Yamaha MZ250 Service Manual
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Yamaha MZ250 Service Manual

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SERVICE MANUAL
MZ250
MZ300
LIT-19616-01-80
7VB-F8197-10

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Summary of Contents for Yamaha MZ250

  • Page 1 SERVICE MANUAL MZ250 MZ300 LIT-19616-01-80 7VB-F8197-10...
  • Page 3 FOREWORD HOW TO USE THIS MANUAL PARTICULARLY IMPORTANT This manual was written by the Yamaha Motor Powered Products Co., Ltd. primarily for use INFORMATION by Yamaha dealers and their qualified mechan- ics. It is not possible to put an entire mechan- Particularly important information is distin- ic’s education into one manual, so it is...
  • Page 4 HOW TO USE THIS MANUAL This Service Manual contains general information on service procedure and data for the Multi- purpose engine. For complete information on service procedure and data, it is necessary to use this Service Manual together with the Supplementary Service Manual. Comprehensive explanations of all installation, removal, disassembly, assembly, repair and check procedures are laid out with the individual steps in sequential order.
  • Page 5 ILLUSTRATED SYMBOLS (Refer to the illustration) SYMBOL DEFINITION SYMBOL DEFINITION Periodic checks and General information adjustments Engine Carburetor Electrical Troubleshooting Specifications Filling fluid Lubricant Special tool Tightening torque Wear limit, clearance Engine speed Electrical data Replace the part with a new one. Lithium-soap base grease Molybdenum disulfide grease Engine oil...
  • Page 7 INDEX GENERAL INFORMATION INFO PERIODIC CHECKS AND ADJUSTMENTS ENGINE CARBURETOR CARB ELECTRICAL ELEC TROUBLESHOOTING TRBL...

  • Page 8: Table Of Contents

    CHAPTER 1. ADJUSTING THE ENGINE SPEED (WITH THROTTLE GENERAL INFORMATION LEVER MODEL) .........2-15 ADJUSTING THE ENGINE SPEED ...2-17 IMPORTANT INFORMATION ....1-1 RECOIL STARTER ......2-17 PREPARATION FOR REMOVAL AND FITTINGS AND FASTENERS ....2-17 DISASSEMBLY ........1-1 CAUTION ON SERVICE .......1-1 CHAPTER 3. NOTES ON SERVICE......1-1 ENGINE ALL REPLACEMENT PARTS ....1-2...
  • Page 9 INSTALLING THE FLYWEIGHT SELECTING THE CRANKSHAFT SHAFT ASSEMBLY AND SHIM (P.T.O. SHAFT TYPE E) ....3-48 GOVERNOR SHAFT ......3-19 CHAPTER 4. ENGINE SWITCH AND OIL WARNING CARBURETOR UNIT ............3-20 REMOVING THE CARBURETOR ....4-1 CYLINDER HEAD COVER, CYLINDER HEAD ............3-21 DISASSEMBLING THE CARBURETOR ...4-2 CHECKING THE ROCKER ARM ..3-23 MANUAL CHOKE MODEL ....4-2 CHECKING THE PUSH ROD .....3-23...
  • Page 10 CHAPTER 6. TROUBLESHOOTING ENGINE ............6-1...

  • Page 11: Chapter 1. General Information

    When servicing the engine, always keep the engine and your- self away from fire. NOTES ON SERVICE 1. Correct tools Be sure to use the correct special tool for the job to guard against damage. SVU1040 2. Oil, grease and seals Be sure to use genuine Yamaha oils, grease and sealers, or the equivalents. SVU1050 3. Expendable parts Always replace the gaskets, O-rings, cotter pins and circlips with new parts when servicing engine. SVU1060 4. Tightening torque Be sure to follow torque specifications. When tightening bolts,...

  • Page 12: All Replacement Parts

    IMPORTANT INFORMATION INFO ALL REPLACEMENT PARTS We recommend the use of genuine Yamaha parts for all replace- ments. Use oil and/or grease, recommended by Yamaha, for assembly and adjustment. GASKETS, OIL SEALS, AND O-RINGS 1. All gaskets, seals, and O-rings should be replaced when an engine is overhauled. All gaskets surfaces, oil seal lips, and...

  • Page 13: Basic Service Information

    BASIC SERVICE INFORMATION INFO BASIC SERVICE INFORMATION ELECTRICAL SYSTEM Checking the electrical system Before checking the electrical system, make sure that the battery voltage is at least 12 V. NOTICE Never insert the tester probes into the coupler terminal slots. Always insert the probes from the opposite end a of the cou- pler, taking care not to loosen or damage the leads.
  • Page 14 BASIC SERVICE INFORMATION INFO 2. Check: 9 Lead 9 Coupler 9 Connector Moisture → Dry with an air blower. Rust/stains → Connect and disconnect several times. 3. Check: 9 All connections Loose connection → Connect properly. 9 If the pin 1 on the terminal is flattened, bend it up. 9 After disassembling and assembling a coupler, pull on the leads to make sure that they are installed securely. 4. Connect: 9 Lead 9 Coupler 9 Connector 9 When connecting a coupler or connector, push both sections of the coupler or connector together until they are connected securely.
  • Page 15 BASIC SERVICE INFORMATION INFO 5. Check: 9 Continuity (with the pocket tester) Analog pocket tester: YU-03112-C Pocket tester: 90890-03112 9 If there is no continuity, clean the terminals. 9 When checking the wire harness, perform steps (1) to (4). 9 As a quick remedy, use a contact revitalizer available at most part stores.

