Yamaha DT125 DT125R 1987 1988 Workshop Service Repair Manual

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Type: Motorcycle

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Sku: 50992

Tags: 1987 1988 DT125 DT125R Misc Motorcycle Motorcycles Yamaha

Product variants

Description

The DT125 and DT125R, produced for the 1987 and 1988 model years, represent a lineage of reliable and capable lightweight dual-sport motorcycles. Known for their robust two-stroke, single-cylinder engines and strong off-road prowess, these models offered a versatile riding experience suitable for both trails and general use. With a focus on durability and straightforward engineering, the DT series has a well-earned reputation for providing dependable performance, making it a popular choice for riders seeking adventure and accessibility. This comprehensive workshop service repair manual provides detailed guidance for the maintenance and repair of the DT125 / DT125R. It covers a wide array of systems, including complete engine overhauls, fuel and transmission systems, chassis and suspension components, braking, and the electrical system. The manual includes step-by-step procedures for routine maintenance, engine rebuilds, carburetor tuning, and troubleshooting, offering in-depth technical specifications and wiring diagrams. This resource is designed to assist owners, mechanics, and technicians in preserving the longevity and optimal performance of their vehicles.

🏷️ Basic Information

Identification

Make:

Yamaha

Model:

DT125 / DT125R

Years Covered:

1987, 1988

Codes

Engine Code Indicator:

DT125, DT125R

👋 Introduction

Market Position

Vehicle Segment:

Lightweight Dual-Sport / Enduro Motorcycle

Competitive Analysis

Key Competitors Era:

Honda CR125R, Kawasaki KX125, Suzuki RM125 (motocross variants); various enduro machines.

Key Features

Dt125R Reputation:

Known for its reliability, off-road capability, and relatively simple yet effective two-stroke engine.

Manual Utility

Value Proposition:

Essential resource for owners and mechanics to maintain and repair the DT125/DT125R, ensuring longevity and optimal performance.

📋 Manual Details

Coverage Areas

Manual Scope:

Workshop Service Repair

Page Count

Estimated Pages:

Hundreds (as per description)

Manual Type

Manual Classification:

Factory Official Full Service Repair Manual

Language

Primary Language:

English

Format

Delivery Format:

PDF Download

📖 Manual Coverage

Systems Covered

Engine System:

Complete overhaul, diagnostics, tuning, lubrication, cooling, exhaust.

Fuel System:

Carburetor identification, adjustment, cleaning, fuel tank, fuel lines, petcock.

Transmission System:

Gearbox operation, clutch, shift mechanism, lubrication, repair procedures.

Chassis Frame:

Frame inspection, alignment, swingarm, pivot bearings, steering head bearings.

Suspension Front:

Front fork disassembly, assembly, oil change, seal replacement, spring rates.

Brakes Front:

Disc brake caliper servicing, hydraulic lines, master cylinder, pad replacement, bleeding.

Electrical System:

Ignition system, lighting, charging system (stator, regulator/rectifier), battery, wiring diagrams.

Cooling System:

Air cooling (fins), component checks.

Exhaust System:

Muffler, pipe inspection, sealing.

Wheels Tires:

Wheel bearing maintenance, spoke tensioning, tire pressure specifications.

Bodywork Plastics:

Fairing, fenders, seat, fuel tank removal and installation.

Suspension Rear

Rear Shock ABSorber:

Monoshock unit service, linkage maintenance, damping adjustments.

Brakes Rear

Rear Brake System:

Drum brake inspection, adjustment, shoe replacement.

Procedures Included

Routine Maintenance:

Oil changes, filter replacements, chain adjustment, spark plug checks, air filter cleaning.

Engine Rebuild:

Top-end overhaul, piston, rings, cylinder, crankshaft service.

Carburetor Tuning:

Jetting, idle speed, mixture adjustments for optimal performance.

Troubleshooting Diagnostics:

Systematic fault finding for common and complex issues.

Wiring Diagrams:

Detailed electrical schematics for accurate diagnosis and repair.

Component Disassembly Assembly:

Step-by-step guides for all major motorcycle components.

Technical Depth

Diagnostic Capability:

Advanced diagnostics and troubleshooting for intricate issues.

Repair Complexity:

Covers everything from basic adjustments to complete engine and chassis overhauls.

Completeness:

Full factory specification for comprehensive repair and maintenance.

