack adjustment steps: SAE 10W-40 motor oil or suitable a. Loosen the axle nut "1" and locknuts "2". chain lubricants b. Adjust the drive chain slack by turning the adjusters "3".
  • Page 80 CHASSIS 2. Clean: • Dust seal "a" • Oil seal "b" • Clean the dust seal and oil seal after every run. • Apply the lithium soap base grease on the in- ner tube. CHECKING THE FRONT FORK PROTECTOR GUIDE 1.
  • Page 81 This is the position which is back by the spe- cific number of clicks from the fully turned-in cific number of clicks from the fully turned-in position. position. Standard position: Standard position: YZ250: YZ250: 12 clicks out 12 clicks out YZ250X: YZ250X: 10 clicks out...
  • Page 82 CHASSIS 4. Adjust: • Spring preload Adjustment steps: a. Loosen the locknut "1". b. Loosen the adjuster "2" until there is some clearance between the spring and adjuster. c. Measure the spring free length "a". d. Turn the adjuster "2". Stiffer →Increase the spring preload.
  • Page 83 This is the position which is back by the spe- bracket.) cific number of clicks from the fully turned-in Standard position: position. (Which align the punch mark "a" on YZ250: the adjuster with the punch mark "b" on the 9–12 clicks out high compression damping adjuster.) YZ250X: Standard position: 10–13 clicks out...
  • Page 84 (Which align the punch mark "a" on the adjuster with the punch mark "b" on the adjuster body.) Standard position: YZ250: 1-3/8±1/6 turns out YZ250X: 1-5/8±1/6 turns out 3-27 Downloaded from ManualsNet.com...
  • Page 85 CHASSIS CHECKING AND TIGHTENING THE CHECKING THE WHEELS SPOKES 1. Inspect: The following procedure applies to all of the • Wheel runout spokes. Elevate the wheel and turn it. Abnormal runout → Replace. 1. Check: • Spoke Bend/damage → Replace. Loose spoke →...
  • Page 86 CHASSIS 3. Check: • Steering smooth action Turn the handlebar lock to lock. Unsmooth action → Adjust steering ring nut. e. Loosen the steering ring nut one turn. f. Retighten the steering ring nut using the steering nut wrench. 4. Adjust: Avoid over-tightening.
  • Page 87 CHASSIS 3-30 Downloaded from ManualsNet.com search engine...
  • Page 88 CHASSIS LUBRICATION 3-31 Downloaded from ManualsNet.com search engine...
  • Page 89 9. Tube guide cable winding portion 10. Throttle cable end 11. Clutch cable end 12. Sidestand sliding surface A. Use Yamaha cable lube or equivalent on these areas. B. Use SAE 10W-40 motor oil or suitable chain lubricants. C. Lubricate the following areas with high quality, lightweight lithium-soap base grease.

  • Page 90: Electrical

    ELECTRICAL ELECTRICAL CHECKING THE SPARK PLUG 1. Remove: • Spark plug 2. Inspect: • Electrode "1" Wear/damage → Replace. • Insulator color "2" Normal condition is a medium to light tan color. CHECKING THE IGNITION TIMING Distinctly different color → Check the engine 1.
  • Page 91 ELECTRICAL 4. Set the dial gauge to zero at TDC. 5. From TDC, rotate the rotor clockwise until the dial gauge indicates that the piston is at a specified distance from TDC. Ignition timing (B.T.D.C.): 0.18 mm (0.01 in) 6. Check: •...
  • Page 92 This section is intended for those who have basic knowledge and skill concerning the servicing of Yamaha motorcycles (e.g., Yamaha dealers, service engineers, etc.) Those who have little knowl- edge and skill concerning servicing are requested not to undertake inspection, adjustment, disas- sembly, or reassembly only by reference to this manual.
  • Page 93 SEAT, FUEL TANK AND SIDE COVERS 19 Nm (1.9 m kg, 13 ft lb) 7 Nm (0.7 m kg, 5.1 ft lb) 6 Nm (0.6 m kg, 4.3 ft lb) 7 Nm (0.7 m kg, 5.1 ft lb) 7 Nm (0.7 m kg, 5.1 ft lb) 7 Nm (0.7 m kg, 5.1 ft lb) 10 Nm (1.0 m kg, 7.2 ft lb) 19 Nm (1.9 m kg, 13 ft lb)
  • Page 94 SEAT, FUEL TANK AND SIDE COVERS REMOVING THE SIDE COVER 1. Remove: • Bolt (side cover) • Side cover (left and right) "1" Draw the side cover backward to remove it be- cause its claws "a" are inserted in the air filter case.
  • Page 95 EXHAUST PIPE AND SILENCER EXHAUST PIPE AND SILENCER REMOVING THE EXHAUST PIPE AND SILENCER 12 Nm (1.2 m kg, 8.7 ft lb) 12 Nm (1.2 m kg, 8.7 ft lb) 10 Nm (1.0 m kg, 7.2 ft lb) 12 Nm (1.2 m kg, 8.7 ft lb) 25 Nm (2.5 m kg, 18 ft lb) 14 Nm (1.4 m kg, 10 ft lb) Order...
  • Page 96 4. Install: • Inner pipe ® Fully apply Quick gasket (Yamaha bond No.1215) or equivalent as shown. Yamaha bond No. 1215: 90890-85505 (Three bond No. 1215®) 5. Install: • Bolt (fiber) "1" Bolt (fiber): 10 Nm (1.0 m•kg, 7.2 ft•lb) •...
  • Page 97 RADIATOR RADIATOR REMOVING THE RADIATOR 2 Nm (0.2 m kg, 1.4 ft lb) 10 Nm (1.0 m kg, 7.2 ft lb) 10 Nm (1.0 m kg, 7.2 ft lb) 10 Nm (1.0 m kg, 7.2 ft lb) 10 Nm (1.0 m kg, 7.2 ft lb) 2 Nm (0.2 m kg, 1.4 ft lb) Order Part name...
  • Page 98 RADIATOR HANDLING NOTE 2. Install: • Right radiator "1" • Washer "2" Do not remove the radiator cap when the en- • Bolt (right radiator) "3" gine and radiator are hot. Scalding hot fluid Bolt (right radiator): and steam may be blown out under pres- 10 Nm (1.0 m•kg, 7.2 ft•lb) sure, which could cause serious injury.
  • Page 99 RADIATOR 5. Install: • Radiator guard "1" • Bolt (radiator guard) "2" Bolt (radiator guard): 10 Nm (1.0 m•kg, 7.2 ft•lb) Fit the hook "a" on the inner side first into the ra- diator. Downloaded from ManualsNet.com search engine...
  • Page 100 CARBURETOR AND REED VALVE CARBURETOR AND REED VALVE REMOVING THE CARBURETOR AND REED VALVE 10 Nm (1.0 m kg, 7.2 ft lb) 1 Nm (0.1 m kg, 0.7 ft lb) Order Part name Q'ty Remarks Refer to "SEAT, FUEL TANK AND Fuel tank SIDE COVERS"...
  • Page 101 CARBURETOR AND REED VALVE DISASSEMBLING THE CARBURETOR 4 Nm (0.4 m kg, 2.9 ft lb) Order Part name Q'ty Remarks Mixing chamber top Throttle valve Refer to removal section. Needle holder Jet needle Float chamber Float pin Float Needle valve Main jet Pilot jet Starter plunger...