  • Page 16: Special Tools And Testers

    SPECIAL TOOLS AND TESTERS INFO SPECIAL TOOLS AND TESTERS The proper special tools are necessary for complete and accurate tune-up and assembly. Using the correct special tool will help pre- vent damage caused by the use of improper tools or improvised techniques. 9 For U.S.A. and Canada, use part number starting with “YM-”, “YU-”, or “ACC-”. 9 For others, use part number starting with “90890-”. 1. Analog pocket tester P/N. YU-03112-C Pocket tester P/N. 90890-03112 This instrument is necessary for checking the electrical system.
  • Page 17 SPECIAL TOOLS AND TESTERS INFO 6. Extension P/N. 90890-04082 This tool is used for checking engine compression. 7. Primary clutch holder P/N. YS-01880-A Sheave holder P/N. 90890-01701 This tool is necessary for holding the magneto rotor. 8. Heavy duty puller P/N. YU-33270-B Flywheel puller P/N. 90890-01362 This tool is necessary for removing the magneto rotor. SVU1220 9. Valve spring compressor P/N. 90890-01253 This tool is used to remove the valve springs. 10. Cylinder gauge Commercially obtainable This instrument is used for checking cylinder bore size and condition. SVU1160 11. Dial indicator gauge P/N. YU-A8428 Dial gauge...

  • Page 18: Chapter 2. Periodic Checks And Adjustments

    INTRODUCTION/MAINTENANCE INTERVALS CHART/ PERIODIC MAINTENANCE/LUBRICATION INTERVALS PERIODIC CHECKS AND ADJUSTMENTS INTRODUCTION This chapter includes all information necessary to perform recommended checks and adjustments. These preventive maintenance procedures, if followed, will ensure more reliable machine operation and a longer service life. The need for costly overhaul work will be greatly reduced. This information applies to machines already in service as well as new machines that are being pre- pared for sale.
  • Page 19 *1····· The air filter element needs to be replaced more frequently when using in unusually wet or dusty areas. ····· Since these items require special tools, data and technical skills, have a Yamaha dealer per- form the service.

  • Page 20: Periodic Maintenance

    PERIODIC MAINTENANCE PERIODIC MAINTENANCE SPARK PLUG WARNING Check and adjust the areas around the cyl- inder head after the engine has cooled down completely. 1. Remove: 9 Spark plug cap 9 Spark plug NOTICE Before removing the spark plug, use com- pressed air to clean the cylinder head cover to prevent dirt from falling into the engine.
  • Page 21 PERIODIC MAINTENANCE Feeler gauge set: YU-26900-9 Thickness gauge: 90890-03180 Spark plug gap: Refer to “SPECIFICATIONS” in the Supplementary service manual. Before installing the spark plug, clean the gas- ket surface and plug surface. 4. Install: 9 Spark plug Spark plug: Refer to “TIGHTENING TORQUES”...

  • Page 22: Fuel Leakage

    PERIODIC MAINTENANCE FUEL LEAKAGE 1. Check: 9 Leakage Check at fuel tank, fuel cock, fuel hose, and carburetor. NOTICE Replace fuel hose every four years. ENGINE OIL LEAKAGE 1. Place the multi-purpose engine on a level surface. 2. Check the areas outside of the engine for oil leakage.

  • Page 23: Replacing The Engine Oil

    PERIODIC MAINTENANCE REPLACING THE ENGINE OIL 1. Warm up the engine for several minutes, and then stop the engine. 2. Remove: 9 Oil filler cap 1 9 Oil drain bolt 2 9 Oil drain bolt gasket 3 9 This engine is equipped with two oil filler caps.

  • Page 24: Air Filter Element

    PERIODIC MAINTENANCE AIR FILTER ELEMENT NOTICE Be sure not to run the engine without air filter element. Otherwise this can result in excessive piston and/or cylinder wear. 1. Remove: 9 Air filter cover screws 1 9 Air filter cover 2 2.

  • Page 25: Muffler

    PERIODIC MAINTENANCE MUFFLER WARNING The engine and muffler will be very hot after the engine has been run. Avoid touching the engine and muffler while they are still hot with any part of your body or clothing during check or repair.

  • Page 26: Fuel Tank Filter

    PERIODIC MAINTENANCE 5. Decarbonize: 9 Spark arrester NOTICE When cleaning with a wire brush, use it softly to avoid damage or scratch the spark arrester. 6. Install: 9 Muffler (Refer to “MUFFLER” on 3-7) 9 Spark arrester 9 Spark arrester screw Spark arrester screw: Refer to “TIGHTENING TORQUES”...

  • Page 27: Fuel Cock Strainer

    PERIODIC MAINTENANCE 3. Install: 9 Fuel tank filter 9 Fuel tank cap WARNING Make sure that the tank cap is tightened securely. FUEL COCK STRAINER WARNING Do not smoke, and keep away from open flames, sparks, or any other source of fire when handling or in the vicinity of fuel.

  • Page 28: Breather Hose

    PERIODIC MAINTENANCE 4. Install: 9 Fuel cock strainer 9 Gasket 9 Strainer cup Strainer cup: Refer to “TIGHTENING TORQUES” in the Supplementary service manual. WARNING Make sure that the strainer cup is tight- ened securely. BREATHER HOSE 1. Check: 9 Breather hose 1 Crack/damage →...

  • Page 29: Adjusting The Valve Clearance

    PERIODIC MAINTENANCE ADJUSTING THE VALVE CLEARANCE 1. Remove: 9 Spark plug cap 1 9 Spark plug 2 NOTICE Before removing the spark plug, use com- pressed air to clean the cylinder head cover to prevent dirt from falling into the engine.
  • Page 30 PERIODIC MAINTENANCE Valve clearance (cold): Refer to “SPECIFICATIONS” in the Supplementary service manual. 5. Adjust: 9 Valve clearance Adjustment steps: a. Loosen the locknut 1 and insert the 0.07 mm (0.0028 in) thickness gauge between the rocker arm and the valve tip.

  • Page 31: Engine Speed (With Throttle Lever Model)

    PERIODIC MAINTENANCE 6. Install: 9 Cylinder head cover gasket 9 Cylinder head cover Cylinder head cover bolt: Refer to “TIGHTENING TORQUES” in the Supplementary service manual. 9 Breather hose 9 Spark plug Spark plug: Refer to “TIGHTENING TORQUES” in the Supplementary service manual.