📊 Manual Specifications

File Format

Document Format:

Print Quality

Digital Resolution:

High resolution, suitable for printing.

Binding Type

Digital Print Option:

Printable in its entirety or specific sections.

Paper Type

Digital Paper Equivalent:

N/A (Digital File)

⚙️ Engine Specifications

Primary Engine

Engine Type:

Two-Stroke, Single-Cylinder

Displacement:

123 cc (7.5 cubic inches)

Bore X Stroke:

56.4 mm x 50.0 mm (approximate)

Compression Ratio:

Approx. 7.2:1 (varies slightly by model revision)

Cooling System:

Forced Air Cooling

Ignition System:

CDI (Capacitor Discharge Ignition)

Spark Plug Type:

NGK B8ES (or equivalent, consult manual for specific)

Performance

Horsepower Estimated:

Approx. 17-20 HP (at crankshaft, varies by market and tuning)

Torque Estimated:

Approx. 14-16 Nm (at crankshaft, varies by market and tuning)

Fuel System

Carburetor Model:

Mikuni VM26SS (typical for this era)

Fuel Type:

Unleaded Gasoline (min. 91 RON / 87 AKI recommended)

Oil Mixture Ratio:

50:1 (2-stroke oil to gasoline in the oil injection system)

🔧 Transmission

Standard

Transmission Type:

6-Speed Constant Mesh

Features

Clutch Type:

Wet, Multi-Plate

Final Drive:

Chain Drive (O-ring sealed type typical)

📐 Dimensions

Exterior

Overall Length:

Varies by specific model variant, consult manual for exact figures.

Weights

Dry Weight Estimated:

Approx. 100-110 kg (220-242 lbs)

Fuel Tank Capacity:

Approx. 9.5 - 10.5 Liters (2.5 - 2.8 Gallons)

🛡️ Safety Features

Ratings

Crash Safety Standards:

N/A (Motorcycle, not subjected to automotive crash ratings)

Active Features

Braking System:

Front Disc Brake, Rear Drum Brake for effective stopping power.

Passive Features

Frame Construction:

Steel Frame providing structural integrity.

💡 Technology Features

Infotainment

Instrument Cluster:

Analog speedometer, tachometer, and basic indicator lights (neutral, turn signals, high beam).

Driver Assistance

ABS Availability:

Not equipped with ABS.

Connectivity

Connectivity Features:

N/A (No modern electronic connectivity features).

🔧 Maintenance

Service Intervals

Engine Oil Change:

Refer to manual; typically every 2,000-3,000 km or annually. Crankcase oil change is crucial.

Air Filter Cleaning:

Check and clean every 1,000-2,000 km, especially in dusty conditions.

Chain Lubrication Adjustment:

Lubricate every 500 km, adjust tension as needed according to manual specifications.

Spark Plug Service:

Inspect and clean/gap every 3,000-4,000 km, replace as necessary.

Fluid Specifications

Transmission Oil Type:

Yamaha Gear Oil 10W-30 (or equivalent API GL-4 specification)

Fork Oil Type:

Yamaha Fork Oil G10 (or equivalent SAE 10W)

Brake Fluid Type:

DOT 3 or DOT 4 Hydraulic Brake Fluid

Known Issues

Common Wear Items:

Piston rings, crankshaft seals, clutch plates, and suspension seals are common wear items on high-mileage units.

Carburetor Performance:

Carburetors can be sensitive to altitude and air filter condition; regular cleaning and tuning are beneficial.

Electrical Reliability:

Older wiring harnesses can develop corrosion or damage, affecting ignition or charging systems. Manual is key for troubleshooting.

📚 Vehicle History

Brand Heritage

Yamaha Motorcycle Legacy:

Yamaha has a long history of producing reliable and performance-oriented motorcycles, particularly in the off-road and dual-sport categories.

Model Evolution

Dt Series Development:

The DT series originated in the late 1960s and evolved through various displacements and configurations, emphasizing versatility and durability.

Production

Manufacturing Location Typical:

Japan (primary manufacturing hub for Yamaha at this time)

Production Years Model

Dt125R Production Span:

Covered years 1987-1988, part of a continuous DT125 lineage.

🏆 Awards & Recognition

Recognitions

Model Reputation:

Praised for its robustness and ability to handle diverse terrain, a popular choice for adventure and trail riding.

Ratings

Consumer Ratings Historical:

Generally well-regarded for reliability and ease of maintenance by owners of the era.