  • Page 102 CARBURETOR AND REED VALVE HANDLING NOTE Do not loosen the screw (throttle position sensor) "1" except when changing the throttle position sensor due to failure be- cause it will cause a drop in engine perfor- mance. CHECKING THE CARBURETOR 1. Inspect: •...
  • Page 103 CARBURETOR AND REED VALVE CHECKING THE NEEDLE VALVE 1. Inspect: • Needle valve "1" • Valve seat "2" Grooved wear "a" → Replace. Dust "b" → Clean. MEASURING AND ADJUSTING THE FLOAT HEIGHT 1. Measure: • Float height "a" Out of specification → Adjust. Float height: CHECKING THE THROTTLE VALVE 6.5 mm (0.26 in)
  • Page 104 CARBURETOR AND REED VALVE INSTALLING THE REED VALVE 1. Install: CHECKING THE FLOAT • Reed valve "1" 1. Inspect: • Stopper (reed valve) "2" • Float "1" • Screw (reed valve) "3" Damage → Replace. Screw (reed valve): 1 Nm (0.1 m•kg, 0.7 ft•lb) •...
  • Page 105 CARBURETOR AND REED VALVE 3. Install: 3. Install: • Carburetor joint "1" • Pilot air screw "1" • Bolt (carburetor joint) "2" • Throttle stop screw "2" Bolt (carburetor joint): Note the following installation points: 10 Nm (1.0 m•kg, 7.2 ft•lb) a.
  • Page 106 CARBURETOR AND REED VALVE 5. Install: • Pilot jet "1" Install the air vent hoses and overflow hose to • Main jet "2" the carburetor with their ends not having the cuts "a" toward the carburetor. 6. Install: • Needle valve "1" 9.
  • Page 107 CARBURETOR AND REED VALVE INSTALLING THE CARBURETOR 1. Install: • Carburetor "1" Install the projection between the carburetor joint slots. 2. Tighten: • Screw (carburetor joint) "1" 11.Install: • Mixing chamber top "1" • Screw (mixing chamber top) "2" To carburetor "3". •...
  • Page 108 CARBURETOR AND REED VALVE 4. Connect: • Throttle position sensor lead "1" • Solenoid valve lead "2" Refer to "CABLE ROUTING DIAGRAM" section in the CHAPTER 2. 5. Adjust: • Idle speed Refer to "ADJUSTING THE ENGINE IDLING SPEED" section in the CHAPTER 3. 4-17 Downloaded from ManualsNet.com...
  • Page 109 CYLINDER HEAD, CYLINDER AND PISTON CYLINDER HEAD, CYLINDER AND PISTON REMOVING THE CYLINDER HEAD AND CYLINDER 34 Nm (3.4 m kg, 24 ft lb) 64 Nm (6.4 m kg, 46 ft lb) 20 Nm (2.0 m kg, 14 ft lb) 5 Nm (0.5 m kg, 3.6 ft lb) 25 Nm (2.5 m kg, 18 ft lb) 13 Nm (1.3 m kg, 9.4 ft lb)
  • Page 110 CYLINDER HEAD, CYLINDER AND PISTON 34 Nm (3.4 m kg, 24 ft lb) 64 Nm (6.4 m kg, 46 ft lb) 20 Nm (2.0 m kg, 14 ft lb) 5 Nm (0.5 m kg, 3.6 ft lb) 25 Nm (2.5 m kg, 18 ft lb) 13 Nm (1.3 m kg, 9.4 ft lb) 42 Nm (4.2 m kg, 30 ft lb) 5 Nm (0.5 m kg, 3.6 ft lb)
  • Page 111 CYLINDER HEAD, CYLINDER AND PISTON REMOVING THE PISTON AND POWER VALVE 6 Nm (0.6 m kg, 4.3 ft lb) 4 Nm (0.4 m kg, 2.9 ft lb) 4 Nm (0.4 m kg, 2.9 ft lb) 4 Nm (0.4 m kg, 2.9 ft lb) 4 Nm (0.4 m kg, 2.9 ft lb) Order Part name...
  • Page 112 CYLINDER HEAD, CYLINDER AND PISTON 6 Nm (0.6 m kg, 4.3 ft lb) 4 Nm (0.4 m kg, 2.9 ft lb) 4 Nm (0.4 m kg, 2.9 ft lb) 4 Nm (0.4 m kg, 2.9 ft lb) 4 Nm (0.4 m kg, 2.9 ft lb) Order Part name Q'ty...
  • Page 113 CYLINDER HEAD, CYLINDER AND PISTON REMOVING THE PUSH ROD Piston pin puller set: 1. Remove: YU-01304/90890-01304 • Bolt (push rod) "1" • Push rod "2" Do not use a hammer to drive the piston pin Insert the set pin "3" included in owner's tool kit out.
  • Page 114 CYLINDER HEAD, CYLINDER AND PISTON 2. Inspect: • Cylinder head water jacket Crust of minerals/Rust → Replace. 3. Measure: • Cylinder head warpage Out of specification → Resurface. Cylinder head warpage: Less than 0.03 mm (0.0012 in) Warpage measurement and resurfacing 2.
  • Page 115 CYLINDER HEAD, CYLINDER AND PISTON CHECKING THE PISTON PIN AND SMALL END BEARING 1. Inspect: • Piston pin • Small end bearing Signs of heat discoloration → Replace. CHECKING THE PISTON 1. Eliminate: • Carbon deposits From the piston crown "a" and ring groove "b".
  • Page 116 CYLINDER HEAD, CYLINDER AND PISTON 3. Check: • Free play (when the piston pin "1" is in place in the piston "2") There should be no noticeable for the play. Free play exists→Replace piston pin and/or piston. 3. Measure: • Side clearance Use a thickness gauge "1".
  • Page 117 CYLINDER HEAD, CYLINDER AND PISTON Piston clearance: Standard <Limit> 0.045–0.050 mm 0.100 mm (0.0039 in) (0.0018–0.0020 in) CHECKING THE COMBINATION OF PISTON AND CYLINDER 1. Check: • Cylinder mark "a" 3. Combination: Cylinder mark "a" Cylinder size Combine the piston and cylinder by the fol- 66.400–66.402 mm lowing chart.
  • Page 118 CYLINDER HEAD, CYLINDER AND PISTON CHECKING THE POWER VALVE HOLE ON CYLINDER Install the link rod with the cuts "a" in its arm 1. Remove: ends fitting over the pins "b" on the power • Carbon deposits valves 2. From power valve hole surface "a". Do not use a sharp instrument.
  • Page 119 CYLINDER HEAD, CYLINDER AND PISTON • Install the valve shaft with its cut "b" aligning 6. Check: with the thrust plate "7", and then rotate the • Power valve 1 smooth movement Unsmooth movement → Repair or replace. valve shaft so that its cut faces upward. 7.
  • Page 120 CYLINDER HEAD, CYLINDER AND PISTON INSTALLING THE PISTON RING AND 3. Install: PISTON • Piston "1" 1. Install: • Piston pin "2" • Piston ring "1" • Piston pin clip "3" • Take care not to scratch the piston or damage •...
  • Page 121 CYLINDER HEAD, CYLINDER AND PISTON INSTALLING THE CYLINDER HEAD AND CYLINDER 1. Apply: • Engine oil To piston "1", piston ring "2" and cylinder surface. 4. Install: • Push rod "1" • Bolt (push rod) "2" Bolt (push rod): 5 Nm (0.5 m•kg, 3.6 ft•lb) 2.
