Yamaha MX250 Service Manual Download Page 108

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7-8

SPECIFICA

IONS

TIGHTENING TORQUES

Item

Thread size

Tightening torque

Air filter cover nut



1.0

1.6 N·m (0.16 kgf·m, 1.2 lb·ft)

Air filter element nut



1.0

0.9 N·m (0.09 kgf·m, 0.66 lb·ft)

Duct bolt



1.0

7 N·m (0.7 kgf·m, 5.2 lb·ft)

Duct nut



1.25

9 N·m (0.9 kgf·m, 6.6 lb·ft)

Fuel tank bolt



1.0

10 N·m (1.0 kgf·m, 7.4 lb·ft)

Fuel tank stay bolt



1.25

29 N·m (2.9 kgf·m, 21 lb·ft)

Fuel cock

M10



1.25

6 N·m (0.6 kgf·m, 4.4 lb·ft)

Fuel cock screw

—

0.8 N·m (0.08 kgf·m, 0.59 lb·ft)

Strainer cup

—

1.3 N·m (0.13 kgf·m, 0.95 lb·ft)

Muffler bolt



1.25

20 N·m (2.0 kgf·m, 15 lb·ft)

Muffler nut



1.25

20 N·m (2.0 kgf·m, 15 lb·ft)

Muffler cover bolt



1.0

10 N·m (1.0 kgf·m, 7.4 lb·ft)

Spark arrester screw

—

1.8 N·m (0.18 kgf·m, 1.3 lb·ft)

Recoil starter bolt



1.0

7 N·m (0.7 kgf·m, 5.2 lb·ft)

Drive plate screw



1.0

5.4 N·m (0.54 kgf·m, 3.9 lb·ft)

Flywheel cover bolt



1.0

7 N·m (0.7 kgf·m, 5.2 lb·ft)

TCI unit bolt



1.0

10 N·m (1.0 kgf·m, 7.4 lb·ft)

Flywheel nut

M18



1.5

100 N·m (10 kgf·m, 74 lb·ft)

Governor arm bolt



1.0

8 N·m (0.8 kgf·m, 5.9 lb·ft)

Throttle lever assembly bolt



1.0

7 N·m (0.7 kgf·m, 5.2 lb·ft)

Throttle lever assembly plate
screw



0.8

1.1 N·m (0.11 kgf·m, 0.81 lb·ft)

Throttle lever assembly wire screw



0.7

1.1 N·m (0.11 kgf·m, 0.81 lb·ft)

Oil warning unit bolt



1.0

7 N·m (0.7 kgf·m, 5.2 lb·ft)

Engine switch screw



1.0

4.5 N·m (0.45 kgf·m, 3.3 lb·ft)

Spark plug

M14



1.25

20 N·m (2.0 kgf·m, 15 lb·ft)

Cylinder head cover bolt



1.0

11 N·m (1.1 kgf·m, 8.1 lb·ft)

Valve adjuster locknut



0.5

7 N·m (0.7 kgf·m, 5.2 lb·ft)

Rocker arm shaft screw



0.8

2.3 N·m (0.23 kgf·m, 1.7 lb·ft)

Cylinder head bolt

M10



1.25

1st: 12 N·m (1.2 kgf·m, 8.9 lb·ft)

2nd: 50 N·m (5.0 kgf·m, 37 lb·ft)

Exhaust stud bolt



1.25

11 N·m (1.1 kgf·m, 8.1 lb·ft)

Crankcase cover bolt



1.25

1st: 12 N·m (1.2 kgf·m, 8.9 lb·ft)

2nd: 30 N·m (3.0 kgf·m, 22 lb·ft)

Oil level switch bolt



1.0

10 N·m (1.0 kgf·m, 7.4 lb·ft)

Oil level switch clamp bolt



1.0

10 N·m (1.0 kgf·m, 7.4 lb·ft)

Oil drain bolt

M12



1.5

27 N·m (2.7 kgf·m, 20 lb·ft)

Connecting rod cap bolt



1.25

20 N·m (2.0 kgf·m, 15 lb·ft)

Float chamber bolt

—

7 N·m (0.7 kgf·m, 5.2 lb·ft)

Carburetor drain screw

—

1.3 N·m (0.13 kgf·m, 0.95 lb·ft)

Summary of Contents for MX250

Page 1: ...SERVICE MANUAL MX250 MX300 7VE F8197 10 LIT 19616 02 45 2017 03 1 7VE F8197 10_Cover indd 1 2017 03 16 16 24 49 ...

Page 2: ...7VE F8197 10_Cover indd 2 2017 03 16 16 24 50 ...

Page 3: ...UAL 2017 by Yamaha Motor Corporation U S A 1st Edition March 2017 All rights reserved Any reprinting or unauthorized use without the written permission of Yamaha Motor Corporation U S A is expressly prohibited LIT 19616 02 45 ...

Page 4: ...h the most satisfaction from his machine and to con form to federal environmental quality objectives Yamaha Motor Powered Products Co Ltd is continually striving to improve all of its models Modifi cations and significant changes in specifications or procedures will be forwarded to all authorized Yamaha dealers and will appear in future editions of this manual where applicable TIP This Service Man...

Page 5: ...uen tially 7 4 3 1 2 3 5 6 7 8 9 10 DISASSEMBLING THE CARBURETOR CHECKING THE CARBURETOR 1 Measure Float height a Out of specification Replace TIP Lift up the float so that the tip of the float valve lightly contacts the float arm and then measure the float height a Do not adjust the float height 2 Check Jets Carburetor body Clogged Apply compressed air to clean the jet 3 Check Valve seat Wear dam...

Page 6: ...ant to every machine SYMBOL DEFINITION SYMBOL DEFINITION 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 Silicone fluid Apply locking agent LOCTITE T R New LS M E S LT ...

Page 7: ...GENERAL INFORMATION PERIODIC CHECKS AND ADJUSTMENTS ENGINE CARBURETOR ELECTRICAL TROUBLESHOOTING SPECIFICATIONS 1 2 3 4 5 6 7 8 9 10 INDEX ...

Page 8: ...5 AIR FILTER ELEMENT 2 6 MUFFLER 2 7 FUEL TANK FILTER 2 9 FUEL COCK STRAINER 2 10 BREATHER HOSE 2 11 CYLINDER HEAD DECARBONIZATION 2 11 ADJUSTING THE VALVE CLEARANCE 2 11 ENGINE SPEED 2 13 ADJUSTING THE ENGINE SPEED 2 14 RECOIL STARTER 2 15 FITTINGS AND FASTENERS 2 16 ENGINE ENGINE INSPECTION 3 1 MEASURING THE COMPRESSION PRESSURE 3 1 AIR FILTER 3 3 FUEL TANK 3 4 CHECKING THE FUEL TANK CAP CANISTE...