  • Page 32: Engine Speed

    PERIODIC MAINTENANCE 4. Measure: 9 Low engine speed (with no load). Out of specification → Adjust Low engine speed: Refer to “SPECIFICATIONS” in the Supplementary service manual. Measurement steps: a. Move the throttle lever 1 to the low engine speed position a. b.
  • Page 33 PERIODIC MAINTENANCE 3. Adjust: 9 Engine speed Adjustment steps: a. Loosen the throttle stop screw 1. b. Move the throttle lever 2 to direction a or b unit the high engine speed is obtained. High engine speed: Refer to “SPECIFICATIONS” in the Supplementary service manual.

  • Page 34: Recoil Starter

    PERIODIC MAINTENANCE ADJUSTING THE ENGINE SPEED 1. Warm up the engine for a few minutes. 2. Attach: 9 Digital tachometer 1 Digital tachometer: YU-39951-B, 90890-06760 3. Adjust: 9 Engine speed Adjustment steps: a. Turn the throttle stop screw 1 in direc- tion a or b until the engine speed is obtained.

  • Page 35: Chapter 3. Engine

    ENGINE INSPECTION ENGINE ENGINE INSPECTION MEASURING THE COMPRESSION PRESSURE Measure the compression pressure after checking and adjusting the valve clearance. 1. Warm up the engine for a few minutes. 2. Remove: 9 Spark plug cap 9 Spark plug NOTICE Before removing the spark plug, use com- pressed air to clean the cylinder head cover to prevent dirt from falling into the engine.
  • Page 36 ENGINE INSPECTION 4. Measure: 9 Compression pressure Crank the engine until the needle stop rising on the compression gauge. Out of specification → Refer to the testing steps. Standard compression pressure: Refer to “SPECIFICATIONS” in the Supplementary service manual. WARNING To prevent sparking when cranking the engine, ground the high tension cord.

  • Page 37: Air Filter

    AIR FILTER AIR FILTER SILENT SEMI-DRY TYPE 9 Nm (0.9 m · kgf, 6.5 ft · lbf) 1.6 Nm (0.16 m · kgf, 1.2 ft · lbf) 10 Nm (1.0 m · kgf, 7.2 ft · lbf) 1.6 Nm (0.16 m · kgf, 1.2 ft · lbf) Order Job/Parts to remove Q’ty...

  • Page 38: Semi-Cyclone Type

    AIR FILTER SEMI-CYCLONE TYPE 9 Nm (0.9 m · kgf, 6.5 ft · lbf) Order Job/Parts to remove Q’ty Remarks Removing the air filter Remove the parts in the order listed. Air filter cover Air filter element Breather hose Air filter case Gasket For installation, reverse the removal pro- cedure.

  • Page 39: Fuel Tank, Canister

    FUEL TANK, CANISTER FUEL TANK, CANISTER 10 Nm (1.0 m · kgf, 7.2 ft · lbf) 10 Nm (1.0 m · kgf, 7.2 ft · lbf) 29 Nm (2.9 m · kgf, 21 ft · lbf) 0.8 Nm (0.08 m · kgf, 0.6 ft · lbf) 6 Nm (0.6 m ·...

  • Page 40: Checking The Canister

    FUEL TANK, CANISTER CHECKING THE CANISTER 1. Check: 9 Canister 1 Cracks/damage → Replace.

  • Page 41: Muffler

    MUFFLER MUFFLER 10 Nm (1.0 m · kgf, 7.2 ft · lbf) 10 Nm (1.0 m · kgf, 7.2 ft · lbf) 1.8 Nm (0.18 m · kgf, 1.3 ft · lbf) 20 Nm (2.0 m · kgf, 14 ft · lbf) 20 Nm (2.0 m ·...

  • Page 42: Installing The Muffler

    MUFFLER INSTALLING THE MUFFLER 1. Install: 9 Gasket 9 Muffler assembly 9 Muffler nut 1 9 Muffler nut 2 9 Muffler bolt 3 Temporarily tighten the nut 1, nut 2, and bolt 3 until just comes in contact with the surface. 2.

  • Page 43: Recoil Starter

    RECOIL STARTER RECOIL STARTER 5.4 Nm (0.54 m · kgf, 3.9 ft · lbf) 7 Nm (0.7 m · kgf, 5.1 ft · lbf) 7 Nm (0.7 m · kgf, 5.1 ft · lbf) Order Job/Parts to remove Q’ty Remarks Removing the recoil starter Remove the parts in the order listed.

  • Page 44: Disassembling The Recoil Starter

    RECOIL STARTER DISASSEMBLING THE RECOIL STARTER 1. Remove: 9 Starter handle 1 Before untying the knot a above the starter handle, make a knot b on the rope so that the rope is not pulled into the case. 2. Remove: 9 Drive plate screw 1 9 Drive plate/Clip 9 Drive pawls...

  • Page 45: Checking The Recoil Starter

    RECOIL STARTER CHECKING THE RECOIL STARTER 1. Check: 9 Starter rope Wear/damage → Replace. 9 Starter case Cracks/damage → Replace. 9 Starter spring Dirt → Clean and apply grease. Wear/damage → Replace. 2. Check: 9 Drive pawls 1 9 Drive plate 2 Wear/damage →...
  • Page 46 RECOIL STARTER 4. Install: 9 Drive plate/Clip 1 5. Install: 9 Starter handle 9 Drive plate screw 1 To set the spring preload, hook the starter rope into the sheave drum slot a and turn the sheave drum assembly counterclockwise four times, and then unhook the starter rope from the slot.

  • Page 47: Flywheel

    FLYWHEEL FLYWHEEL 10 Nm (1.0 m · kgf, 7.2 ft · lbf) 7 Nm (0.7 m · kgf, 5.1 ft · lbf) 120 Nm (12 m · kgf, 87 ft · lbf) 7 Nm (0.7 m · kgf, 5.1 ft · lbf) 7 Nm (0.7 m ·...