  • Page 122 CYLINDER HEAD, CYLINDER AND PISTON 6. Install: • O-ring "1" • Dowel pin "2" Apply the lithium soap base grease on the O- rings. 9. Install: • Spark plug "1" Spark plug: 20 Nm (2.0 m•kg, 14 ft•lb) • Spark plug cap "2" 7.
  • Page 123 CLUTCH CLUTCH REMOVING THE CLUTCH 10 Nm (1.0 m kg, 7.2 ft lb) 10 Nm (1.0 m kg, 7.2 ft lb) Order Part name Q'ty Remarks Refer to "CHANGING THE TRANS- Drain the transmission oil. MISSION OIL" section in the CHAP- TER 3.
  • Page 124 CLUTCH REMOVING THE CLUTCH BOSS 75 Nm (7.5 m kg, 54 ft lb) 6 Nm (0.6 m kg, 4.3 ft lb) Order Part name Q'ty Remarks Push rod 1 Circlip Washer Bearing Push rod 2 Nut (clutch boss) Refer to removal section. Lock washer Refer to removal section.
  • Page 125 1. Measure: • Clutch spring free length "a" Out of specification → Replace springs as a set. Clutch spring free length "a": YZ250: 50.00 mm (1.97 in) <Limit>: 48.00 mm (1.89 in) YZ250X: 44.00 mm (1.73 in) <Limit>: 41.80 mm (1.65 in) A.
  • Page 126 CLUTCH CHECKING THE CLUTCH PLATES INSTALLING THE PUSH LEVER SHAFT 1. Measure: 1. Install: • Clutch plate warpage • Push lever shaft "1" Out of specification → Replace clutch plate • Copper washer "2" as a set. • Bolt (push lever shaft) "3" Use a surface plate "1"...
  • Page 127 CLUTCH 2. Install: 4. Bend the lock washer "1" tab. • Thrust washer [D=ø44 mm (1.73 in)] "1" • Clutch boss "2" 5. Install: • Friction plate "1" 3. Install: • Clutch plate "2" • Lock washer "1" • Nut (clutch boss) "2" •...
  • Page 128 CLUTCH 7. Install: 10.Install: • Push rod 2 "1" • O-ring "1" • Push rod 1 "2" To clutch cover. • Apply the transmission oil on the ends of the push rod 2. • Install the push rod 2 with its smaller end "a" toward you.
  • Page 129 KICK SHAFT AND SHIFT SHAFT KICK SHAFT AND SHIFT SHAFT REMOVING THE PRIMARY DRIVE GEAR 30 Nm (3.0 m kg, 22 ft lb) 10 Nm (1.0 m kg, 7.2 ft lb) 55 Nm (5.5 m kg, 40 ft lb) Order Part name Q'ty Remarks...
  • Page 130 KICK SHAFT AND SHIFT SHAFT REMOVING THE KICK SHAFT AND SHIFT SHAFT 10 Nm (1.0 m kg, 7.2 ft lb) 10 Nm (1.0 m kg, 7.2 ft lb) 10 Nm (1.0 m kg, 7.2 ft lb) 12 Nm (1.2 m kg, 8.7 ft lb) Order Part name Q'ty...
  • Page 131 KICK SHAFT AND SHIFT SHAFT REMOVING THE PRIMARY DRIVE GEAR REMOVING THE SEGMENT 1. Loosen: 1. Remove: • Bolt (primary drive gear) "1" • Bolt (segment) "1" • Segment "2" Place an aluminum plate "a" between the teeth of the primary drive gear "2" and driven gear Turn the segment counterclockwise until it "3".
  • Page 132 KICK SHAFT AND SHIFT SHAFT CHECKING THE KICK GEAR, KICK IDLE GEAR AND RATCHET WHEEL 1. Inspect: • Kick gear "1" • Kick idle gear "2" • Ratchet wheel "3" • Gear teeth "a" • Ratchet teeth "b" Wear/damage → Replace. CHECKING THE STOPPER LEVER 1.
  • Page 133 KICK SHAFT AND SHIFT SHAFT INSTALLING THE SEGMENT 1. Install: • Segment "1" • Bolt (segment) Bolt (segment): 30 Nm (3.0 m•kg, 22 ft•lb) Align the notch "a" on the segment with the pin "b" on the shift cam. INSTALLING THE SHIFT GUIDE AND SHIFT LEVER ASSEMBLY If the segment gets an impact, the stopper 1.
  • Page 134 KICK SHAFT AND SHIFT SHAFT INSTALLING THE KICK SHAFT ASSEMBLY 1. Install: • Kick gear "1" • Washer "2" • Circlip "3" • Ratchet wheel "4" • Spring "5" • Washer "6" • Circlip "7" To kick shaft "8". 4. Install: •...
  • Page 135 KICK SHAFT AND SHIFT SHAFT INSTALLING THE KICK IDLE GEAR 1. Install: • Kick idle gear "1" • Washer "2" • Circlip "3" • Apply the transmission oil on the kick idle gear inner circumference. • Install the kick idle gear with its depressed side "a"...
  • Page 136 KICK SHAFT AND SHIFT SHAFT Place an aluminum plate "a" between the teeth of the primary drive gear "2" and driven gear "3". 7. Install: • Kickstarter "1" • Washer "2" • Bolt (kickstarter) "3" Bolt (kickstarter): 4. Install: 30 Nm (3.0 m•kg, 22 ft•lb) •...
  • Page 137 YPVS GOVERNOR YPVS GOVERNOR REMOVING THE YPVS GOVERNOR Order Part name Q'ty Remarks Refer to "KICK SHAFT AND SHIFT Crankcase cover (right) SHAFT" section. Governor assembly Dowel pin Refer to removal section. Retainer Ball Retainer weight Washer Thrust bearing Collar Plate Compression spring Governor gear...
  • Page 138 YPVS GOVERNOR REMOVING THE GOVERNOR INSTALLING THE GOVERNOR 1. Remove: 1. Install: • Dowel pin "1" • Governor gear "1" • Compression spring "2" • Plate "3" While compressing the spring, remove the • Washer "4" dowel pin. • Thrust bearing "5" •...
  • Page 139 YPVS GOVERNOR 3. Install: • Dowel pin "1" • While compressing the spring, install the dow- el pin. • Make sure the dowel pin fits into the groove "a" in the retainer. 4. Install: • Governor assembly "1" Align the groove "a" in the governor with the fork "b"...
  • Page 140 WATER PUMP WATER PUMP DISASSEMBLING THE WATER PUMP 10 Nm (1.0 m kg, 7.2 ft lb) 14 Nm (1.4 m kg, 10 ft lb) 10 Nm (1.0 m kg, 7.2 ft lb) Order Part name Q'ty Remarks Refer to "KICK SHAFT AND SHIFT Crankcase cover (right) SHAFT"...
  • Page 141 WATER PUMP REMOVING THE IMPELLER SHAFT CHECKING THE IMPELLER SHAFT 1. Remove: 1. Inspect: • Impeller "1" • Impeller shaft "1" Bend/wear/damage → Replace. • Washer "2" Fur deposits → Clean. • Impeller shaft "3" Hold the impeller shaft on its width across the flats "a"...
  • Page 142 WATER PUMP CHECKING THE OIL SEAL INSTALLING THE IMPELLER SHAFT 1. Inspect: 1. Install: • Oil seal "1" • Impeller shaft "1" Wear/damage → Replace. • Take care so that the oil seal lip is not dam- aged or the spring does not slip off its posi- tion.