Page 9: ... 37 CHECKING THE CRANKCASE 3 38 CHECKING THE PISTON PIN 3 39 CHECKING THE PISTON RINGS 3 39 CHECKING THE CRANKSHAFT 3 41 CHECKING THE CONNECTING ROD OIL CLEARANCE 3 41 INSTALLING THE PISTON AND PISTON RING 3 42 INSTALLING THE CRANKSHAFT 3 43 CARBURETOR REMOVING THE CARBURETOR 4 1 DISASSEMBLING THE CARBURETOR 4 2 CHECKING THE CARBURETOR 4 3 ELECTRICAL CIRCUIT DIAGRAM 5 1 ELECTRICAL COMPONENTS 5 3 C...

Page 10: ...RQUES 7 8 GENERAL TORQUE SPECIFICATIONS 7 10 LUBRICATION POINTS AND TYPE OF LUBRICANTS 7 11 WIRE ROUTING DIAGRAM 7 12 UPPER SIDE VIEW 7 12 ENGINE SWITCH AND OIL WARNING UNIT 7 14 TCI UNIT 7 16 OIL LEVEL SWITCH CRANKCASE COVER 7 18 ...

Page 11: ...osition of the multi purpose engine as shown in the illus tration TIP The first four digits identify the model and the remaining digits indicates the production number Designs and specifications are subject to change without notice STARTING SERIAL NUMBER MX300 296 7VE 7VE 1 Model Code Starting serial num ber 7KHJ 020 7KHJ 7KHJ 1000101 7VEJ 020 7VEJ 7VEJ 1000101 ...

Page 12: ...ad Unit in 2 UNC Unified coarse thread Unit in in mm 4 5 5 72 2 28 56 88 5 25 4 0 021 0 110 0 054 0 146 08 0 040 0 21 8 0 1 0 6 31 7 16 20UNF 2B 30 30 45 45 45 45 6 5 165 1 5 127 1 37 35 1 37 35 4 05 103 5 75 0 0 0016 4 33 0 0021 0 4 3 8 16UNC2B DEPTH0 71 4 5 16 24UNF 2B DEPTH0 71 2 5 16 24UNF 2B DEPTH0 71 ...

Page 13: ...1 3 1 2 3 4 5 6 7 8 9 10 GENERAL INFORMATION DIMENSIONS TOP MOUNTING BASE in mm in mm 17 49 444 5 4 13 105 3 56 90 5 2 0 43 11 0 63 16 0 43 11 2 2 32 59 1 46 37 ...

Page 14: ...DIMENSIONS 1 4 1 2 3 4 5 6 7 8 9 10 GENERAL INFORMATION LEFT SIDE in mm 4 06 103 2 76 70 18 85 479 ...

Page 15: ...1 5 1 2 3 4 5 6 7 8 9 10 GENERAL INFORMATION DIMENSIONS FRONT in mm 15 36 390 3 7 2 183 8 16 207 3 3 48 88 5 ...

Page 16: ...g the engine always keep the engine and yourself away from fire NOTES ON SERVICE Correct tools Be sure to use the correct special tool for the job to guard against damage Oil grease and seals Be sure to use genuine Yamaha oils grease and sealers or the equivalents Expendable parts Always replace the gaskets O rings cotter pins and cir clips with new parts when servicing engine ...

Page 17: ...sassembly Contact surfaces of moving parts should be oiled when reassembled Make sure that the parts move smoothly after each sec tion of the machine is assembled ALL REPLACEMENT PARTS We recommend the use of genuine Yamaha parts for all replacements 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 repla...

Page 18: ...ium base grease to the seal lip s Oil the bearings liberally when installing BASIC SERVICE INFORMATION ELECTRICAL SYSTEM Checking the electrical system TIP Before checking the electrical system make sure that the battery voltage is at least 12 V 1 2 Do not use compressed air to spin the bearings dry This causes damage to the bearing surfaces NOTICE a Never insert the tester probes into the coupler...

Page 19: ...r blower Rust stains Connect and disconnect several times When disconnecting a coupler release the coupler lock hold both sections of the coupler securely and then disconnect the coupler There are many types of coupler locks therefore be sure to check the type of coupler lock before discon necting the coupler NOTICE When disconnecting a connector do not pull the leads Hold both sections of the con...

Page 20: ... the terminal is flattened bend it up After disassembling and assembling a coupler pull on the leads to make sure that they are installed securely 4 Connect Lead Coupler Connector TIP When connecting a coupler or connector push both sec tions of the coupler or connector together until they are connected securely Make sure all connections are tight 1 ...

Page 21: ...r and coupler of the TCI unit CDI unit when replacing the TCI unit CDI unit As a quick remedy use a contact revitalizer available at most part stores Model 88 Multimeter with tachometer YU A1927 Digital circuit tester CD732 90890 03243 For waterproof couplers never insert the tester leads directly into the coupler When performing any checks using a waterproof coupler use the specified test har nes...

Page 22: ...732 90890 03243 Feeler gauge set YU 26900 9 Thickness gauge 90890 03180 Six piece tappet set YM A5970 Tappet adjusting tool 90890 01311 Digital tachometer YU 39951 B 90890 06760 Engine compression tes ter YU 33223 Compression gauge 90890 03081 Extension 90890 04082 Primary clutch holder YS 01880 A Sheave holder 90890 01701 Heavy duty puller YU 33270 B Flywheel puller 90890 01362 Valve spring compr...

Page 23: ...ction to ensure air filter but are also vital to proper engine operation and maximum performance PERIODIC MAINTENANCE LUBRICATION INTERVALS Item Routine Pre opera tion check Initial Every 1 month or 20 Hrs 3 months or 50 Hrs 6 months or 100 Hrs 12 months or 300 Hrs Spark plug Check condition Clean and replace if nec essary Fuel Check fuel level and leak age Fuel hose Check fuel hose for cracks or ...

Page 24: ...ms require special tools data and technical skills have a Yamaha dealer per form the service Idle speed Check and adjust idle speed Recoil starter Check recoil starter for damage Fittings fasten ers Check all fittings and fas teners Correct if necessary The point where abnormality was recognized by use Item Routine Pre opera tion check Initial Every 1 month or 20 Hrs 3 months or 50 Hrs 6 months or...

Page 25: ...f specification Regap If necessary clean the spark plug with a spark plug cleaner TIP Before installing the spark plug clean the gasket surface and plug surface Check and adjust the areas around the cylinder head after the engine has cooled down completely WARNING Before removing the spark plug use compressed air to clean the cylinder head cover to prevent dirt from falling into the engine NOTICE ...

Page 26: ...ge Check at fuel tank fuel cock fuel hose and carbu retor ENGINE OIL LEAKAGE 1 Place the multi purpose engine on a level surface 2 Check the areas outside of the engine for oil leakage Oil leakage Replace the gasket oil seal or O ring ENGINE OIL LEVEL 1 Remove Oil filler cap 1 TIP This engine is equipped with two oil filler caps Use which ever side is accessible a b Spark plug 20 N m 2 0 kgf m 15 ...