  • Page 48: Removing The Flywheel

    FLYWHEEL REMOVING THE FLYWHEEL 1. Remove: 9 Flywheel cover 9 TCI unit 2. Remove: 9 Flywheel nut 1 9 Washer 9 Starter pulley Attach the sheave holder 2 to hold the fly- wheel. Primary clutch holder: YS-01880-A Sheave holder: 90890-01701 3.

  • Page 49: Installing The Flywheel

    FLYWHEEL INSTALLING THE FLYWHEEL 1. Install: 9 Woodruff key 9 Flywheel 2. Install: 9 Starter pulley 9 Washer 9 Flywheel nut 1 Flywheel nut: Refer to “TIGHTENING TORQUES” in the Supplementary service manual. Tighten the flywheel nut 1 using the sheave holder 2 to hold the flywheel.

  • Page 50: Installing The Tci Unit

    FLYWHEEL INSTALLING THE TCI UNIT 1. Install: 9 TCI unit 9 TCI unit bolts TCI unit bolt: Refer to “TIGHTENING TORQUES” in the Supplementary service manual. 2. Measure: 9 TCI unit air gap Out of specification → Adjust. Feeler gauge set: YU-26900-9 Thickness gauge: 90890-03180...

  • Page 51: Governor

    GOVERNOR GOVERNOR Order Job/Parts to remove Q’ty Remarks Removing the governor Remove the parts in the order listed. Fuel tank Refer to “FUEL TANK, CANISTER” on 3-5. Fuel tank stay Refer to “FUEL TANK, CANISTER” on 3-5. Engine switch and oil warning unit Refer to “ENGINE SWITCH AND OIL WARNING UNIT”...

  • Page 52: Checking The Flyweight Shaft Assembly And Governor Shaft

    GOVERNOR REMOVING THE FLYWEIGHT SHAFT ASSEMBLY AND GOVERNOR SHAFT 1. Remove: 9 Crankcase cover (Refer to “PISTON, CAMSHAFT, CRANKCASE, AND CRANKSHAFT” on 3-32) 9 Governor arm 2. Remove: 9 Clip 1 9 Governor shaft 2 9 Washers 3 3. Remove: 9 Flyweight shaft assembly 1 9 Washer 2 Remove the flyweight shaft assembly by tap-...

  • Page 53: Assembling The Flyweight Shaft Assembly

    GOVERNOR 2. Check: 9 Flyweight gear 9 Flyweight shaft 9 Collar 9 Washer 9 Governor shaft Wear/damage → Replace. ASSEMBLING THE FLYWEIGHT SHAFT ASSEMBLY 1. Install: 9 Flyweight shaft 1 9 Circlip 2 9 Washer 3 9 Collar 4 9 Weights 5 9 Weight shafts 6 INSTALLING THE FLYWEIGHT SHAFT ASSEMBLY AND GOVERNOR SHAFT...

  • Page 54: Engine Switch And Oil Warning Unit

    ENGINE SWITCH AND OIL WARNING UNIT ENGINE SWITCH AND OIL WARNING UNIT 0.7 Nm (0.07 m · kgf, 0.5 ft · lbf) 4.5 Nm (0.45 m · kgf, 3.3 ft · lbf) 4.5 Nm (0.45 m · kgf, 3.3 ft · lbf) Order Job/Parts to remove Q’ty...

  • Page 55: Cylinder Head Cover, Cylinder Head

    CYLINDER HEAD COVER, CYLINDER HEAD CYLINDER HEAD COVER, CYLINDER HEAD 11 Nm (1.1m · kgf, 8.0 ft · lbf) 20 Nm (2.0 m · kgf, 14 ft · lbf) 11 Nm (1.1m · kgf, 8.0 ft · lbf) 2.3 Nm (0.23m · kgf, 1.7 ft · lbf) 12 Nm (1.2 m ·...
  • Page 56 CYLINDER HEAD COVER, CYLINDER HEAD 11 Nm (1.1m · kgf, 8.0 ft · lbf) 20 Nm (2.0 m · kgf, 14 ft · lbf) 11 Nm (1.1m · kgf, 8.0 ft · lbf) 2.3 Nm (0.23m · kgf, 1.7 ft · lbf) 12 Nm (1.2 m ·...

  • Page 57: Checking The Rocker Arm

    CYLINDER HEAD COVER, CYLINDER HEAD CHECKING THE ROCKER ARM 1. Check: 9 Rocker arm Wear/damage/cracks → Replace. CHECKING THE PUSH ROD 1. Check: 9 Push rod runout Runout limit: Refer to “SPECIFICATIONS” in the Supplementary service manual. Out of specifications → Replace. CHECKING THE CYLINDER HEAD 1.

  • Page 58: Installing The Cylinder Head Assembly

    CYLINDER HEAD COVER, CYLINDER HEAD 3. Measure: 9 Cylinder head warpage Measure the warpage on the contact surface of the cylinder head at six points using the straight edge and thickness gauge. Warpage limit: Refer to “SPECIFICATIONS” in the Supplementary service manual.

  • Page 59: Valve

    VALVE VALVE Order Job/Parts to remove Q’ty Remarks Removing the valve Remove the parts in the order listed. Cylinder head Refer to “CYLINDER HEAD COVER, CYLINDER HEAD” on 3-21. Valve cotter Valve spring retainer Valve spring Exhaust valve Intake valve Valve stem seal Intake side only.

  • Page 60: Removing The Valve And Valve Spring

    VALVE REMOVING THE VALVE AND VALVE SPRING 1. Remove: 9 Valve cotters 1 9 Valve spring retainers 2 9 Valve springs 3 9 Valves 4 9 Valve stem seal (Intake side only) Remove the parts using the valve spring compressor 5. Do not compress the spring more than neces- sary.
  • Page 61 VALVE 2. Measure: 9 Valve stem diameter a Valve stem diameter: Refer to “SPECIFICATIONS” in the Supplementary service manual. Limit: Refer to “SPECIFICATIONS” in 302-001 the Supplementary service manual. Out of specifications → Replace. 3. Measure: 9 Valve stem runout Valve stem runout limit: Refer to “SPECIFICATIONS”...