  • Page 143 WATER PUMP 3. Install: • Dowel pin "1" • Gasket (water pump housing cover) "2" 4. Install: • Water pump housing cover "1" • Bolt (water pump housing cover) "2" Bolt (water pump housing cover): 10 Nm (1.0 m•kg, 7.2 ft•lb) •...
  • Page 144 CDI MAGNETO CDI MAGNETO REMOVING THE CDI MAGNETO 7 Nm (0.7 m kg, 5.1 ft lb) 5 Nm (0.5 m kg, 3.6 ft lb) 56 Nm (5.6 m kg, 40 ft lb) Order Part name Q'ty Remarks Refer to "SEAT, FUEL TANK AND Seat and fuel tank SIDE COVERS"...
  • Page 145 CDI MAGNETO REMOVING THE ROTOR 1. Remove: • Nut (rotor) "1" • Washer "2" Use the rotor holding tool "3". Rotor holding tool: YU-01235/90890-01235 CHECKING THE WOODRUFF KEY 1. Inspect: • Woodruff key "1" Damage → Replace. 2. Remove: • Rotor "1" Use the flywheel puller "2".
  • Page 146 CDI MAGNETO 2. Install: • Woodruff key "1" • Rotor "2" • Clean the tapered portions of the crankshaft and rotor. • When installing the woodruff key, make sure that its flat surface "a" is in parallel with the crankshaft center line "b". •...
  • Page 147 ENGINE REMOVAL ENGINE REMOVAL REMOVING THE ENGINE 34 Nm (3.4 m kg, 24 ft lb) 64 Nm (6.4 m kg, 46 ft lb) 26 Nm (2.6 m kg, 19 ft lb) 85 Nm (8.5 m kg, 61 ft lb) 64 Nm (6.4 m kg, 46 ft lb) 5 Nm (0.5 m kg, 3.6 ft lb) 75 Nm (7.5 m kg, 54 ft lb) 4 Nm (0.4 m kg, 2.9 ft lb)
  • Page 148 ENGINE REMOVAL 34 Nm (3.4 m kg, 24 ft lb) 64 Nm (6.4 m kg, 46 ft lb) 26 Nm (2.6 m kg, 19 ft lb) 85 Nm (8.5 m kg, 61 ft lb) 64 Nm (6.4 m kg, 46 ft lb) 5 Nm (0.5 m kg, 3.6 ft lb) 75 Nm (7.5 m kg, 54 ft lb) 4 Nm (0.4 m kg, 2.9 ft lb)
  • Page 149 ENGINE REMOVAL HANDLING NOTE Support the machine securely so there is no danger of it falling over. REMOVING THE DRIVE SPROCKET 1. Remove: • Nut (drive sprocket) "1" • Lock washer "2" 2. Remove the engine "1" aslant and upward •...
  • Page 150 ENGINE REMOVAL Apply the molybdenum disulfide grease on the Install the drive sprocket together with the drive chain. pivot shaft. 2. Install: • Lock washer "1" • Nut (drive sprocket) "2" Nut (drive sprocket): 75 Nm (7.5 m•kg, 54 ft•lb) Tighten the nut while applying the rear brake.
  • Page 151 CRANKCASE AND CRANKSHAFT CRANKCASE AND CRANKSHAFT REMOVING THE CRANKSHAFT 14 Nm (1.4 m kg, 10 ft lb) 10 Nm (1.0 m kg, 7.2 ft lb) 30 Nm (3.0 m kg, 22 ft lb) 10 Nm (1.0 m kg, 7.2 ft lb) 10 Nm (1.0 m kg, 7.2 ft lb) Order Part name...
  • Page 152 CRANKCASE AND CRANKSHAFT 14 Nm (1.4 m kg, 10 ft lb) 10 Nm (1.0 m kg, 7.2 ft lb) 30 Nm (3.0 m kg, 22 ft lb) 10 Nm (1.0 m kg, 7.2 ft lb) 10 Nm (1.0 m kg, 7.2 ft lb) Order Part name Q'ty...
  • Page 153 CRANKCASE AND CRANKSHAFT REMOVING THE SEGMENT 1. Remove: • Bolt (segment) "1" 100 mm • Segment "2" Turn the segment counterclockwise until it stops and loosen the bolt. If the segment gets an impact, the stopper REMOVING THE CRANKSHAFT lever may be damaged. Take care not to 1.
  • Page 154 CRANKCASE AND CRANKSHAFT 3. Inspect: • Oil seal "1" Damage → Replace. CHECKING THE CRANKSHAFT 1. Measure: • Runout limit "a" • Small end free play limit "b" • Connecting rod big end side clearance "c" • Crank width "d" Out of specification →...
  • Page 155 CRANKCASE AND CRANKSHAFT INSTALLING THE CRANKSHAFT 1. Install: • Crankshaft "1" Use the crankshaft installing tools "2", "3", "4". Crankshaft installer pot "2": YU-90058/90890-01274 Crankshaft installer bolt "3": YU-90060/90890-01275 Adapter (M12) "4": INSTALLING THE CRANKCASE BEARING YU-90063/90890-01278 1. Install: • Bearing "1" •...
  • Page 156 3. Install: • O-ring "1" To right crankcase "2". 4. Apply: • Sealant On the right crankcase "1" Yamaha bond No.1215: 90890-85505 (Three bond No.1215®) 6. Install: • Holder "1" Clean the contacting surface of left and right • Bolt (holder) "2"...
  • Page 157 CRANKCASE AND CRANKSHAFT 7. Install: • Tension spring "1" • Holder "2" • Bolt (holder) "3" Bolt (holder): 10 Nm (1.0 m•kg, 7.2 ft•lb) Install the holder so that it contacts the projec- tion "a" on the right crankcase. 9. Remove: •...
  • Page 158 TRANSMISSION, SHIFT CAM AND SHIFT FORK TRANSMISSION, SHIFT CAM AND SHIFT FORK REMOVING THE TRANSMISSION, SHIFT CAM AND SHIFT FORK Order Part name Q'ty Remarks Refer to "ENGINE REMOVAL" sec- Engine tion. Refer to "CRANKCASE AND Separate the crankcase. CRANKSHAFT" section. Main axle Refer to removal section.
  • Page 159 TRANSMISSION, SHIFT CAM AND SHIFT FORK REMOVING THE TRANSMISSION 2. Inspect: 1. Remove: • O-ring "1" Damage → Replace. • Main axle "1" • Drive axle "2" • Shift cam • Shift fork 3 • Shift fork 2 • Shift fork 1 •...
  • Page 160 3. Check: • Shift fork movement Unsmooth operation → Replace shift fork. 2. Install: • 2nd wheel gear (23T) "1" • 4th wheel gear (24T/YZ250) (21T/YZ250X) "2" • 3rd wheel gear (23T/YZ250) (21T/YZ250X) "3" • 5th wheel gear (20T/YZ250) (21T/YZ250X) "4"...
  • Page 161 TRANSMISSION, SHIFT CAM AND SHIFT FORK 3. Install: 5. Install: • Washer "1" • Shift fork 1 (L) "1" • Circlip "2" • Shift fork 2 (C10) "2" • Shift fork 3 (R) "3" • Shift cam "4" • Be sure the circlip sharp-edged corner "a" is To main axle and drive axle.