Page 27: ...d oil if necessary 3 Install Oil filler cap REPLACING THE ENGINE OIL 1 Warm up the engine for several minutes and then stop the engine 2 Remove Oil filler cap 1 Oil drain bolt 2 Oil drain bolt gasket 3 TIP This engine is equipped with two oil filler caps Use whichever side is accessible This engine is equipped with two oil drain bolts Use whichever side is accessible 3 Drain Engine oil Place the o...

Page 28: ... filter cover nut 1 Air filter cover 2 Air filter element nut 3 2 Remove Air filter element 4 0 10 30 50 70 90 110130 F 20 10 0 10 20 30 40 50 C SAE 10W 40 SAE 10W 30 Recommended oil brand YAMALUBE Available oil grade API SE type or higher JASO MA or MB Available viscosity index 10W 30 or 10W 40 Engine oil quantity 1 0 L 1 06 US qt 0 88 Imp qt Be sure not to run the engine without air filter eleme...

Page 29: ... cover nut MUFFLER 1 Remove Spark arrester screw 1 Do not wash the element with gasoline or with acidic alkalic or organic solvents Do not wring out the element This could cause it to tear WARNING NOTICE Air filter element nut 0 9 N m 0 09 kgf m 0 66 lb ft Air filter cover nut 1 6 N m 0 16 kgf m 1 2 lb ft The engine and muffler will be very hot after the engine has been run Avoid touching the engi...

Page 30: ...on page 3 6 4 Decarbonize Muffler Tap on the muffler in the area shown in the illustra tion to loosen carbon buildup and then shake it out from the end of the muffler 5 Decarbonize Spark arrester 1 Do not use a wire to clean otherwise the noise damp ing material may come out and the damping effect may be reduced NOTICE When cleaning with a wire brush use it softly to avoid damage or scratch the sp...

Page 31: ...r Spark arrester screw TIP Align the spark arrester lump a with the hole b in the muffler pipe FUEL TANK FILTER 1 Remove Fuel tank cap canister 1 Fuel tank filter 2 a b Spark arrester screw 1 8 N m 0 18 kgf m 1 3 lb ft T R Do not smoke and keep away from open flames sparks or any other source of fire when handling or in the vicinity of fuel WARNING 1 2 ...

Page 32: ...ainer cup 1 Gasket 2 Fuel cock strainer 3 3 Check Fuel cock strainer Damage Replace Dirt clog Clean TIP Clean the fuel cock strainer with clean gasoline and then dry it thoroughly 4 Install Fuel cock strainer Gasket Strainer cup Make sure that the tank cap is tightened securely Do not smoke and keep away from open flames sparks or any other source of fire when handling or in the vicinity of fuel W...

Page 33: ...n page 3 22 2 Eliminate Carbon deposits Refer to CHECKING THE CYLINDER HEAD on page 3 24 3 Install Cylinder head assembly Refer to INSTALLING THE CYLINDER HEAD ASSEMBLY on page 3 25 ADJUSTING THE VALVE CLEARANCE 1 Remove Spark plug cap 1 Spark plug 2 2 Remove Breather hose 3 Cylinder head cover 4 Cylinder head cover gasket 1 1 2 3 4 Before removing the spark plug use compressed air to clean the cy...

Page 34: ...wn enough to be touched 5 Adjust 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 b Using the tappet adjusting tool 2 turn the adjuster 3 in or out to obtain the proper valve clearance Move the thickness gauge up and down to check for the proper resistance Feeler gauge set YU 26900 9 Thickness gauge 90...

Page 35: ...ne for several minutes 2 Attach Digital tachometer 1 3 Measure High engine speed with no load Out of specification Adjust Adjuster Valve clearance Turn clockwise Decrease Turn counterclockwise Increase Valve adjuster locknut 7 N m 0 7 kgf m 5 2 lb ft Cylinder head cover bolt 11 N m 1 1 kgf m 8 1 lb ft Spark plug 20 N m 2 0 kgf m 15 lb ft T R New T R T R 1 Digital tachometer YU 39951 B 90890 06760 ...

Page 36: ...gh engine speed 4 Measure Low engine speed with no load Out of specification Adjust Measurement steps a Move the throttle lever 1 to the low engine speed position a b Check the low engine speed ADJUSTING THE ENGINE SPEED 1 Warm up the engine for several minutes 2 Attach Digital tachometer 1 1 a Low engine speed 1900 2100 r min 1 a 1 Digital tachometer YU 39951 B 90890 06760 ...

Page 37: ... 2 to direction a until it stops e Turn the throttle stop screw 3 carburetor in direc tion c or d until the low engine speed is obtained RECOIL STARTER 1 Check Recoil starter operate smoothly Rough movement Replace the defective part s Refer to CHECKING THE RECOIL STARTER on page 3 9 1 2 a b High engine speed 3750 3850 r min Direction a High engine speed is decreased Direction b High engine speed ...

Page 38: ... 4 5 6 7 8 9 10 PERIODIC CHECKS AND ADJUSTMENTS PERIODIC MAINTENANCE FITTINGS AND FASTENERS 1 Check All fittings and fasteners Looseness Tighten Rough movement Replace the defective part s Damage pitting Replace ...

Page 39: ...n the compression gauge Out of specification Refer to the testing steps Testing steps below the minimum specification a Squirt a few drops of oil into the cylinder b Measure the compression again Before removing the spark plug use compressed air to clean the cylinder head cover to prevent dirt from falling into the engine NOTICE 1 2 Engine compression tester YU 33223 Compression gauge 90890 03081 ...

Page 40: ...piston crown for carbon deposits Carbon deposits Eliminate 5 Install Spark plug Spark plug cap Reading Diagnosis Higher than without oil Worn cylinder piston and piston ring s Same as without oil Defective piston piston ring s valve s and cylinder head gasket Improper valve timing and valve clearance Spark plug 20 N m 2 0 kgf m 15 lb ft T R ...

Page 41: ...ts in the order listed 1 Air filter cover nut 1 2 Air filter cover 1 3 Air filter element nut 1 4 Air filter element case 1 5 Air filter element 1 6 Air filter case 1 7 Breather hose 1 8 Duct 1 9 Gasket 1 1 2 3 4 5 6 7 8 9 0 9 N m 0 09 kgf m 0 66 lb ft 1 6 N m 0 16 kgf m 1 2 lb ft 7 N m 0 7 kgf m 5 2 lb ft 9 N m 0 9 kgf m 6 6 lb ft ...

Page 42: ...uel hose 1 Turn the fuel cock lever to the OFF position 2 Fuel tank 1 3 Fuel tank stay 1 1 4 Fuel tank stay 2 1 5 Fuel tank cap 1 6 Fuel cock assembly 1 3 2 4 5 6 1 10 N m 1 0 kgf m 7 4 lb ft 10 N m 1 0 kgf m 7 4 lb ft 0 8 N m 0 08 kgf m 0 59 lb ft 1 3 N m 0 13 kgf m 0 95 lb ft 29 N m 2 9 kgf m 21 lb ft 29 N m 2 9 kgf m 21 lb ft 6 N m 0 6 kgf m 4 4 lb ft ...