  • Page 62: Checking The Valve Seat

    VALVE 5. Measure: 9 Compressed valve spring force a Out of specification → Replace the valve spring. Installed compression spring force: Refer to “SPECIFICATIONS” in the Supplementary service manual. Installed length: Refer to “SPECIFICATIONS” in the Supplementary service manual. b Installed length 6.
  • Page 63 VALVE Do not rotate the valve while the valve face is contacting the valve seat. 4. Measure: 9 Valve face contact width b Make sure that the contact width along the entire valve face is within specifica- tions. Valve face contact width: Refer to “SPECIFICATIONS”...

  • Page 64: Valve Lapping

    VALVE 6. Remove carbon deposits on the valve face a and valve seat. 9 Valve face contact seat width b 9 Valve margin thickness c Apply a small amount of coarse mechanic’s blueing dye (Dykem) to the valve seat. Press the valve through the valve guide and onto the valve seat to make a clear impression.

  • Page 65: Installing The Valve And Valve Spring

    VALVE NOTICE Do not let the lapping compound enter the gap between the valve stem and the valve guide. After every lapping procedure, clean off the compound from the valve face and valve seat. INSTALLING THE VALVE AND VALVE SPRING 1.

  • Page 66: Piston, Camshaft, Crankcase, And Crankshaft

    PISTON, CAMSHAFT, CRANKCASE, AND CRANKSHAFT PISTON, CAMSHAFT, CRANKCASE, AND CRANKSHAFT 27 Nm (2.7 m · kgf, 20 ft · lbf) 27 Nm (2.7 m · kgf, 20 ft · lbf) 10 Nm (1.0 m · kgf, 7.2 ft · lbf) 10 Nm (1.0 m ·...
  • Page 67 PISTON, CAMSHAFT, CRANKCASE, AND CRANKSHAFT 20 Nm (2.0 m · kgf, 14 ft · lbf) Order Job/Parts to remove Q’ty Remarks Camshaft Valve lifter Crankshaft shim — P.T.O. shaft type E Connecting rod cap Crankshaft Connecting rod Piston pin circlip Piston pin Piston Piston ring set...

  • Page 68: Removing The Camshaft And Valve Lifter

    PISTON, CAMSHAFT, CRANKCASE, AND CRANKSHAFT REMOVING THE CAMSHAFT AND VALVE LIFTER 1. Remove: 9 Camshaft 1 Remove the camshaft when the camshaft gear mark a and the crankshaft gear mark b are aligned. 2. Remove: 9 Intake valve lifter 1 9 Exhaust valve lifter 2 NOTICE Mark the intake and exhaust valve lifters...
  • Page 69 PISTON, CAMSHAFT, CRANKCASE, AND CRANKSHAFT 2. Check: 9 Camshaft lobe dimensions a and b Camshaft lobe dimensions: Dimension a: Refer to “SPECIFICATIONS” in the Supplementary service manual. Limit: Refer to “SPECIFICATIONS” in the Supplementary service manual. Dimension b: Refer to “SPECIFICATIONS” in the Supplementary service manual.

  • Page 70: Checking The Valve Lifter

    PISTON, CAMSHAFT, CRANKCASE, AND CRANKSHAFT CHECKING THE VALVE LIFTER 1. Check: 9 Valve lifter Damage → Replace. INSTALLING THE VALVE LIFTER AND CAMSHAFT 1. Install: 9 Intake valve lifter 1 9 Exhaust valve lifter 2 2. Install: 9 Camshaft 1 NOTICE Be sure to align the camshaft gear mark a with the crankshaft gear mark b.

  • Page 71: Installing The Crankcase Cover

    PISTON, CAMSHAFT, CRANKCASE, AND CRANKSHAFT INSTALLING THE CRANKCASE COVER 1. Install: 9 Crankcase cover 9 Crankcase cover bolts 1 to 8 Tighten the bolts to the specified torque in two stages and in order from 1 to 8. Crankcase cover bolt: Refer to “TIGHTENING TORQUES”...

  • Page 72: Checking The Crankcase

    PISTON, CAMSHAFT, CRANKCASE, AND CRANKSHAFT 2. Measure: 9 Cylinder warpage Measure the warpage on the contact surface of the cylinder head at six points using a straight edge and thickness gauge. Feeler gauge set: YU-26900-9 Thickness gauge: 90890-03180 Warpage limit: Refer to “SPECIFICATIONS”...

  • Page 73: Checking The Piston And Piston Pin

    PISTON, CAMSHAFT, CRANKCASE, AND CRANKSHAFT CHECKING THE PISTON AND PISTON PIN 1. Measure: 9 Piston skirt diameter P a = 10 mm (0.4 in) from the piston bottom edge Out of specification → Replace. Piston skirt diameter: Refer to “SPECIFICATIONS” in 307-001 the Supplementary service manual.
  • Page 74 PISTON, CAMSHAFT, CRANKCASE, AND CRANKSHAFT 3. Measure: 9 Piston pin hole inside diameter a Out of specifications → Replace. Piston pin hole inside diameter: Refer to “SPECIFICATIONS” in the Supplementary service manual. Limit: Refer to “SPECIFICATIONS” in the Supplementary service manual.

  • Page 75: Checking The Piston Ring

    PISTON, CAMSHAFT, CRANKCASE, AND CRANKSHAFT 5. Check: 9 Check that the piston pin enters smoothly into the piston pin hole. If the piston pin fits too tight into the piston, check the piston pin hole. If there is any pro- trusion, use a knife or scraper to gently remove it so that piston pin can be pushed in smoothly with your fingers.