  • Page 162 TRANSMISSION, SHIFT CAM AND SHIFT FORK 6. Install: • Transmission assembly "1" To left crankcase "2". Apply the transmission oil on the bearings and guide bars. 7. Check: • Shifter operation • Transmission operation Unsmooth operation → Repair. 4-71 Downloaded from ManualsNet.com search engine...
  • Page 163 This section is intended for those who have basic knowledge and skill concerning the servicing of Yamaha motorcycles (e.g., Yamaha dealers, service engineers, etc.) Those who have little knowl- edge and skill concerning servicing are requested not to undertake inspection, adjustment, disas- sembly, or reassembly only by reference to this manual.
  • Page 164 FRONT WHEEL AND REAR WHEEL Order Part name Q'ty Remarks Bearing Refer to removal section. Brake disc Downloaded from ManualsNet.com search engine...
  • Page 165 FRONT WHEEL AND REAR WHEEL REMOVING THE REAR WHEEL Order Part name Q'ty Remarks Hold the machine by placing the suit- Refer to "HANDLING NOTE". able stand under the engine. Nut (rear wheel axle) Rear wheel axle Drive chain puller Rear wheel Refer to removal section.
  • Page 166 FRONT WHEEL AND REAR WHEEL HANDLING NOTE Support the machine securely so there is no danger of it falling over. REMOVING THE REAR WHEEL 1. Remove: • Wheel "1" Push the wheel forward and remove the drive 2. Inspect: chain "2". •...
  • Page 167 FRONT WHEEL AND REAR WHEEL CHECKING THE BRAKE DISC • Use a socket that matches the outside diam- 1. Measure: eter of the race of the bearing. • Brake disc deflection (only rear brake disc) • Left side of bearing shall be installed first. Use the dial gauge "1".
  • Page 168 FRONT WHEEL AND REAR WHEEL 3. Install: 6. Install: • Collar "1" • Nut (wheel axle) "1" Nut (wheel axle): • Apply the lithium soap base grease on the oil 105 Nm (10.5 m•kg, 75 ft•lb) seal lip. • Install the collars with their projections "a" fac- ing the wheel.
  • Page 169 FRONT WHEEL AND REAR WHEEL • Apply the lithium soap base grease on the bearing and oil seal lip when installing. • Install the bearing with seal facing outward. • Use a socket that matches the outside diam- eter of the race of the bearing. •...
  • Page 170 FRONT WHEEL AND REAR WHEEL 5. Install: 8. Install: • Wheel • Right drive chain puller "1" • Washer "2" • Nut (wheel axle) "3" Install the brake disc "1" between the brake pads "2" correctly. Temporarily tighten the nut (wheel axle) at this point.
  • Page 171 FRONT BRAKE AND REAR BRAKE FRONT BRAKE AND REAR BRAKE REMOVING THE FRONT BRAKE Order Part name Q'ty Remarks Hold the machine by placing the suit- Refer to "HANDLING NOTE". able stand under the engine. Drain the brake fluid. Refer to removal section. Brake hose holder (protector) Union bolt Brake hose...
  • Page 172 FRONT BRAKE AND REAR BRAKE REMOVING THE REAR BRAKE Order Part name Q'ty Remarks Hold the machine by placing the suit- Refer to "HANDLING NOTE". able stand under the engine. Refer to "FRONT WHEEL AND Rear wheel REAR WHEEL" section. Drain the brake fluid.
  • Page 173 FRONT BRAKE AND REAR BRAKE DISASSEMBLING THE BRAKE CALIPER Order Part name Q'ty Remarks A. Front B. Rear Pad pin Brake pad Pad support Brake caliper piston 1 Refer to removal section. Brake caliper piston dust seal 1 Refer to removal section. Brake caliper piston seal 1 Refer to removal section.
  • Page 174 FRONT BRAKE AND REAR BRAKE DISASSEMBLING THE BRAKE MASTER CYLINDER Order Part name Q'ty Remarks A. Front B. Rear Brake master cylinder cap Diaphragm Reservoir float Push rod (Front) Brake master cylinder boot Circlip Use a long nose circlip pliers. Washer Push rod (Rear) Brake master cylinder kit...
  • Page 175 FRONT BRAKE AND REAR BRAKE HANDLING NOTE • Do not reuse the drained brake fluid. Support the machine securely so there is no • Brake fluid may erode painted surfaces or danger of it falling over. plastic parts. Always clean up spilled fluid immediately.
  • Page 176 FRONT BRAKE AND REAR BRAKE REMOVING THE BRAKE CALIPER PISTON SEAL KIT 1. Remove: • Brake caliper piston dust seal "1" • Brake caliper piston seal "2" Remove the brake caliper piston seals and brake caliper piston dust seals by pushing them with a finger.
  • Page 177 FRONT BRAKE AND REAR BRAKE CHECKING THE BRAKE CALIPER HANDLING NOTE 1. Inspect: • Brake caliper cylinder inner surface "a" • All internal parts should be cleaned in new Wear/score marks → Replace brake caliper brake fluid only. assembly. • Internal parts should be lubricated with brake fluid when installed.
  • Page 178 FRONT BRAKE AND REAR BRAKE • Install the brake pads with their projections "a" into the brake caliper recesses "b". • Temporarily tighten the pad pin at this point. A. Front B. Rear 3. Install: • Brake caliper piston "1" 2.
  • Page 179 FRONT BRAKE AND REAR BRAKE INSTALLING THE BRAKE MASTER CYLINDER KIT 1. Clean: • Brake master cylinder • Brake master cylinder kit Clean them with brake fluid. 2. Install: • Brake master cylinder cup (primary) "1" • Brake master cylinder cup (secondary) "2" To brake master cylinder piston "3".
  • Page 180 FRONT BRAKE AND REAR BRAKE INSTALLING THE FRONT BRAKE MASTER CYLINDER 1. Install: • Brake master cylinder "1" • Brake master cylinder bracket "2" • Bolt (brake master cylinder bracket) "3" Bolt (brake master cylinder brack- et): 9 Nm (0.9 m•kg, 6.5 ft•lb) 4.
  • Page 181 FRONT BRAKE AND REAR BRAKE INSTALLING THE REAR BRAKE MASTER CYLINDER 1. Install: • Copper washer "1" • Brake hose "2" • Union bolt "3" Union bolt: 30 Nm (3.0 m•kg, 22 ft•lb) 3. Install: Always use new copper washers. •...
  • Page 182 FRONT BRAKE AND REAR BRAKE INSTALLING THE FRONT BRAKE HOSE 1. Install: • Copper washer "1" • Brake hose "2" • Union bolt "3" Union bolt: 30 Nm (3.0 m•kg, 22 ft•lb) Always use new copper washers. 3. Pass the brake hose through the cable guide "1".
  • Page 183 FRONT BRAKE AND REAR BRAKE After installing the brake hose holders, make sure the brake hose does not contact the spring (rear shock absorber). If it does, correct its twist. INSTALLING THE REAR BRAKE HOSE 1. Install: • Copper washer "1" •...
  • Page 184 FRONT BRAKE AND REAR BRAKE Brake fluid may erode painted surfaces or After installation, while pulling the brake le- plastic parts. Always clean up spilled fluid ver in or pushing down on the brake pedal, immediately. check whether there is any brake fluid leak- ing where the union bolts are installed re- spectively at the brake master cylinder and brake caliper.
