MX775, MX800, MX825

SERVICE MANUAL

©2016 by Yamaha Motor

Corporation, U.S.A.

1st Edition, December 2016

All rights reserved. Any reprinting or

unauthorized use without the written

permission of Yamaha Motor

Corporation, U.S.A.

is expressly prohibited.

LIT-19616-02-37

IMPORTANT

This manual was produced by the Yamaha Motor Powered Products Co., Ltd. primarily for use by

Yamaha dealers and their qualified mechanics. It is not possible to include all the knowledge of a

mechanic in one manual. Therefore, anyone who uses this book to perform maintenance and

repairs on Yamaha machines should have a basic understanding of mechanics and the techniques

to repair these types of machines. Repair and maintenance work attempted by anyone without this

knowledge is likely to render the machine unsafe and unfit for use.

This model has been designed and manufactured to perform within certain specifications in regard

to performance and emissions. Proper service with the correct tools is necessary to ensure that the

machine will operate as designed. If there is any question about a service procedure, it is imperative

that you contact a Yamaha dealer for any service information changes that apply to this model. This

policy is intended to provide the customer with 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 Manual contains information regarding periodic maintenance to the emission control

system. Please read this material carefully.

• Designs and specifications are subject to change without notice.

IMPORTANT MANUAL INFORMATION

Particularly important information is distinguished in this manual by the following notations.

This is the safety alert symbol. It is used to alert you to potential personal injury hazards.

Obey all safety messages that follow this symbol to avoid possible injury or death.

A WARNING indicates a hazardous situation which, if not avoided, could result in death or

serious injury.

A NOTICE indicates special precautions that must be taken to avoid damage to the machine

or other property.

TIP

A TIP provides key information to make procedures easier or clearer.

WARNING

NOTICE

HOW TO USE THIS MANUAL

This manual is intended as a handy, easy-to-read reference book for the mechanic.

Comprehensive explanations of all installation, removal, disassembly, assembly, repair and check

procedures are laid out with the individual steps in sequential order.

• The manual is divided into chapters and each chapter is divided into sections. The current section

title is shown at the top of each page “1”.

• Sub-section titles appear in smaller print than the section title “2”.

• To help identify parts and clarify procedure steps, there are exploded diagrams at the start of each

removal and disassembly section “3”.

• Numbers are given in the order of the jobs in the exploded diagram. A number indicates a disas-

sembly step “4”.

• Symbols indicate parts to be lubricated or replaced “5”.

Refer to SYMBOLS.

• A job instruction chart accompanies the exploded diagram, providing the order of jobs, names of

parts, notes in jobs, etc. “6”. This step explains removal procedure only. For installation, reverse

the steps.

• Jobs requiring more information (such as special tools and technical data) are described sequen-

tially “7”.

1

3

7

2

4

5

6

SYMBOLS

The following symbols are used in this manual for easier understanding.

TIP

The following symbols are not relevant 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