  • Page 76: Checking The Crankshaft

    PISTON, CAMSHAFT, CRANKCASE, AND CRANKSHAFT 2. Measure: 9 Piston ring side clearance Out of specification → Replace the pis- ton and piston ring as a set. Use a thickness gauge 1. 9 Clean carbon deposits from the piston ring grooves and rings before measuring the side clearance.
  • Page 77 PISTON, CAMSHAFT, CRANKCASE, AND CRANKSHAFT 2. Measure: 9 Crankshaft runout limit Out of specification → Replace. Use a dial gauge. Dial indicator gauge: YU-A8428 Dial gauge: 90890-03097 Runout limit: Refer to “SPECIFICATIONS” in the Supplementary service manual. 3. Measure: 9 Crank pin outside diameter a Out of specification →...

  • Page 78: Checking The Connecting Rod Oil Clearance

    PISTON, CAMSHAFT, CRANKCASE, AND CRANKSHAFT CHECKING THE CONNECTING ROD OIL CLEARANCE Measure the oil clearance if replacing the crankshaft or connecting rod. 1. Place a piece of Plastigauge 1 on the ® crank pin horizontally. Wipe off oil thoroughly from the crankshaft, connecting rod, and connecting rod cap.

  • Page 79: Installing The Piston And Piston Ring

    PISTON, CAMSHAFT, CRANKCASE, AND CRANKSHAFT 3. Remove: 9 Connecting rod cap 9 Connecting rod 4. Measure: 9 Connecting rod big end oil clearance Out of specification → Replace crank- shaft or connecting rod assembly, and then measure the clearance again. Measure the widest portion of the pressed Plastigauge ®...

  • Page 80: Installing The Crankshaft

    3. Install: 9 Piston 1 9 Piston pin 2 9 Piston pin circlips 3 9 Make sure that the “YAMAHA” mark a on the connecting rod faces toward the crank- case cover. 9 Make sure that the “ ” mark b on the pis- ton head faces toward the push rod.
  • Page 81 9 Make sure that the “ ” mark a on the pis- ton head faces toward the push rod. 9 Make sure that the “YAMAHA” mark b on the connecting rod faces toward the crank- case cover. 5. Install:...

  • Page 82: Selecting The Crankshaft Shim (P.t.o. Shaft Type E)

    PISTON, CAMSHAFT, CRANKCASE, AND CRANKSHAFT 6. Install: 9 Connecting rod cap 1 9 Connecting rod cap bolts 2 Connecting rod cap bolt: Refer to “TIGHTENING TORQUES” in the Supplementary service manual. 9 Make sure that the “ ” mark a on the con- necting rod is aligned with the “...
  • Page 83 PISTON, CAMSHAFT, CRANKCASE, AND CRANKSHAFT 3. Adjust: 9 Crankshaft free play Adjustment steps: a. Remove the crankcase cover 1. (Refer to “PISTON, CAMSHAFT, CRANKCASE, AND CRANKSHAFT” on 3-32) b. Install or remove the shim 2 of the proper thickness. c. Install the crankcase cover 1. ( R e f e r t o “...

  • Page 84: Chapter 4. Carburetor

    CARB REMOVING THE CARBURETOR CARBURETOR REMOVING THE CARBURETOR å Order Job/Parts to remove Q’ty Remarks Removing the carburetor Remove the parts in the order listed. Fuel tank Refer to “FUEL TANK, CANISTER” on 3-5. Air filter Refer to “AIR FILTER” on 3-3. Choke solenoid lead Auto choke model Link rod/Spring...

  • Page 85: Disassembling The Carburetor

    CARB DISASSEMBLING THE CARBURETOR DISASSEMBLING THE CARBURETOR MANUAL CHOKE MODEL 3.5 Nm (0.35 m · kgf, 2.5 ft · lbf) 2.0 Nm (0.20 m · kgf, 1.4 ft · lbf) 3.5 Nm (0.35 m · kgf, 2.5 ft · lbf) 0.7 Nm (0.07 m ·...

  • Page 86: Auto Choke Model

    CARB DISASSEMBLING THE CARBURETOR AUTO CHOKE MODEL 3.5 Nm (0.35 m · kgf, 2.5 ft · lbf) 1.3 Nm (0.13 m · kgf, 0.94 ft · lbf) 2.0 Nm (0.20 m · kgf, 1.4 ft · lbf) 0.7 Nm (0.07 m · kgf, 0.52 ft · lbf) 3.5 Nm (0.35 m ·...
  • Page 87 CARB DISASSEMBLING THE CARBURETOR 3.5 Nm (0.35 m · kgf, 2.5 ft · lbf) 1.3 Nm (0.13 m · kgf, 0.94 ft · lbf) 2.0 Nm (0.20 m · kgf, 1.4 ft · lbf) 0.7 Nm (0.07 m · kgf, 0.52 ft · lbf) 3.5 Nm (0.35 m ·...

  • Page 88: Checking The Carburetor

    CARB DISASSEMBLING THE CARBURETOR CHECKING THE CARBURETOR 1. Measure: 9 Float height a Out of specification → Replace. 9 Lift up the float so that the tip of the float valve lightly contacts the float arm, and then measure the float height a. 9 Do not adjust the float height.

  • Page 89: Checking The Choke Solenoid (Auto Choke Model)

    CARB DISASSEMBLING THE CARBURETOR CHECKING THE CHOKE SOLENOID (AUTO CHOKE MODEL) 1. Check: Ω×1  9 Choke solenoid Connect the pocket tester (Ω×1). Measure the choke solenoid resist- ance. Choke solenoid resistance: Refer to “SPECIFICATIONS” in the Supplementary service manual. Analog pocket tester: YU-03112-C Pocket tester: 90890-03112...

  • Page 90: Chapter 5. Electrical

    ELEC ELECTRICAL COMPONENTS ELECTRICAL ELECTRICAL COMPONENTS 1 Spark plug 2 TCI unit 3 Charging coil (With charging coil model) 4 Oil warning unit 5 Engine switch 6 Oil level switch 7 Oil warning light...