  • Page 185 FRONT FORK FRONT FORK REMOVING THE FRONT FORK Order Part name Q'ty Remarks Hold the machine by placing the suit- Refer to "HANDLING NOTE". able stand under the engine. Refer to "FRONT WHEEL AND Front wheel REAR WHEEL" section. Refer to "FRONT BRAKE AND Front brake caliper REAR BRAKE"...
  • Page 186 FRONT FORK DISASSEMBLING THE FRONT FORK 30 Nm (3.0 m kg, 22 ft lb) 29 Nm (2.9 m kg, 21 ft lb) 1 Nm (0.1 m kg, 0.7 ft lb) 29 Nm (2.9 m kg, 21 ft lb) 55 Nm (5.5 m kg, 40 ft lb) Order Part name Q'ty...
  • Page 187 FRONT FORK HANDLING NOTE REMOVING THE ADJUSTER 1. Drain the outer tube of its front fork oil at its top. Support the machine securely so there is no 2. Loosen: danger of it falling over. • Adjuster "1" The front fork requires careful attention. So it is recommended that the front fork be maintained at the dealers.
  • Page 188 FRONT FORK 2. Remove: CHECKING THE DAMPER ASSEMBLY • Inner tube "1" 1. Inspect: • Damper assembly "1" Bend/damage → Replace. Oil seal removal steps: • O-ring "2" a. Push in slowly "a" the inner tube just before Wear/damage → Replace. it bottoms out and then pull it back quickly "b".
  • Page 189 FRONT FORK Inner tube bending limit: 0.2 mm (0.01 in) The bending value is shown by one half of the dial gauge reading. Do not attempt to straighten a bent inner tube as this may dangerously weaken the CHECKING THE COLLAR tube.
  • Page 190 3. Fill: assembly. • Front fork oil "1" To damper assembly. Recommended oil: Yamaha Suspension Oil S1 Oil capacity: 205 cm (7.21 Imp oz, 6.93 US oz) • Be sure to use recommended fork oil. If other oils are used, they may have an ex- cessively adverse effect on the front fork performance.
  • Page 191 FRONT FORK 8. Install: 11.After filling, pump the damper assembly "1" • Base valve "1" slowly up and down more than 10 times to To damper assembly "2". distribute the fork oil. First bring the damper rod pressure to a maxi- mum.
  • Page 192 FRONT FORK 14.Check: 16.Install: • Damper assembly smooth movement • Piston metal "1" Tightness/binding/rough spots → Repeat the steps 2 to 13. Install the piston metal onto the slot on inner tube. 15.Install: • Dust seal "1" 17.Install: • Stopper ring "2" •...
  • Page 193 FRONT FORK 21.Install: • Dust seal "1" Apply the lithium soap base grease on the inner tube. 19.Install: • Oil seal "1" Press the oil seal into the outer tube with fork seal driver "2". 22.Check: Fork seal driver: • Inner tube smooth movement YM-A0948/90890-01502 Tightness/binding/rough spots →...
  • Page 194 FRONT FORK 26.Loosen: • Rebound damping adjuster "1" • Loosen the rebound damping adjuster finger tight. • Record the set position of the adjuster (the amount of turning out the fully turned in posi- tion). 24.Install: • Collar "1" • Fork spring "2" To damper assembly "3".
  • Page 195 • Front fork oil "1" If the adjuster is installed out of specification, From outer tube top. proper damping force cannot be obtained. Recommended oil: Yamaha Suspension Oil S1 Standard oil amount: 320 cm (11.3 Imp oz, 10.8 US oz) Extent of adjustment: 300–365 cm...
  • Page 196 FRONT FORK 33.Install: 3. Adjust: • Protector guide "1" • Front fork top end "a" Front fork top end (standard) "a": YZ250: 0 mm (0 in) YZ250X: 0 mm (0 in) *5 mm (0.2 in) *For AUS INSTALLING THE FRONT FORK 1.
  • Page 197 FRONT FORK 6. Adjust: • Rebound damping force Turn in the damping adjuster "1" finger-tight and then turn out to the originally set position. 7. Adjust: • Compression damping force Turn in the damping adjuster "1" finger-tight and then turn out to the originally set position. 5-35 Downloaded from ManualsNet.com...
  • Page 198 HANDLEBAR HANDLEBAR REMOVING THE HANDLEBAR 0.5 Nm (0.05 m kg, 0.36 ft lb) 9 Nm (0.9 m kg, 6.5 ft lb) 28 Nm (2.8 m kg, 20 ft lb) 5 Nm (0.5 m kg, 3.6 ft lb) 4 Nm (0.4 m kg, 2.9 ft lb) 0.5 Nm (0.05 m kg, 0.36 ft lb) 40 Nm (4.0 m kg, 29 ft lb) 4 Nm (0.4 m kg, 2.9 ft lb)
  • Page 199 HANDLEBAR DISASSEMBLING THE THROTTLE Order Part name Q'ty Remarks Grip cap (lower) Grip cap (upper) Grip assembly Grip (right) Refer to removal section. Tube guide 5-37 Downloaded from ManualsNet.com search engine...
  • Page 200 HANDLEBAR REMOVING THE BRAKE MASTER CYLINDER 1. Remove: • Brake master cylinder bracket "1" • Brake master cylinder "2" • Do not let the brake master cylinder hang on the brake hose. • Keep the brake master cylinder cap side horizontal to prevent air from coming in.
  • Page 201 HANDLEBAR 2. Install: • Handlebar "1" • Upper handlebar holder "2" • Bolt (upper handlebar holder) "3" Bolt (upper handlebar holder): 28 Nm (2.8 m•kg, 20 ft•lb) • The upper handlebar holders should be in- stalled with the punch marks "a" facing for- ward.
  • Page 202 HANDLEBAR • Tighten the grip cap bolts temporarily without the throttle being fixed to the handlebar. 3. Tighten: • Nut (lower handlebar holder) "1" Nut (lower handlebar holder): 6. Install: 40 Nm (4.0 m•kg, 29 ft•lb) • Throttle cables "1" To tube guide "2".
  • Page 203 HANDLEBAR 8. Install: • Throttle cable cap "1" • Screw (throttle cable cap) "2" Screw (throttle cable cap): 0.5 Nm (0.05 m•kg, 0.36 ft•lb) 12.Install: • Bolt (grip cap) "1" Bolt (grip cap): 4 Nm (0.4 m•kg, 2.9 ft•lb) 9. Adjust: •...
  • Page 204 HANDLEBAR • Clamp "4" • The engine stop switch, clutch lever holder and clamp should be installed according to the dimensions shown. • Pass the engine stop switch lead in the middle of the clutch lever holder. 0 mm (0 in) 0 mm (0 in) 14.Install:...
  • Page 205 STEERING STEERING REMOVING THE STEERING Order Part name Q'ty Remarks TIGHTENING STEPS: • Tighten ring nut. 38 Nm (3.8 m•kg, 27 ft•lb) • Loosen it one turn. • Retighten it. 7 Nm (0.7 m•kg, 5.1 ft•lb) Hold the machine by placing the suit- Refer to "HANDLING NOTE".
  • Page 206 STEERING Order Part name Q'ty Remarks Steering ring nut Refer to removal section. Lower bracket Bearing race cover Upper bearing Lower bearing Refer to removal section. Bearing race Refer to removal section. 5-44 Downloaded from ManualsNet.com search engine...
  • Page 207 STEERING HANDLING NOTE REMOVING THE BEARING RACE 1. Remove: • Bearing race "1" Support the machine securely so there is no Remove the bearing race using long rod "2" danger of it falling over. and the hammer. REMOVING THE STEERING RING NUT 1.