Page 43: ...3 5 1 2 3 4 5 6 7 8 9 10 ENGINE FUEL TANK CHECKING THE FUEL TANK CAP CANISTER 1 Check Fuel tank cap canister 1 Cracks damage Replace 1 ...

Page 44: ...ng the muffler Remove the parts in the order listed Fuel tank Refer to FUEL TANK on page 3 4 1 Muffler 1 2 Gasket 1 3 Muffler cover 1 4 Spark arrester 1 3 1 2 4 10 N m 1 0 kgf m 7 4 lb ft 10 N m 1 0 kgf m 7 4 lb ft 1 8 N m 0 18 kgf m 1 3 lb ft 20 N m 2 0 kgf m 15 lb ft 20 N m 2 0 kgf m 15 lb ft ...

Page 45: ...porarily tighten the nut 1 nut 2 and bolt 3 until just comes in contact with the surface 2 Tighten Muffler nut 1 Muffler nut 2 Muffler bolt 3 TIP Tighten the nuts and bolt to the specified torque in order of muffler nut 1 muffler nut 2 and muffler bolt 3 2 1 3 New Muffler nut 20 N m 2 0 kgf m 15 lb ft Muffler bolt 20 N m 2 0 kgf m 15 lb ft T R T R ...

Page 46: ...l starter Remove the parts in the order listed 1 Recoil starter assembly 1 2 Starter handle 1 3 Drive plate 1 4 Clip 1 5 Drive pawl 2 6 Spring 2 7 Compression spring 1 8 Sheave drum 1 9 Starter spring 1 10 Starter case 1 11 Starter rope 1 1 2 3 4 5 5 6 6 7 8 9 10 11 5 4 N m 0 54 kgf m 3 9 lb ft 7 N m 0 7 kgf m 5 2 lb ft ...

Page 47: ...g preload before removing the drive plate screw 1 Hook the rope into the sheave drum slot a and turn the sheave drum assembly clockwise 3 Remove Sheave drum assembly 1 Starter spring 2 Starter rope CHECKING THE RECOIL STARTER 1 Check Starter rope Wear damage Replace Starter case Cracks damage Replace Starter spring Dirt Clean and apply grease Wear damage Replace a b 1 1 a 1 2 Be sure to press down...

Page 48: ...ing 2 Sheave drum 3 TIP Engage the spring hook a with the drum slit then wind the spring counterclockwise into the drum from the larger to the smaller diameter 2 Install Sheave drum assembly TIP Engage the spring hook a with the starter case hook b 3 Install Springs 1 Drive pawls 2 TIP Set the ends of the springs 1 outside the drive pawls 2 4 Install Compression spring 1 Drive plate Clip 2 3 1 4 2...

Page 49: ...ave drum slot a and turn the sheave drum assembly counterclockwise four times and then unhook the starter rope from the slot 6 Check Starter handle TIP Pull the starter handle several times to check that the sheave drum turns smoothly and to check the starter rope for slack Repeat steps 1 5 if necessary a 1 Drive plate screw 5 4 N m 0 54 kgf m 3 9 lb ft T R ...

Page 50: ...o AIR FILTER on page 3 3 Fuel tank Refer to FUEL TANK on page 3 4 Carburetor Refer to REMOVING THE CARBURETOR on page 4 1 Recoil starter Refer to RECOIL STARTER on page 3 8 1 Flywheel cover 1 2 TCI unit 1 3 Starter pulley 1 4 Flywheel 1 5 Woodruff key 1 1 2 3 4 5 10 N m 1 0 kgf m 7 4 lb ft 7 N m 0 7 kgf m 5 2 lb ft 7 N m 0 7 kgf m 5 2 lb ft 100 N m 10 kgf m 74 lb ft ...

Page 51: ...e flywheel 3 Remove Flywheel 1 Woodruff key TIP Remove the flywheel 1 using the flywheel puller 2 Fully tighten the tool holding bolts making sure the tool body is parallel with the flywheel If necessary one bolt may be backed out slightly to level the tool body 1 2 Primary clutch holder YS 01880 A Sheave holder 90890 01701 1 2 Heavy duty puller YU 33270 B Flywheel puller 90890 01362 ...

Page 52: ...to hold the flywheel 3 Install TCI unit Refer to INSTALLING THE TCI UNIT on page 3 14 Flywheel cover INSTALLING THE TCI UNIT 1 Install TCI unit TCI unit bolts 1 2 Flywheel nut 100 N m 10 kgf m 74 lb ft Primary clutch holder YS 01880 A Sheave holder 90890 01701 T R TCI unit bolt 10 N m 1 0 kgf m 7 4 lb ft Flywheel cover bolt 7 N m 0 7 kgf m 5 2 lb ft T R T R TCI unit bolt 10 N m 1 0 kgf m 7 4 lb ft...

Page 53: ...ir gap Adjustment steps a Loosen the TCI unit bolts 1 b Adjust the TCI unit air gap c Tighten the TCI unit bolts 1 Feeler gauge set YU 26900 9 Thickness gauge 90890 03180 TCI unit air gap 0 4 0 6 mm 0 0157 0 0236 in 1 Feeler gauge set YU 26900 9 Thickness gauge 90890 03180 TCI unit bolt 10 N m 1 0 kgf m 7 4 lb ft T R ...

Page 54: ...listed Fuel tank Refer to FUEL TANK on page 3 4 Fuel tank stay Refer to FUEL TANK on page 3 4 Engine switch and oil warning unit Refer to ENGINE SWITCH AND OIL WARNING UNIT on page 3 21 1 Spring 1 2 Link rod 1 3 Spring 1 4 Governor arm 1 5 Throttle lever assembly 1 3 4 2 1 5 1 1 N m 0 11 kgf m 0 81 lb ft 7 N m 0 7 kgf m 5 2 lb ft 7 N m 0 7 kgf m 5 2 lb ft 8 N m 0 8 kgf m 5 9 lb ft ...

Page 55: ... the parts in the order listed Fuel tank Refer to FUEL TANK on page 3 4 Fuel tank stay Refer to FUEL TANK on page 3 4 Engine switch and oil warning unit Refer to ENGINE SWITCH AND OIL WARNING UNIT on page 3 21 Crankcase cover Refer to PISTON CAMSHAFT CRANK CASE AND CRANKSHAFT on page 3 32 1 Clip 1 2 Governor fork 1 3 Flyweight shaft assembly 1 3 2 1 ...

Page 56: ...weight shaft assembly 1 Washer 2 TIP Remove the flyweight shaft assembly by tapping the weight shaft from outside of the crankcase cover DISASSEMBLING THE FLYWEIGHT SHAFT ASSEMBLY 1 Remove Flyweight shafts 1 Weights 2 Collar 3 Washer 4 Circlip 5 Weight shaft 6 CHECKING THE FLYWEIGHT SHAFT ASSEMBLY 1 Check Flyweight shaft assembly move smoothly Rough movement Replace 3 1 3 2 1 2 1 2 3 4 5 6 1 1 ...