GENERAL INFORMATION

PERIODIC CHECKS AND

ADJUSTMENTS

ENGINE

FUEL

ELECTRICAL

TROUBLESHOOTING

SPECIFICATIONS

1

2

3

4

5

6

7

8

9

10

INDEX

MEMO

TABLE OF CONTENTS

GENERAL INFORMATION

MACHINE IDENTIFICATION ......................1-1

SERIAL NUMBER .................................1-1

STARTING SERIAL NUMBER...............1-1

DIMENSIONS .............................................1-2

TOP .......................................................1-2

MOUNTING BASE ................................1-2

REAR.....................................................1-3

REAR (For models equipped with a

muffler) ..................................................1-3

RIGHT SIDE ..........................................1-4

RIGHT SIDE (For models equipped

with a muffler) ........................................1-4

IMPORTANT INFORMATION .....................1-5

PREPARATION FOR REMOVAL AND

DISASSEMBLY......................................1-5

CAUTION ON SERVICE........................1-5

NOTES ON SERVICE ...........................1-5

ALL REPLACEMENT PARTS................1-6

GASKETS, OIL SEALS, AND

O-RINGS ...............................................1-6

BEARINGS AND OIL SEALS ................1-7

BASIC SERVICE INFORMATION ..............1-7

ELECTRICAL SYSTEM.........................1-7

SPECIAL TOOLS AND TESTERS...........1-11

PERIODIC CHECKS AND

ADJUSTMENTS

INTRODUCTION.........................................2-1

MAINTENANCE INTERVALS CHART .......2-1

PERIODIC MAINTENANCE/

LUBRICATION INTERVALS.......................2-1

PERIODIC MAINTENANCE .......................2-2

SPARK PLUGS......................................2-2

MUFFLER

(For models equipped with a muffler) ....2-3

ENGINE OIL LEAKAGE ........................2-4

ENGINE OIL LEVEL..............................2-5

REPLACING THE ENGINE OIL ............2-6

FUEL LEAKAGE....................................2-8

FUEL FILTER ........................................2-8

OIL COOLER ........................................ 2-9

AIR FILTER ELEMENT ......................... 2-9

ADJUSTING THE VALVE

CLEARANCE ........................................ 2-9

CYLINDER HEADS

DECARBONIZATION.......................... 2-13

ENGINE SPEED ................................. 2-14

ADJUSTING THE ENGINE SPEED.... 2-15

LOW ENGINE SPEED (Replace the

throttle body) ....................................... 2-16

FITTINGS AND FASTENERS............. 2-16

ENGINE

ENGINE INSPECTION............................... 3-1

MEASURING THE COMPRESSION

PRESSURE .......................................... 3-1

AIR FILTER ................................................ 3-3

MUFFLER (For models equipped with a

muffler) ...................................................... 3-4

OIL COOLER ............................................. 3-5

REMOVING THE OIL COOLER............ 3-6

CHECKING THE OIL COOLER............ 3-6

INSTALLING THE OIL COOLER .......... 3-6

ECU, RECTIFIER/REGULATOR, AND

FUSES........................................................ 3-8

INSTALLING THE FUSES .................... 3-9

IGNITION COILS...................................... 3-10

CASE AND FAN....................................... 3-11

REMOVING THE CASE AND FAN ..... 3-12

CHECKING THE CASE AND FAN...... 3-13

INSTALLING THE CASE AND FAN .... 3-13

FLYWHEEL AND STATOR COIL

ASSEMBLY .............................................. 3-15

REMOVING THE FLYWHEEL AND

STATOR COIL ASSEMBLY ................. 3-16

CHECKING THE FLYWHEEL AND

STATOR COIL ASSEMBLY ................. 3-17

INSTALLING THE FLYWHEEL AND

STATOR COIL ASSEMBLY ................. 3-17

INSTALLING THE CRANKSHAFT

POSITION SENSOR........................... 3-19

CYLINDER HEAD COVERS, CYLINDER

HEADS......................................................3-20

CYLINDER HEAD #1 ..........................3-20

CYLINDER HEAD #2 ..........................3-22

CHECKING THE ROCKER ARMS

AND ROCKER ARM SHAFTS.............3-24

CHECKING THE PUSH RODS ...........3-24