  • Page 208 STEERING INSTALLING THE LOWER BRACKET 4. Install: 1. Install: • Steering ring nut "1" • Lower bearing "1" Steering ring nut: 7 Nm (0.7 m•kg, 5.1 ft•lb) Apply the lithium soap base grease on the dust Tighten the steering ring nut using the steer- seal lip and bearing inner circumference.
  • Page 209 10.Adjust: • Front fork "1" • Front fork top end "a" • Upper bracket "2" Front fork top end (standard) "a": YZ250: • Temporarily tighten the pinch bolts (lower 0 mm (0 in) bracket). YZ250X: • Do not tighten the pinch bolts (upper bracket) 0 mm (0 in) yet.
  • Page 210 SWINGARM SWINGARM REMOVING THE SWINGARM Order Part name Q'ty Remarks Hold the machine by placing the suit- Refer to "HANDLING NOTE". able stand under the engine. Refer to "FRONT BRAKE AND Brake hose holder REAR BRAKE" section. Refer to "FRONT BRAKE AND Rear brake caliper REAR BRAKE"...
  • Page 211 SWINGARM DISASSEMBLING THE SWINGARM Order Part name Q'ty Remarks Refer to removal section. Relay arm Connecting rod Collar Oil seal Thrust bearing Bushing Oil seal Bearing Refer to removal section. 5-49 Downloaded from ManualsNet.com search engine...
  • Page 212 SWINGARM HANDLING NOTE Support the machine securely so there is no danger of it falling over. REMOVING THE CAP 1. Remove: • Left cap "1" Remove with a slotted-head screwdriver insert- CHECKING THE RELAY ARM ed under the mark "a" on the left cap. 1.
  • Page 213 SWINGARM INSTALLING THE BEARING AND OIL SEAL 1. Install: • Bearing "1" • Oil seal "2" To swingarm. • Apply the molybdenum disulfide grease on the bearing when installing. • Install the bearing by pressing it on the side having the manufacture's marks or numbers. •...
  • Page 214 SWINGARM INSTALLING THE SWINGARM 1. Install: • Bushing "1" • Thrust bearing "2" • Oil seal "3" • Collar "4" To swingarm "5". Apply the molybdenum disulfide grease on the bushings, thrust bearings, oil seal lips and con- tact surfaces of the collar and thrust bearing. 4.
  • Page 215 SWINGARM • Apply the molybdenum disulfide grease on the bolt. • Do not tighten the nut yet. 6. Install: • Swingarm "1" • Pivot shaft "2" Pivot shaft: 85 Nm (8.5 m•kg, 61 ft•lb) 9. Install: • Bolt (rear shock absorber-relay arm) "1" •...
  • Page 216 SWINGARM 11.Tighten: • Nut (relay arm) "1" Nut (relay arm): 70 Nm (7.0 m•kg, 50 ft•lb) A. YZ250 B. YZ250X 14.Install: • Drive chain support "1" • Drive chain support cover "2" 12.Install: • Bolt {drive chain support [L = 50 mm (1.97 •...
  • Page 217 REAR SHOCK ABSORBER REAR SHOCK ABSORBER REMOVING THE REAR SHOCK ABSORBER 56 Nm (5.6 m kg, 40 ft lb) 32 Nm (3.2 m kg, 23 ft lb) 29 Nm (2.9 m kg, 21 ft lb) 53 Nm (5.3 m kg, 38 ft lb) Order Part name Q'ty...
  • Page 218 REAR SHOCK ABSORBER 56 Nm (5.6 m kg, 40 ft lb) 32 Nm (3.2 m kg, 23 ft lb) 29 Nm (2.9 m kg, 21 ft lb) 53 Nm (5.3 m kg, 38 ft lb) Order Part name Q'ty Remarks Lower spring guide Upper spring guide Spring (rear shock absorber)
  • Page 219 Wear eye protection to prevent eye damage from escaping gas and/or metal chips. To dispose of a damaged or worn-out rear shock absorber, take the unit to your Yamaha dealer for this disposal procedure. 5-57 Downloaded from ManualsNet.com search engine...
  • Page 220 REAR SHOCK ABSORBER CHECKING THE REAR SHOCK ABSORBER 1. Inspect: • Damper rod "1" Bends/damage → Replace rear shock ab- sorber assembly. • Shock absorber "2" Oil leaks → Replace rear shock absorber as- sembly. Gas leaks → Replace rear shock absorber assembly.
  • Page 221 REAR SHOCK ABSORBER INSTALLING THE SPRING (REAR SHOCK INSTALLING THE REAR SHOCK ABSORBER) ABSORBER 1. Install: 1. Install: • Spring "1" • Dust seal "1" • Upper spring guide "2" • O-ring "2" • Lower spring guide "3" • Collar "3" •...
  • Page 222 REAR SHOCK ABSORBER 4. Install: • Bolt (rear shock absorber-frame) "1" • Washer "2" • Nut (rear shock absorber-frame) "3" Nut (rear shock absorber-frame): 56 Nm (5.6 m•kg, 40 ft•lb) Apply the molybdenum disulfide grease on the bolt. 7. Tighten: •...
  • Page 223 This section is intended for those who have basic knowledge and skill concerning the servicing of Yamaha motorcycles (e.g., Yamaha dealers, service engineers, etc.) Those who have little knowl- edge and skill concerning servicing are requested not to undertake inspection, adjustment, disas- sembly, or reassembly only by reference to this manual.
  • Page 224 ELECTRICAL COMPONENTS AND WIRING DIAGRAM WIRING DIAGRAM 1. CDI unit 2. Engine stop switch 3. Ignition coil 4. Throttle position sensor 5. Solenoid valve 6. Neutral switch 7. CDI magneto 8. Spark plug COLOR CODE Black Blue Orange Sky blue Yellow Black/Blue Black/Red...
  • Page 225 IGNITION SYSTEM IGNITION SYSTEM INSPECTION STEPS Use the following steps for checking the possibility of the malfunctioning engine being attributable to ignition system failure and for checking the spark plug which will not spark. Spark → Spark gap test *Clean or replace spark plug. No spark ↓...
  • Page 226 IGNITION SYSTEM SPARK GAP TEST CHECKING THE ENGINE STOP SWITCH 1. Disconnect the spark plug cap from spark 1. Inspect: plug. • Engine stop switch conduction 2. Connect the dynamic spark tester "1" (igni- Tester (+) lead → Black/White lead "1" tion checker "2") as shown.
  • Page 227 IGNITION SYSTEM Secondary coil Tester selector resistance position 9.52–14.28 kΩat kΩ × 1 20 °C (68 °F) • Remove the spark plug cap by turning it coun- terclockwise and inspect. • Install the spark plug cap by turning it clock- wise until it is tight.
  • Page 228 IGNITION SYSTEM 3. Inspect: • Charging coil 2 resistance Out of specification → Replace. Tester (+) lead → Green/Blue lead "1" Tester (-) lead → Green/White lead "2" Charging coil 2 Tester selector resistance position 44.0–66.0 Ω at Ω × 10 20 °C (68 °F) CHECKING THE NEUTRAL SWITCH 1.
  • Page 229 SOLENOID VALVE SYSTEM SOLENOID VALVE SYSTEM INSPECTION STEPS If the solenoid valve will not operate, use the following inspection steps. No good → Check each couplers and wire connec- Repair or replace. tion. OK ↓ No good → Check solenoid valve. (Check solenoid Replace.