Page 57: ...EMBLY 1 Install Weight shaft 1 Circlip 2 Washer 3 Collar 4 Weights 5 Flyweight shafts 6 INSTALLING THE FLYWEIGHT SHAFT ASSEMBLY AND GOVERNOR FORK 1 Install Washer 1 Flyweight shaft assembly 2 2 Install Washers 1 Governor fork 2 Clip 3 3 Install Governor assembly Crankcase cover Refer to INSTALLING THE CRANKCASE COVER on page 3 36 6 6 6 5 4 3 2 1 New 1 2 3 1 1 2 ...

Page 58: ...on page 3 20 ADJUSTING THE GOVERNOR 1 Adjust Governor Adjustment steps a Loosen the governor arm bolt 1 b Turn the governor arm 2 clockwise until it stops c Turn the governor fork 3 clockwise until it stops d Tighten the governor arm bolt 1 1 2 3 Governor arm bolt 8 N m 0 8 kgf m 5 9 lb ft T R ...

Page 59: ...h and oil warning unit Remove the parts in the order listed Fuel tank Refer to FUEL TANK on page 3 4 Fuel tank stay Refer to FUEL TANK on page 3 4 1 Plastic locking tie 1 With oil warning model 2 Oil warning unit 1 With oil warning model 3 Engine switch 1 4 Wire harness protector 1 With oil warning model 1 2 3 4 7 N m 0 7 kgf m 5 2 lb ft 4 5 N m 0 45 kgf m 3 3 lb ft ...

Page 60: ...n page 3 6 Air filter Refer to AIR FILTER on page 3 3 Carburetor Refer to REMOVING THE CARBURETOR on page 4 1 Flywheel cover Refer to FLYWHEEL on page 3 12 1 Spark plug cap 1 2 Spark plug 1 3 Cylinder head cover 1 4 Cylinder head cover gasket 1 5 Cylinder air shroud 1 6 Locknut 2 7 Adjuster 2 8 Screw 2 5 4 3 2 6 7 8 6 7 8 1 11 N m 1 1 kgf m 8 1 lb ft 2 3 N m 0 23 kgf m 1 7 lb ft 7 N m 0 7 kgf m 5 ...

Page 61: ...ocker arm shaft 2 10 Rocker arm 2 11 Push rod 2 12 Cylinder head assembly 1 13 Cylinder head gasket 1 14 Dowel pin 2 10 11 9 10 12 14 13 11 9 11 N m 1 1 kgf m 8 1 lb ft 2 3 N m 0 23 kgf m 1 7 lb ft 7 N m 0 7 kgf m 5 2 lb ft 20 N m 2 0 kgf m 15 lb ft 50 N m 5 0 kgf m 37 lb ft 12 N m 1 2 kgf m 8 9 lb ft 1st 2nd ...

Page 62: ... Check the combustion chamber for carbon depos its Any carbon deposits Eliminate TIP Be sure not to damage the contact surface of the cylinder 2 Check Cylinder head Cracks damage around the hole of spark plug Replace 3 Measure Cylinder head warpage TIP Measure the warpage on the contact surface of the cylin der head at six points using the straight edge and thick ness gauge Out of specifications R...

Page 63: ...INSTALLING THE CYLINDER HEAD ASSEMBLY 1 Install Cylinder head Cylinder head bolts 1 to 5 TIP Tighten the bolts to the specified torque in two steps and in order from 1 to 5 2 4 1 5 3 5 Cylinder head bolt 1st 12 N m 1 2 kgf m 8 9 lb ft 2nd 50 N m 5 0 kgf m 37 lb ft T R ...

Page 64: ...Removing the valve Remove the parts in the order listed Cylinder head assembly Refer to CYLINDER HEAD COVER CYLIN DER HEAD on page 3 22 1 Valve cotter 2 2 Valve spring retainer 2 3 Valve spring 2 4 Exhaust valve 1 5 Intake valve 1 6 Valve stem seal 1 Intake side only 1 2 3 5 6 4 1 2 3 ...

Page 65: ...5 CHECKING THE VALVES AND VALVE SPRINGS The following procedure applies to all of the valves valve springs and related components 1 Measure Valve stem length a Valve head diameter b Out of specifications Replace 5 1 2 3 4 Do not compress the valve spring more than neces sary Valve spring compressor 90890 01253 NOTICE b a Valve stem length Intake 90 0 mm 3 5433 in Valve stem length Exhaust 90 3 mm ...

Page 66: ...ce 5 Measure Compressed valve spring force a Out of specification Replace a Valve stem diameter Intake 5 948 5 963 mm 0 2342 0 2348 in Valve stem diameter Exhaust 5 940 5 955 mm 0 2339 0 2344 in Limit Intake 5 918 mm 0 2330 in Limit Exhaust 5 910 mm 0 2327 in Valve stem runout limit 0 01 mm 0 0004 in a Valve spring free length Intake 36 2 mm 1 4252 in Valve spring free length Exhaust 36 2 mm 1 425...

Page 67: ...f the valves and valve seats 1 Remove carbon deposits from the valve face and valve seat 2 Apply a small amount of coarse mechanic s blue lay out fluid to the valve face a Installed compression spring force Intake 91 20 104 93 N 9 12 10 49 kgf 20 50 23 59 lbf Installed compression spring force Exhaust 91 20 104 93 N 9 12 10 49 kgf 20 50 23 59 lbf Installed length Intake 29 0 mm 1 1417 in Installed...

Page 68: ...at the contact width along the entire valve seat is within specifications Out of specification rough eccentric wear Replace VALVE LAPPING 1 Apply a coarse lapping compound evenly on the valve face Lap the valve by tapping and rotating the valve lapper 1 clockwise and counterclockwise a Valve face contact width Intake 0 7 0 9 mm 0 0276 0 0354 in Valve face contact width Exhaust 0 7 0 9 mm 0 0276 0 ...

Page 69: ...edure applies to all of the valves valve springs and related components 1 Install Valve stem seal Intake side only Valve 1 Valve spring 2 Valve spring retainer 3 Valve cotter 4 Use the valve spring compressor 5 to install the parts Do not let the lapping compound enter the gap between the valve stem and the valve guide NOTICE 5 M E 4 3 2 1 Valve spring compressor 90890 01253 New New a b Do not com...

Page 70: ...d assembly Refer to CYLINDER HEAD COVER CYLIN DER HEAD on page 3 22 Flywheel Refer to FLYWHEEL on page 3 12 1 Crankcase cover 1 2 Gasket 1 3 Dowel pin 2 4 Clamp 1 With oil warning model 5 Oil level switch 1 With oil warning model 6 Flyweight shaft assembly 1 7 Governor fork 1 1 2 3 3 4 5 6 7 10 N m 1 0 kgf m 7 4 lb ft 10 N m 1 0 kgf m 7 4 lb ft 27 N m 2 7 kgf m 20 lb ft 27 N m 2 7 kgf m 20 lb ft 3...