  • Page 91: Fuse (Electric Starting Model)

    ELEC FUSE (ELECTRIC STARTING MODEL) FUSE (ELECTRIC STARTING MODEL) CHECKING THE FUSE NOTICE To avoid a short circuit, always set the engine switch to “STOP” when checking or replacing a fuse. 1. Remove: 9 Fuse 1 2. Check: 9 Fuse Checking steps: a. Connect the pocket tester (Ω × 1) to the fuse and check the continuity.
  • Page 92 ELEC FUSE (ELECTRIC STARTING MODEL) 3. Replace: 9 Blown fuse Replacing steps: a. Set the engine switch to “OFF”. b. Install a new fuse of the correct amper- age. c. Set the engine switch to “ON” and veri- fy if the electrical circuit is operational. d. If the fuse immediately blows again, check the electrical circuit. Fuse amperage: Refer to “SPECIFICATIONS” in the Supplementary service manual. WARNING Never use a fuse with an amperage other than that specified.

  • Page 93: Switches

    ELEC SWITCHES SWITCHES CHECKING THE SWITCH CONTINUITY Use a tester to check the terminals for conti- nuity. If a continuity error is found at any point, replace the switch. Analog pocket tester: YU-03112-C Pocket tester: 90890-03112 9 Set the pocket tester to “0” before starting a test. 9 To test the switch for continuity, set the pocket tester to the “Ω × 1” range. 9 Turn the switch on and off several times during the test.

  • Page 94: Ignition System

    ELEC IGNITION SYSTEM IGNITION SYSTEM TROUBLESHOOTING CHART NO SPARK OR WEAK SPARK Use the following special tool(s) for troubleshooting. Analog pocket tester: Oppama pet-4000 spark checker: YU-03112-C YM-34487 Pocket tester: Ignition checker: 90890-03112 90890-06754 1. Engine oil level 9 Check the oil level. (Refer to “ENGINE OIL LEVEL” on 2-5) OUT OF MEETS SPECIFICATION SPECIFICATION Add engine oil. 2. Spark plug 9 Check the spark plug condition. (Refer to “SPARK PLUG” on 2-3) NOT GOOD GOOD Repair or replace the spark plug.
  • Page 95 ELEC IGNITION SYSTEM 3. Ignition spark gap 9 Disconnect the spark plug cap 1 from the spark plug. 9 Connect the ignition checker 2 as shown. Spark plug cap 1 → Ignition checker 2 Ignition checker lead → Spark plug 3 9 Turn the crankshaft and measure the ignition spark gap a.
  • Page 96 ELEC IGNITION SYSTEM 4. Spark plug cap resistance 9 Do not pull out the spark plug cap from the 9 Remove the spark plug cap from the high tension cord. high tension cord. 9 Remove → Turn the spark plug cap coun- 9 Connect the pocket tester (Ω × 1k) to the terclockwise. spark plug cap. 9 Install → Turn the spark plug cap clockwise. 9 Check the high tension cord for cracks or deterioration before installing the spark plug Ω × 1k cap.
  • Page 97 ELEC IGNITION SYSTEM 6. Ignition coil (TCI unit) resistance 9 Remove the ignition coil (TCI unit). 9 Connect the pocket tester (Ω × 1) to the primary terminal. Tester + lead → Black/White terminal 1 Tester - lead → Body ground 2 Primary coil resistance: Refer to “SPECIFICATIONS” in the Supplementary service manual. OUT OF MEETS SPECIFICATION SPECIFICATION Replace the TCI unit. 7. Ignition coil (TCI unit) resistance 9 Remove the ignition coil (TCI unit). 9 Connect the pocket tester (Ω × 1k) to the secondary terminal.
  • Page 98 ELEC IGNITION SYSTEM 8. Engine switch 9 Disconnect the engine switch connec- tors. 9 Connect the pocket tester (Ω × 1) to the engine switch connectors. 9 Check the engine switch continuity. Tester + lead → Black terminal 1 Tester - lead → Black terminal 2 Switch “ON” a → No continuity Switch “OFF” b → Continuity OUT OF MEETS SPECIFICATION SPECIFICATION Replace the engine switch.
  • Page 99 ELEC IGNITION SYSTEM 9. Oil level switch 9 Remove the oil level switch from the bot- tom of the crankcase cover. ( R e fe r t o “ P I S TO N , C A M S H A F T, CRANKCASE, AND CRANKSHAFT” on 3-32) 9 Connect the pocket tester (Ω × 1) to the oil level switch lead and check for conti- nuity. Tester + lead → Oil level switch lead 1 Tester - lead →...

  • Page 100: Electric Starting System (Electric Starting Model)

    ELECTRIC STARTING SYSTEM ELEC (ELECTRIC STARTING MODEL) ELECTRIC STARTING SYSTEM (ELECTRIC STARTING MODEL) TROUBLESHOOTING CHART THE STARTER MOTOR DOES NOT OPERATE Use the following special tool(s) for troubleshooting. Analog pocket tester: Digital tachometer: YU-03112-C YU-39951-B, 90890-06760 Pocket tester: 90890-03112 1. Fuse 9 Remove the fuse. 9 Connect the pocket tester (Ω × 1) to the fuse. 9 Check the fuse for continuity. (Refer to “FUSE (ELECTRIC STARTING MODEL)” on 5-2) NO CONTINUITY CONTINUITY...
  • Page 101 ELECTRIC STARTING SYSTEM ELEC (ELECTRIC STARTING MODEL) 3. Starter motor 9 Connect the jumper lead to the starter relay terminals on the battery side and the starter motor side. 1 Jumper lead 9 Check the starter motor operation. DOES NOT MOVE Check the battery. MOVES NOT GOOD GOOD 4. Starter relay 9 Disconnect the engine switch coupler. Repair and/or charge the battery. 9 Connect the jumper lead to the starter relay coupler.