REMOVING THE CYLINDER

HEADS ................................................3-24

CHECKING THE CYLINDER

HEADS ................................................3-24

INSTALLING THE CYLINDER HEAD

ASSEMBLY..........................................3-25

VALVES ....................................................3-27

REMOVING THE VALVES AND

VALVE SPRINGS.................................3-28

CHECKING THE VALVES AND

VALVE SPRINGS.................................3-28

CHECKING THE VALVE SEATS .........3-30

VALVE LAPPING .................................3-31

INSTALLING THE VALVES AND

VALVE SPRINGS.................................3-32

OIL PUMP.................................................3-33

DISASSEMBLING THE OIL PUMP.....3-34

CHECKING THE OIL PUMP ...............3-34

CHECKING THE RELIEF VALVE........3-35

CHECKING THE CRANKCASE

COVER 2.............................................3-35

INSTALLING THE OIL PRESSURE

SWITCH ..............................................3-35

ASSEMBLING THE OIL PUMP...........3-36

INSTALLING THE CRANKCASE

COVER 2.............................................3-37

PISTONS, CAMSHAFT, CRANKCASE,

AND CRANKSHAFT ................................3-38

CRANKCASE ......................................3-38

PISTONS, CAMSHAFT, AND

CRANKSHAFT ....................................3-40

REMOVING THE FLYWEIGHT

SHAFT ASSEMBLY AND

GOVERNOR FORK.............................3-41

DISASSEMBLING THE FLYWEIGHT

SHAFT ASSEMBLY.............................3-41

CHECKING THE FLYWEIGHT

SHAFT ASSEMBLY.............................3-41

ASSEMBLING THE FLYWEIGHT

SHAFT ASSEMBLY.............................3-42

INSTALLING THE FLYWEIGHT

SHAFT ASSEMBLY AND

GOVERNOR FORK ............................ 3-42

REMOVING THE CAMSHAFT AND

VALVE LIFTERS ................................. 3-43

CHECKING THE CAMSHAFT ............ 3-43

CHECKING THE VALVE LIFTERS ..... 3-44

CHECKING THE REED VALVE.......... 3-45

INSTALLING THE VALVE LIFTERS

AND CAMSHAFT................................ 3-45

INSTALLING THE COVER 1............... 3-45

INSTALLING THE COVER 2............... 3-46

CHECKING THE CRANKCASE

COVER 1 ............................................ 3-46

INSTALLING THE CRANKCASE

COVER 1 ............................................ 3-47

CHECKING THE CYLINDERS AND

PISTONS ............................................ 3-47

CHECKING THE CRANKCASE.......... 3-49

CHECKING THE PISTON PINS ......... 3-49

CHECKING THE PISTON RINGS ...... 3-49

CHECKING THE CRANKSHAFT........ 3-51

CHECKING THE CONNECTING

RODS OIL CLEARANCE.................... 3-52

INSTALLING THE PISTONS AND

PISTON RINGS .................................. 3-52

INSTALLING THE CRANKSHAFT...... 3-54

FUEL

FUEL PUMPS ............................................ 4-1

REMOVING THE HIGH-PRESSURE

FUEL PUMP.......................................... 4-2

CHECKING THE LOW-PRESSURE

FUEL PUMP.......................................... 4-3

CHECKING THE HIGH-PRESSURE

FUEL PUMP.......................................... 4-3

INSTALLING THE HIGH-PRESSURE

FUEL PUMP.......................................... 4-4

THROTTLE BODY ASSEMBLY................. 4-6

REMOVING THE THROTTLE BODY

ASSEMBLY ........................................... 4-7

CHECKING THE THROTTLE BODY

ASSEMBLY ........................................... 4-7

INSTALLING THE THROTTLE BODY

ASSEMBLY ........................................... 4-7

FUEL INJECTORS AND INTAKE

MANIFOLD .................................................4-9

REMOVING THE FUEL

INJECTORS ........................................4-11

INSTALLING THE FUEL

INJECTORS ........................................4-12

REMOVING THE MANIFOLD

ABSOLUTE PRESSURE SENSOR ....4-14

INSTALLING THE MANIFOLD

ABSOLUTE PRESSURE SENSOR ....4-14

REMOVING THE INTAKE

MANIFOLD ..........................................4-14

CHECKING THE INTAKE

MANIFOLD ..........................................4-15

INSTALLING THE INTAKE