Page 71: ...ANKSHAFT Order Job Parts to remove Q ty Remarks 8 Camshaft 1 9 Valve lifter 2 10 Connecting rod cap 1 11 Crankshaft 1 12 Connecting rod 1 13 Piston pin circlip 2 14 Piston pin 1 15 Piston 1 16 Piston ring set 1 9 11 10 12 13 14 15 16 13 9 8 20 N m 2 0 kgf m 15 lb ft ...

Page 72: ...LVE LIFTER 1 Remove Camshaft 1 TIP Remove the camshaft 1 when the camshaft gear mark b and the crankshaft gear mark a are aligned 2 Remove Intake valve lifter 1 Exhaust valve lifter 2 CHECKING THE CAMSHAFT 1 Check Camshaft Crack damage wear Replace 2 Check Camshaft lobe dimensions a and b b a 1 1 2 a b ...

Page 73: ...VE LIFTER 1 Check Valve lifter Damage Replace Camshaft lobe dimensions Lobe height a Intake 32 1 32 2 mm 1 2638 1 2677 in Limit 31 9 mm 1 2559 in Lobe height a Exhaust 32 5 32 6 mm 1 2795 1 2835 in Limit 32 3 mm 1 2717 in Base circle diameter b Intake 25 98 26 08 mm 1 0228 1 0268 in Limit 25 78 mm 1 015 in Base circle diameter b Exhaust 26 03 26 13 mm 1 0248 1 0287 in Limit 25 83 mm 1 0169 in a a ...

Page 74: ...se cover Damage Replace Bearing Noise wear rotational failure Replace INSTALLING THE CRANKCASE COVER 1 Install Crankcase cover Crankcase cover bolts 1 to 8 TIP Tighten the bolts to the specified torque in two steps and in order from 1 to 8 1 2 b a 1 Be sure to align the camshaft 1 gear mark b with the crankshaft gear mark a NOTICE 1 5 3 7 2 6 4 8 8 Crankcase cover bolt 1st 12 N m 1 2 kgf m 8 9 lb ...

Page 75: ...act surface of the cylin der head at six points using a straight edge and feeler gauge set Out of specification Replace the crankcase assembly 3 Measure Piston to cylinder clearance a Measure cylinder bore C with the cylinder bore gauge TIP Measure cylinder bore C by taking side to side and front to back measurements of the cylinder Feeler gauge set YU 26900 9 Thickness gauge 90890 03180 Warpage l...

Page 76: ... set e Calculate the piston to cylinder clearance with the following formula f If out of specification replace the crankcase assembly and replace the piston and piston rings as a set CHECKING THE CRANKCASE 1 Check Crankcase Damage Replace Bearing Noise wear rotational failure Replace C maximum of D1 D2 D3 D4 D5 D6 P a Piston diameter 79 96 79 98 mm 3 1480 3 1488 in Limit 79 91 mm 3 1461 in Piston ...

Page 77: ... piston check the pis ton pin hole If there is any protrusion use a knife or scraper to gently remove it so that piston pin can be pushed in smoothly with your fingers CHECKING THE PISTON RINGS The following procedure applies to all of the piston rings 1 Measure Piston ring side clearance Out of specification Replace the piston and pis ton rings as a set TIP Before measuring the piston ring side c...

Page 78: ...specification Replace the piston rings as a set Piston ring Top ring Side clearance 0 03 0 05 mm 0 0011 0 0019 in Limit 0 10 mm 0 0039 in 2nd ring Side clearance 0 02 0 04 mm 0 0007 0 0015 in Limit 0 10 mm 0 0039 in a b b Upper of cylinder Top ring End gap installed 0 20 0 35 mm 0 0079 0 0138 in Limit 0 60 mm 0 0236 in 2nd ring End gap installed 0 20 0 35 mm 0 0079 0 0138 in Limit 0 70 mm 0 0275 i...

Page 79: ...ut of specification Replace Use a micrometer CHECKING THE CONNECTING ROD OIL CLEARANCE TIP Measure the oil clearance if replacing the crankshaft or connecting rod 1 Place a piece of Plastigauge 1 on the crank pin horizontally TIP Wipe off oil thoroughly from the crankshaft connecting rod and connecting rod cap 1 Dial indicator gauge YU A8428 Dial gauge 90890 03097 Runout limit 0 8 mm 0 0315 in a C...

Page 80: ...on Replace crankshaft or con necting rod assembly and then measure the clear ance again TIP Measure the widest portion of the pressed Plastigauge INSTALLING THE PISTON AND PISTON RING 1 Install Top ring 1 2nd ring 2 Oil ring 3 TIP Be sure to install the top ring and 2nd ring so that the R mark a faces toward the piston head Make sure that the piston rings move smoothly 1 2 Connecting rod cap bolt ...

Page 81: ... the piston pin circlips so that the clip ends are 45 c or more from the cutout in the piston INSTALLING THE CRANKSHAFT 1 Make sure that the end gap of each piston ring is positioned correctly as shown in the illustration 2 Install Piston with the connecting rod 1 3 Attach Piston ring compressor 1 TIP Attach the piston ring compressor to the piston and then insert the piston into the cylinder b a ...

Page 82: ...e cover 5 Install Crankshaft 1 6 Install Connecting rod cap 1 Connecting rod cap bolts 2 TIP Make sure that the mark a on the connecting rod is aligned with the mark b on the connecting rod cap Tighten the connecting rod cap bolts alternately two to three times 7 Install Camshaft Refer to INSTALLING THE VALVE LIFTER AND CAMSHAFT on page 3 36 Crankcase cover Refer to INSTALLING THE CRANKCASE COVER ...

Page 83: ...rder Job Parts to remove Q ty Remarks Removing the carburetor Remove the parts in the order listed Fuel tank Refer to FUEL TANK on page 3 4 Air filter Refer to AIR FILTER on page 3 3 1 Carburetor assembly 1 2 Link rod 1 3 Spring 1 4 Gasket 1 5 Joint 1 6 Gasket 1 2 1 4 5 6 3 ...

Page 84: ...er bolt 1 3 Gasket 1 4 Float chamber 1 5 Gasket 1 6 Float pin 1 7 Float 1 8 Needle assembly 1 9 Main nozzle 1 10 Throttle valve 1 11 Throttle stop screw Spring 1 1 12 Pilot jet 1 13 Throttle shaft 1 14 Choke valve 1 15 Choke lever 1 1 2 3 4 5 7 6 8 9 12 11 10 13 14 15 0 7 N m 0 07 kgf m 0 52 lb ft 0 7 N m 0 07 kgf m 0 52 lb ft 1 6 N m 0 16 kgf m 1 2 lb ft 1 3 N m 0 13 kgf m 0 95 lb ft 1 1 N m 0 11...

Page 85: ...ce TIP Lift up the float so that the tip of the float valve lightly contacts the float arm and then measure the float height a Do not adjust the float height 2 Check Jets Carburetor body Clogged Apply compressed air to clean the jet 3 Check Valve seat Wear damage Replace Dirt Clean a Float height 13 8 mm 0 54 in a b a Wear at groove b Dirt ...