  • Page 102: Removing The Starter Motor

    ELECTRIC STARTING SYSTEM ELEC (ELECTRIC STARTING MODEL) REMOVING THE STARTER MOTOR 16 Nm (1.6 m · kgf, 12 ft · lbf) 16 Nm (1.6 m · kgf, 12 ft · lbf) Order Job/Parts to remove Q’ty Remarks Removing the starter motor Remove the parts in the order listed. Starter motor assembly For installation, reverse the removal pro- cedure.

  • Page 103: Disassembling The Starter Motor

    ELECTRIC STARTING SYSTEM ELEC (ELECTRIC STARTING MODEL) DISASSEMBLING THE STARTER MOTOR 8 Nm (0.8 m · kgf, 5.8 ft · lbf) 5 Nm (0.5 m · kgf, 3.6 ft · lbf) Order Job/Parts to remove Q’ty Remarks Disassembling the starter motor Disassemble the parts in the order listed. Rear bracket Plate Brush holder...

  • Page 104: Checking The Armature Coil

    ELECTRIC STARTING SYSTEM ELEC (ELECTRIC STARTING MODEL) CHECKING THE ARMATURE COIL 1. Check: 9 Commutator (outer surface) Dirty → Clean it with #600 grit sandpa- per. 2. Measure: 9 Mica (insulation depth between the commutator segments) Out of specification → Scrape the mica to the proper measurement using a hacksaw blade which has been ground- ed to fit the commutator. Depth of insulator a: Refer to “SPECIFICATIONS” in the Supplementary service manual.

  • Page 105: Checking The Brush

    ELECTRIC STARTING SYSTEM ELEC (ELECTRIC STARTING MODEL) 1 Continuity check 2 Insulation check 3 Armature coil CHECKING THE BRUSH 1. Measure: 9 Brush length (of each brush) 1 Out of specification → Replace. Limit: Refer to “SPECIFICATIONS” in the Supplementary service manual. 2. Check: 9 Brush spring 2 Fatigue/damage → Replace. Assembly 1. Reverse the disassembly steps. (Refer to “DISASSEMBLING THE STARTER MOTOR” on 5-14) CHECKING THE MAGNETIC SWITCH...
  • Page 106 ELECTRIC STARTING SYSTEM ELEC (ELECTRIC STARTING MODEL) Holding coil resistance: å – ∫ Refer to “SPECIFICATIONS” in the Supplementary service manual. Pull-in coil resistance: å – ç Refer to “SPECIFICATIONS” in the Supplementary service manual. 5-17...

  • Page 107: Charging System (With Charging Coil Model)

    ELEC CHARGING SYSTEM (WITH CHARGING COIL MODEL) CHARGING SYSTEM (WITH CHARGING COIL MODEL) TROUBLESHOOTING CHART THE CHARGING COIL IS NOT WORKING Use the following special tool(s) for troubleshooting. Analog pocket tester: YU-03112-C Pocket tester: 90890-03112 1. Charging coil resistance 9 Disconnect the charging coil leads. 9 Connect the pocket tester (Ω × 1). Measure the charging coil resistance. Charging coil resistance: Connector 1 –Ground 2 : Refer to “SPECIFICATIONS”...
  • Page 108 TRBL ENGINE TROUBLESHOOTING ENGINE ENGINE DOES NOT START Check that the oil warning light comes on by pull- ing the starter rope. LIGHTS ON DOSE NOT LIGHT Check the connections between the oil warning unit and oil level switch. GOOD NOT GOOD Replace the oil warning light, oil warning unit, or oil level switch.
  • Page 109 TRBL ENGINE Remove the spark plug and attach it to the spark plug cap, and then ground the spark plug to check for spark. GOOD SPARK WEAK OR NO SPARK 9 Check the spark plug for dirt and check the spark plug gap.
  • Page 110 TRBL ENGINE Check if the marks on the crankshaft and cam- shaft are aligned. ALIGNED NOT ALIGNED Correct. Check if there is seizure, wear, or damage on the piston, piston ring, or cylinder. Rebore or replace. GOOD SEIZURE OR WORN...
  • Page 111 TRBL ENGINE ENGINE STARTS BUT STALLS Check the fuel level. Add. SUFFICIENT INSUFFICIENT Check if the fuel tank cap is clogged. Clean or replace. GOOD CLOGGED Check if the fuel cock is clogged. GOOD CLOGGED Clean. Check if the fuel hose is clogged. GOOD CLOGGED Clean.
  • Page 112 TRBL ENGINE ENGINE SPEED DOES NOT INCREASE Check the spark plug for dirt and check the spark plug gap. Clean, adjust, or replace. DIRTY OR OUT OF GOOD SPECIFICATION Check the air filter element for dirt. Clean. GOOD DIRTY Check the compression pressure. Decarbonize the com- TOO HIGH bustion chamber if there...
  • Page 113 TRBL ENGINE ENGINE SPEED IS UNEVEN Check the fuel level. Add. SUFFICIENT INSUFFICIENT Check if fuel has deteriorated. Replace. GOOD DETERIORATED Check if the fuel tank cap is clogged. GOOD CLOGGED Replace. Check if the fuel cock is clogged. GOOD CLOGGED Clean.
  • Page 114 TRBL ENGINE Check the valve clearance. OUT OF Adjust. SUFFICIENT SPECIFICATION Check the valve face and valve seat for wear. GOOD WORN Resurface or replace. Check if there is seizure, wear, or damage on the piston, piston ring, or cylinder. GOOD SEIZURE OR WORN Rebore or replace.
  • Page 115 TRBL ENGINE GOVERNOR OPERATION Check that the governor link operate smoothly. Adjust or replace. GOOD NO GOOD Check that the governor spring is stretched. Replace. GOOD STRETCHED Check the governor adjustment. GOOD NOT GOOD Adjust. Check the governor weight and governor bushing function.
  • Page 116 TRBL...
  • Page 118 2012_09×1 !

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