  • Page 230 SOLENOID VALVE SYSTEM CHECKING THE COUPLERS AND LEADS CONNECTION 1. Check: • Couplers and leads connection Rust/ Dust/ Looseness/Short-circuit → Re- pair or replace. CHECKING THE SOLENOID VALVE OPERATION 1. Disconnect the solenoid valve coupler. 2. Connect 12V battery to the solenoid valve coupler.
  • Page 231 THROTTLE POSITION SENSOR SYSTEM THROTTLE POSITION SENSOR SYSTEM INSPECTION STEPS If the throttle position sensor will not operate, use the following inspection steps. No good → Check entire ignition system for connec- Repair or replace. tion. OK ↓ No good → Check throttle position sensor.
  • Page 232 THROTTLE POSITION SENSOR SYSTEM HANDLING NOTE 3. Inspect: • Throttle position sensor coil variable resis- tance Do not loosen the screw (throttle position Check that the resistance in increased as sensor) "1" except when changing the the lever "1" is moved from the full close po- throttle position sensor due to failure be- sition to the full open position.
  • Page 233 THROTTLE POSITION SENSOR SYSTEM 3. Replace: 7. Insert the thin electric conductors "2" (lead • Throttle position sensor wire) into the throttle position sensor coupler 4. Install: "1", as shown, and connect the tester to • Throttle position sensor "1" them.
  • Page 234 THROTTLE POSITION SENSOR SYSTEM 10.Put the aligning marks "a" on the throttle po- Throttle position Tester selector sition sensor and carburetor. sensor input position voltage 4–6 V DCV-20 11.Stop the engine. 12.Remove: • Carburetor Refer to "CARBURETOR AND REED VALVE" section in the CHAPTER 4. 13.Tighten: •...

  • Page 235: Tuning

    ENGINE TUNING • Lower atmospheric pressure (at a high alti- tude) reduces the density of the air. ENGINE TEST RUN CARBURETOR SETTING After warming up the engine equipped with the • The role of fuel is to cool the engine, and in standard type carburetor(s) and spark plug(s), the case of a 2-stroke engine, to lubricate the run two or three laps of the circuit and check the...
  • Page 236 ENGINE EFFECT OF SETTING PARTS IN RELATION TO THROTTLE VALVE OPENING ADJUSTING THE POWER JET The richness of air-fuel mixture under 8,500 rpm to the extent of 1/2 to full opened throttle can be set by changing the power jet "1". A larg- er size jet results in a richer mixture, and a smaller size in a leaner mixture.
  • Page 237 *#52 * Except for USA and CAN ADJUSTING THE JET NEEDLE On the carburetors used in the YZ250/YZ250X, the main nozzle is press-fitted, so it can not be replaced. Therefore, carburetor setting re- quires the change of the jet needle.
  • Page 238 ENGINE 2. Effects of changing the jet needle (refer- RELATIONSHIP WITH THROTTLE OPENING ence) The flow of the fuel through the carburetor main • Diameter of straight portion system is controlled by the main jet and then, it Changing the diameter of the straight por- is further regulated by the area between the tion adjusts the air-fuel mixture when the main nozzle and the jet needle.
  • Page 239 ENGINE CARBURETOR SETTING PARTS Part name Size Part number Main jet Rich #190 4MX-14943-45 "1" #188 4MX-14943-95 #185 4MX-14943-44 #182 4MX-14943-94 *(STD) #180 4MX-14943-43 (STD) #178 4MX-14943-93 #175 4MX-14943-42 #172 4MX-14943-92 #170 4MX-14943-41 #168 4MX-14943-91 #165 4MX-14943-40 Lean #162 4MX-14943-90 Pilot jet Rich 4MX-14948-12...
  • Page 240 ENGINE ROAD CONDITION AND EXAMPLES OF CARBURETOR SETTING General condition Sandy condition Under 10°C 15–25°C Over 25°C Under 10°C 15–25°C Over 25°C (50°F) (59–77°F) (77°F) (50°F) (59–77°F) (77°F) (Winter) (Spring, Au- (Summer) (Winter) (Spring, Au- (Summer) tumn) tumn) Main jet #178 #178 #178...
  • Page 241 ENGINE Symptom Setting Checking Lean mixture Lower jet needle clip position. (1 Groove 1 Clip groove down) Groove 2 Groove 3 Rich mixture Raise jet needle clip position. (1 Leaner Groove 4 Groove 5 groove up) (Standard) 1/4–3/4 throttle Lower jet needle clip position. (1 Hard breathing groove down) Richer...
  • Page 242 ENGINE CHANGE OF THE HEAT RANGE OF SPARK PLUGS Judging from the discoloration of spark plugs, if they are found improper, it can be corrected by the following two methods; changing carburetor settings and changing the heat range of spark plug.
  • Page 243 CHASSIS CHASSIS DRIVE AND REAR WHEEL SPROCKETS SETTING PARTS SELECTION OF THE SECONDARY REDUCTION RATIO (SPROCKET) Part name Size Part number Drive sprocket "1" Secondary reduction ratio = Number of rear wheel sprocket teeth/Number of 9383E-13216 drive sprocket teeth (STD) 9383E-14215 Standard secondary re- Rear wheel...
  • Page 244 CHASSIS • Under a stony or hard road condition, the tire pressure should be higher to prevent a flat tire. Extent of adjustment: 100–120 kPa (1.00–1.20 kgf/cm 15–18 psi) FRONT FORK SETTING The front fork setting should be made depend- ing on the rider's feeling of an actual run and the circuit conditions.
  • Page 245 CHASSIS 2. Use of stiff spring REAR SUSPENSION SETTING • Change the rebound damping. The rear suspension setting should be made Turn in one or two clicks. depending on the rider's feeling of an actual run • Change the compression damping. and the circuit conditions.
  • Page 246 CHASSIS Length "a" of standard shock: • If the machine is new and after it is broken in, 490 mm (19.29 in) the same set length of the spring may change because of the initial fatigue, etc. of the spring. Therefore, be sure to make reevalua- tion.
  • Page 247 CHASSIS • Extent of adjustment (spring preload) SPRING PART Maximum Minimum NUMBER (-22212-) 5UN-00 5UN-10 5UN-20 5UN-30 5UN-40 Position in Position in 5UN-50 which the which the 5UN-60 spring is spring is 5UN-70 turned in 18 turned in 1.5 mm (0.71 in) mm (0.06 in) 5UN-A0 from its free...
  • Page 248 CHASSIS SUSPENSION SETTING (FRONT FORK) • If any of the following symptoms is experienced with the standard position as the base, make reset- ting by reference to the adjustment procedure given in the same chart. • Before any change, set the rear shock absorber sunken length to the standard figure 90–100 mm (3.5–3.9 in).
  • Page 249 CHASSIS SUSPENSION SETTING (REAR SHOCK ABSORBER) • If any of the following symptoms is experienced with the standard position as the base, make reset- ting by reference to the adjustment procedure given in the same chart. • Adjust the rebound damping in 2-click increments or decrements. •...
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  • Page 251 For your best ownership experience, think Genuine Yamaha! Genuine Yamaha Parts – Genuine Yamaha replacement parts are the exact same parts as the ones originally equipped on your vehicle, providing you with the performance and durability you have come to expect.
  • Page 252 PRINTED ON RECYCLED PAPER PRINTED IN JAPAN 2017.04-0.7×1 !

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