Page 86: ...5 1 1 2 3 4 5 6 7 8 9 10 ELECTRICAL ELECTRICAL CIRCUIT DIAGRAM B B B B B B B B W Y 1 2 3 4 5 ...

Page 87: ...5 2 1 2 3 4 5 6 7 8 9 10 ELECTRICAL CIRCUIT DIAGRAM Color code 1 Spark plug 2 TCI unit 3 Oil warning unit 4 Oil level switch 5 Engine switch B Black B W Black White Y Yellow ...

Page 88: ...5 3 1 2 3 4 5 6 7 8 9 10 ELECTRICAL ELECTRICAL COMPONENTS ELECTRICAL COMPONENTS 1 Spark plug 2 TCI unit 3 Oil warning unit 4 Engine switch 5 Oil level switch 1 2 3 4 5 ...

Page 89: ...ween the switch positions a few times Measurement example of the electric components CHECKING THE IGNITION SPARK GAP 1 Check Engine oil level Insufficient Add the engine oil Refer to ENGINE OIL LEVEL on page 2 4 Ω O L Never insert the tester probes into the coupler termi nal slots Always insert the probes from the opposite end of the coupler taking care not to loosen or dam age the leads Model 88 ...

Page 90: ... is operating normally a Disconnect the spark plug cap 1 from the spark plug b Connect the ignition checker 2 as shown c Connect the ignition checker lead to spark plug 3 as shown d Set the engine switch to ON e Pull the recoil starter handle f Measure the ignition spark gap a CHECKING THE SPARK PLUG CAP RESISTANCE 1 Remove Spark plug cap 2 Check Spark plug cap resistance Out of specification Repl...

Page 91: ... and TCI unit Out of specification Perform the TCI unit adjust ment steps Refer to INSTALLING THE TCI UNIT on page 3 14 CHECKING THE IGNITION COIL TCI UNIT PRIMARY RESISTANCE 1 Check Primary coil resistance Out of specification Replace 1 2 Model 88 Multimeter with tachometer YU A1927 Digital circuit tester CD732 90890 03243 Positive tester probe Spark plug side 1 Negative tester probe High tension...

Page 92: ...place a Remove the ignition coil TCI unit b Connect the digital circuit tester to the second ary terminal c Measure the secondary coil resistance 1 2 Model 88 Multimeter with tachometer YU A1927 Digital circuit tester CD732 90890 03243 Positive tester probe Black White 1 Negative tester probe Body ground 2 Secondary coil resistance 11 7 k 1 2 Model 88 Multimeter with tachometer YU A1927 Digital ci...

Page 93: ...rom the bottom of the crankcase cover 2 Check Oil level switch continuity Out of specification Replace a Connect the digital circuit tester to the oil level switch as shown 1 2 a b Model 88 Multimeter with tachometer YU A1927 Digital circuit tester CD732 90890 03243 Positive tester probe Black 1 Negative tester probe Black 2 Engine switch ON Continuity a Engine switch OFF No continuity b 1 1 2 2 M...

Page 94: ... 5 6 7 8 9 10 ELECTRICAL ELECTRICAL COMPONENTS b Check the oil level switch continuity CHECKING THE WIRE HARNESS 1 Check Terminal of the connector Contamination rust or disconnection Clean or replace the connector ...

Page 95: ...HECKING THE IGNITION COIL TCI UNIT PRIMARY RESISTANCE on page 5 6 Replace the ignition coil 10 Check the spark plug cap resistance Refer to CHECKING THE SPARK PLUG CAP RESIS TANCE on page 5 5 Replace the spark plug cap 11 Check the carburetor for clogged passages or fuel overflow Clean 12 Check the compression pressure Refer to MEASURING THE COMPRESSION PRES SURE on page 3 1 Too high Decarbonize t...

Page 96: ...r throttle shaft Tighten the carburetor nuts securely Replace the carburetor joint or gasket with a new one 6 Check the compression pressure Refer to MEASURING THE COMPRESSION PRES SURE on page 3 1 Too high Decarbonize the combustion chamber if there is carbon deposits Too low Next checking steps 7 Check the valve clearance Refer to ADJUSTING THE VALVE CLEARANCE on page 2 11 Adjust the valve clear...

Page 97: ...CE on page 2 11 Adjust the valve clearance 5 Check the valve face and valve seat for wear Refer to VALVE on page 3 26 Resurface or replace the valve face and valve seat 6 Check if the marks on the crankshaft and camshaft are aligned Refer to INSTALLING THE VALVE LIFTER AND CAM SHAFT on page 3 36 Correct 7 Check if there is seizure wear or damage on the piston piston ring or cylinder Refer to PISTO...

Page 98: ...just or replace 7 Check if there is air suction from the carburetor joint gas ket or throttle shaft Tighten the carburetor nuts securely Replace the carburetor joint or gasket with a new one 8 Check if the slow or main passages such as pilot jet and main jet in the carburetor are clogged Clean the parts 9 Check the valve clearance Refer to ADJUSTING THE VALVE CLEARANCE on page 2 11 Adjust the valv...

Page 99: ...the governor link operate smoothly Adjust or replace 2 Check that the governor spring is stretched Replace 3 Check the governor adjustment Refer to ADJUSTING THE GOVERNOR on page 3 20 Adjust 4 Check the governor weight and governor bushing function Refer to CHECKING THE FLYWEIGHT SHAFT ASSEM BLY on page 3 18 Adjust or replace ...

Page 100: ...6 6 1 2 3 4 5 6 7 8 9 10 TROUBLESHOOTING GOVERNOR OPERATION MEMO ...

Page 101: ...t output 6 4 kW 8 7 PS MX250 7 0 kW 9 5 PS MX300 Fuel Fuel Unleaded gasoline Gasohol E10 acceptable Fuel tank capacity 5 5 L 1 45 US gal 1 21 Imp gal Engine oil quantity 1 0 L 1 06 US qt 0 88 Imp qt Recommended oil brand YAMALUBE Available oil grade API SE type or higher JASO MA or MB Available viscosity index 10W 30 or 10W 40 Lubrication system Forced splashing Air filter system Semi wet Cooling ...

Page 102: ... output tested on an engine model and measured at 3600 r min Actual power output for an installed engine will vary depending on numerous factors including the operating speed of the engine environmental conditions and other variables Use only unleaded gasoline The use of leaded gasoline will cause severe damage to internal engine parts NOTICE ...

Page 103: ...pin diameter 18 995 19 000 mm 0 7478 0 7480 in Limit 18 975 mm 0 7470 in Piston ring Top ring Type Barrel Dimensions 1 2 2 9 mm 0 0472 0 1141 in End gap installed 0 20 0 35 mm 0 0079 0 0138 in Limit 0 60 mm 0 0236 in Side clearance 0 03 0 05 mm 0 0011 0 0019 in Limit 0 10 mm 0 0039 in 2nd ring Type Taper Dimensions 1 2 3 2 mm 0 0472 0 1260 in End gap installed 0 20 0 35 mm 0 0079 0 0138 in Limit 0...