MANIFOLD ..........................................4-15

ELECTRICAL

CIRCUIT DIAGRAM....................................5-1

FUEL INJECTION SYSTEM.......................5-3

FI DIAG TOOL INSTRUCTIONS ...........5-3

FUEL INJECTION DIAGRAM................5-9

ERROR CODE LIST............................5-10

DIAG CODE LIST................................5-11

FUEL INJECTION SYSTEM

TROUBLESHOOTING.........................5-12

ELECTRICAL COMPONENTS.................5-25

CHECKING THE SWITCH

CONTINUITY.......................................5-27

CHECKING THE FUSES ....................5-27

CHECKING THE OIL PRESSURE

SWITCH ..............................................5-28

CHECKING MANIFOLD ABSOLUTE

PRESSURE SENSOR.........................5-29

CHECKING THE THROTTLE

POSITION SENSOR ...........................5-29

CHECKING THE CRANKSHAFT

POSITION SENSOR ...........................5-30

CHECKING THE ENGINE

TEMPERATURE SENSOR..................5-31

CHECKING THE IGNITION COILS.....5-32

CHECKING THE IGNITION SPARK

GAP.....................................................5-33

CHECKING THE SPARK PLUG

CAPS...................................................5-33

CHECKING THE STATOR COIL

ASSEMBLY ......................................... 5-34

CHECKING THE RECTIFIER/

REGULATOR ...................................... 5-35

CHECKING THE FUEL

INJECTORS........................................ 5-35

CHECKING THE STARTER MOTOR

OPERATION ....................................... 5-36

ELECTRIC STARTING SYSTEM............. 5-37

REMOVING THE STARTER

MOTOR............................................... 5-37

DISASSEMBLING THE STARTER

MOTOR............................................... 5-38

CHECKING THE ARMATURE COIL... 5-39

CHECKING THE BRUSH ................... 5-40

CHECKING THE STARTER RELAY ... 5-40

ASSEMBLING THE STARTER

MOTOR............................................... 5-40

TROUBLESHOOTING

ENGINE DOES NOT START...................... 6-1

IGNITION SYSTEM .............................. 6-1

ELECTRIC STARTING SYSTEM ......... 6-2

FUEL INJECTION SYSTEM ................. 6-2

FUEL PUMP SYSTEM.......................... 6-2

OTHER TROUBLES................................... 6-3

ENGINE STARTS BUT STALLS............ 6-3

ENGINE SPEED DOES NOT

INCREASE............................................ 6-4

ENGINE SPEED IS UNEVEN............... 6-5

THE BATTERY IS NOT CHARGED ...... 6-5

GOVERNOR OPERATION.................... 6-6

OIL PRESSURE SYSTEM ......................... 6-6

SPECIFICATIONS

GENERAL SPECIFICATIONS ................... 7-1

MAINTENANCE SPECIFICATIONS .......... 7-3

ENGINE ................................................ 7-3

ELECTRICAL........................................ 7-7

TIGHTENING TORQUES........................... 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

LEFT SIDE VIEW ................................7-16

RIGHT SIDE VIEW..............................7-18

REAR SIDE VIEW...............................7-22

1

2

3

4

5

6

7

8

9

10

GENERAL INFORMATION

1-1

GENERAL INFORMATION

MACHINE IDENTIFICATION

SERIAL NUMBER

The serial number is printed on the label “1” affixed to the

position 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

:

1

Model

Code

Starting serial num-

ber

MX775VJ7L6

7U2J

7U2J-1000101-

MX775VJ7W6

7U2J-2000101-

MX775VJ7X6

7U2J-3000101-

MX800VJ7L6

7U1J

7U1J-1000101-

MX800VJ7W6

7U1J-2000101-

MX800VJ7X6

7U1J-3000101-

MX825VJ7L6

7UDJ

7UDJ-1000101-

MX825VJ7W6

7UDJ-2000101-

MX825VJ7X6

7UDJ-3000101-

DIMENSIONS

1-2

1

2

3

4

5

6

7

8

9

10

GENERAL INFORMATION

DIMENSIONS

TOP

MOUNTING BASE

*1: UNC: Unified coarse thread (Unit: in)

*2: PCD: Pitch Circle Diameter

mm (in)

mm (in)

157.1(6.19)

499.2(19.65）

35°

35°

45°

45°

PCD 254

4 3/8-16UNC

1-3

1

2

3

4

5

6

7

8

9

10

GENERAL INFORMATION

DIMENSIONS

REAR

REAR (For models equipped with a muffler)

mm (in)

mm (in)

463.8(18.26)

231.1(9.1)

463.8(18.26)

445.4(17.54)

231.1(9.1)