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Yamaha YZ125X 2021 User Manual

Yamaha YZ125X 2021
268 pages
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Read this manual carefully before operating this vehicle.
2021
OWNER’S SERVICE MANUAL
YZ125X
YZ125XM
LIT-11626-34-08 B1B-2819U-10

Table of Contents

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Yamaha YZ125X 2021 Specifications

General IconGeneral
Displacement125cc
Bore x Stroke54.0mm x 54.5mm
IgnitionCDI
TransmissionConstant-mesh 6-speed; multiplate wet clutch
Final DriveChain
Suspension FrontKYB® Speed-Sensitive System inverted fork; fully adjustable, 11.8-in travel
Brakes FrontHydraulic disc, 270mm
Brakes RearHydraulic disc, 245mm
Tires Front80/100-21
Seat Height38.2 in
Wheelbase58.3 in
Fuel Capacity2.1 gal
Engine TypeLiquid-cooled 2-stroke; reed-valve inducted
Fuel DeliveryKeihin PWK38S carburetor
Suspension RearKYB® single shock; 12.4-in travel
Tires Rear110/100-18
L x W x H32.5 in

Summary

YAMAHA YZ MOTORCYCLE LIMITED WARRANTY

HOW TO USE THIS MANUAL

SYMBOLS

Explains symbols used in the manual for easier understanding.

GENERAL INFORMATION

SAFETY INFORMATION

Provides essential safety guidelines for operating and maintaining the motorcycle.

DESCRIPTION

Details the various parts and components of the motorcycle.

IMPORTANT INFORMATION

Covers crucial details for preparation, parts, and procedures before servicing.

SPECIAL TOOLS

Lists specialized tools required for accurate adjustment and assembly.

STARTING AND BREAK-IN

Provides instructions for starting the engine and the break-in procedure.

MAINTENANCE AFTER BREAK-IN

MAJOR MAINTENANCE

Details the comprehensive maintenance required after the break-in period.

TORQUE-CHECK POINTS

ENGINE TIGHTENING TORQUES

Lists specific torque values for engine components and fasteners.

SPECIFICATIONS

GENERAL SPECIFICATIONS

Outlines general dimensions, weight, and capacity of the vehicle.

ENGINE SPECIFICATIONS

Details technical specifications related to the engine, including bore, stroke, and clearances.

CHASSIS SPECIFICATIONS

Lists technical specifications for the chassis, suspension, and brakes.

ELECTRICAL SPECIFICATIONS

Provides detailed specifications for the motorcycle's electrical system components.

PERIODIC CHECKS AND ADJUSTMENTS

MAINTENANCE INTERVALS

Outlines recommended maintenance schedules based on usage intervals or mileage.

PRE-OPERATION INSPECTION AND MAINTENANCE

Details essential checks and maintenance to perform before operating the motorcycle.

ENGINE

Covers checks and adjustments related to the engine's operation and components.

CHASSIS

Details checks and adjustments for the motorcycle's chassis, brakes, and suspension.

CHASSIS

FRONT WHEEL

Details procedures for removing, disassembling, checking, assembling, and installing the front wheel.

REAR WHEEL

Details procedures for removing, checking, and installing the rear wheel and sprocket.

FRONT BRAKE

Covers removal, disassembly, checking, assembly, and installation of the front brake system.

HANDLEBAR

Details procedures for removing, checking, and installing the handlebar and its controls.

FRONT FORK

Covers removal, disassembly, checking, assembly, and installation of the front fork legs.

CHAIN DRIVE

Covers procedures for removing, checking, and installing the drive chain and sprockets.

ENGINE

ENGINE REMOVAL

Provides instructions for removing the engine, including the exhaust pipe.

CLUTCH

Details procedures for removing, checking, and installing the clutch assembly.

CRANKCASE

Details procedures for separating, disassembling, checking, and assembling the crankcase.

COOLING SYSTEM

RADIATOR

Covers procedures for removing and checking the radiator.

WATER PUMP

Details procedures for removing, disassembling, checking, and assembling the water pump.

FUEL SYSTEM

FUEL TANK

Covers procedures for removing the fuel tank and its components.

AIR FILTER

Details procedures for removing and maintaining the air filter element.

CARBURETOR

Covers removal, disassembly, checking, assembly, and installation of the carburetor.

ELECTRICAL SYSTEM

IGNITION SYSTEM

Covers troubleshooting and checking components of the ignition system.

ELECTRICAL COMPONENTS

Identifies and illustrates key electrical components of the motorcycle.

TROUBLESHOOTING

GENERAL INFORMATION

Provides general guidance and context for the troubleshooting information.

TROUBLESHOOTING OF ENGINE

Addresses common engine starting and running issues and their causes.

TROUBLESHOOTING OF CLUTCH

Covers common clutch problems like slippage and dragging, with possible causes and actions.

TROUBLESHOOTING OF TRANSMISSION

Addresses issues related to shifting gears, gears jumping out, and transmission noise.

TROUBLESHOOTING OF COOLING SYSTEM

Covers overheating and noise issues related to the cooling system.

TROUBLESHOOTING OF BRAKE

Addresses poor disc brake performance, fluid leaks, and stuck components.

TROUBLESHOOTING OF SUSPENSION

Covers front and rear suspension issues like stiffness, softness, and leaks.

TROUBLESHOOTING OF STEERING/HANDLING

Addresses handlebar wobble and heavy steering issues.

TUNING

ENGINE (CARBURETOR SETTING)

Explains how to adjust carburetor settings for optimal engine performance based on conditions.

CHASSIS (SUSPENSION SETTING)

Discusses tuning aspects of the chassis, including sprockets, tire pressure, and suspension.

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