Page 104: ... circle diameter Intake 25 98 26 08 mm 1 0228 1 0268 in Limit 25 78 mm 1 015 in Base circle diameter Exhaust 26 03 26 13 mm 1 0248 1 0287 in Limit 25 83 mm 1 0169 in Camshaft journal diameter 15 965 15 990 mm 0 6285 0 6295 in Limit 15 950 mm 0 628 in Valve Valve dimensions Valve head diameter Intake 31 9 32 1 mm 1 2559 1 2638 in Valve head diameter Exhaust 28 9 29 1 mm 1 1377 1 1456 in Valve stem ...

Page 105: ...in Valve clearance cold Intake 0 05 0 09 mm 0 0020 0 0035 in Exhaust 0 05 0 09 mm 0 0020 0 0035 in Push rod Runout limit 0 15 mm 0 0059 in Valve spring Valve spring free length Intake 36 2 mm 1 4252 in Valve spring free length Exhaust 36 2 mm 1 4252 in Limit Intake 34 39 mm 1 3539 in Limit Exhaust 34 39 mm 1 3539 in Installed length Intake 29 0 mm 1 1417 in Installed length Exhaust 29 0 mm 1 1417 ...

Page 106: ...seat size 1 6 mm 0 062 in Main nozzle 6B MX250 6A MX300 Pilot jet 0 41 mm 0 016 in MX250 0 44 mm 0 017 in MX300 Pilot screw 1 5 8 turns out MX250 2 turns out MX300 Throttle valve 18 Float height 13 8 mm 0 54 in Governor arm Tension spring attach hole 2 Engine speed High engine speed 3750 3850 r min Low engine speed 1900 2100 r min ...

Page 107: ...ELECTRICAL Ignition system Ignition timing at 3600 r min BTDC 20 3 Primary coil resistance 0 8 20 Secondary coil resistance 11 7 k 20 Spark plug cap resistance 3 75 6 25 k at 20 68 F TCI unit air gap 0 4 0 6 mm 0 0157 0 0236 in Minimum ignition spark gap 6 0 mm 0 24 in ...

Page 108: ... 1 5 100 N m 10 kgf m 74 lb ft Governor arm bolt M6 1 0 8 N m 0 8 kgf m 5 9 lb ft Throttle lever assembly bolt M6 1 0 7 N m 0 7 kgf m 5 2 lb ft Throttle lever assembly plate screw M5 0 8 1 1 N m 0 11 kgf m 0 81 lb ft Throttle lever assembly wire screw M4 0 7 1 1 N m 0 11 kgf m 0 81 lb ft Oil warning unit bolt M6 1 0 7 N m 0 7 kgf m 5 2 lb ft Engine switch screw M6 1 0 4 5 N m 0 45 kgf m 3 3 lb ft ...

Page 109: ...ONS TIGHTENING TORQUES Pilot jet 1 1 N m 0 11 kgf m 0 81 lb ft Throttle valve screw 0 7 N m 0 07 kgf m 0 52 lb ft Choke valve screw 0 7 N m 0 07 kgf m 0 52 lb ft Main nozzle 1 6 N m 0 16 kgf m 1 2 lb ft Item Thread size Tightening torque ...

Page 110: ... assemblies are included in the applicable sections of this book To avoid warpage tighten multi fastener assemblies in a crisscross fashion in progressive stages until full torque is reached Unless otherwise specifications call for clean dry threads Components should be at room temperature Thread size Tightening torque N m kgf m lb ft M4 2 0 2 1 5 M5 3 0 3 2 2 M6 7 0 7 5 2 M7 10 1 0 7 4 M8 15 1 5 ...

Page 111: ...ng Connecting rod big end Crank pin Crankshaft journal Connecting rod cap bolt Piston pin Piston Crankshaft gear teeth Valve stem Valve stem end Valve rocker arm shaft Valve push rod end Valve lifter stem Camshaft lobe Camshaft gear teeth Decompressor pin Camshaft journal Governor collar internal surface Governor fork meet surface Governor weight moving point LS E E E E E E E E E E E E E E E E E E...

Page 112: ...7 12 1 2 3 4 5 6 7 8 9 10 SPECIFICATIONS WIRE ROUTING DIAGRAM WIRE ROUTING DIAGRAM UPPER SIDE VIEW ...

Page 113: ...switch A The spark plug cap should face the direction indicated in the illustration B Route the lead as shown C The lead is black and the protector is gray D Make sure that the gap between the end of the wire harness protector and end of the crankcase is 20 mm 0 79 in or more E Fasten the ground terminal and engine switch together F Screw in the high tension cord until it touches the spark plug ca...

Page 114: ...7 14 1 2 3 4 5 6 7 8 9 10 SPECIFICATIONS WIRE ROUTING DIAGRAM ENGINE SWITCH AND OIL WARNING UNIT ...

Page 115: ...rning unit 4 Clamp A As an indication of the tightening position of the plastic locking tie the terminals are collectively set to the center of the wire harness protector so as to be bundled B Plastic locking tie should be within this range C Clamp the terminals so as not to touch the crankcase D Pass the lead through the hole in the crankcase B Black Y Yellow Gy Gray B W Black White ...

Page 116: ...7 16 1 2 3 4 5 6 7 8 9 10 SPECIFICATIONS WIRE ROUTING DIAGRAM TCI UNIT ...

Page 117: ...CI unit 3 Oil warning unit A Make sure that the high tension cord is not pinched when installing the flywheel cover B Adjust the TCI unit air gap between 0 4 0 6 mm 0 0157 0 0236 in on both sides C Contact between the protector and the edge is permitted but contact between the wire lead and the edge is not permitted B W Black White ...

Page 118: ...7 18 1 2 3 4 5 6 7 8 9 10 SPECIFICATIONS WIRE ROUTING DIAGRAM OIL LEVEL SWITCH CRANKCASE COVER ...

Page 119: ...7 19 1 2 3 4 5 6 7 8 9 10 SPECIFICATIONS WIRE ROUTING DIAGRAM Color code 1 Clamp 2 Oil level switch A Touch the tube gray with the grommet B Route the oil level switch lead as shown B Black Gy Gray ...

Page 120: ...APPENDIX CIRCUIT DIAGRAM B B B B B B B B W Y 1 2 3 4 5 ...

Page 121: ...Color code 1 Spark plug 4 Oil level switch 2 TCI unit 5 Engine switch 3 Oil warning unit B Black B W Black White Y Yellow ...

Page 122: ...MEMO ...

Page 123: ...7VE F8197 10_Cover indd 2 2017 03 16 16 24 50 ...

Page 124: ...SERVICE MANUAL MX250 MX300 7VE F8197 10 LIT 19616 02 45 2017 03 1 7VE F8197 10_Cover indd 1 2017 03 16 16 24 49 ...

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Yamaha MX250, Service Manual

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