🏷️ Basic Information

Make:

Yamaha

Model:

YZ125

Model Variant:

Motocross

Engine Code:

Likely 1TX variant (specific code may vary by region/VIN)

Chassis Code:

Likely 5NY or 5XC (specific code may vary by region/VIN)

Generation:

Third Generation (2002-2005) leading into updated 2006 model, often considered part of the broader '03-'07 era updates.

👋 Introduction

Segment:

Performance Motocross Competition Motorcycle

Target Audience:

Motocross racers, off-road enthusiasts, mechanics, and owners seeking in-depth maintenance and repair knowledge.

Competitors:

KTM 125 SX, Honda CR125R, Suzuki RM125, Kawasaki KX125.

Yz125 Features 2006:

Updated suspension (e.g., KYB SSS forks), potent two-stroke engine, lightweight chassis, strong braking system.

Manual Value Proposition:

Provides essential technical data, repair procedures, and diagnostic information to maintain and repair the YZ125, reducing reliance on specialized shops and enhancing vehicle longevity.

📋 Manual Details

Coverage Regions:

France (FR), Germany (GER), Italy (ITA)

Page Count:

Estimated 300-500 pages (typical for comprehensive workshop manuals for this era)

Manual Type:

Workshop Service Repair Manual

Language:

English (primary, based on general availability for these manuals), Italian, French, German

Format:

Digital Download (PDF)

📖 Manual Coverage

Engine Systems:

Engine disassembly, assembly, inspection, troubleshooting, tuning, carburetor overhaul, cooling system, lubrication.

Transmission Systems:

Clutch service, gearbox disassembly and reassembly, shift mechanism, transmission fluid.

Chassis Suspension:

Front fork (KYB SSS type or similar), rear shock absorber (Monoshock), linkage, bearings, steering system.

Brakes:

Front and rear brake systems (hydraulic disc), caliper service, master cylinder overhaul, brake fluid, bleeding procedures.

Electrical System:

Ignition system, lighting, wiring diagrams, troubleshooting electrical faults, battery.

Fuel System:

Carburetor (Mikuni VM38 or similar), fuel lines, fuel tank, fuel pump (if applicable).

Exhaust System:

Exhaust pipe, silencer, power valve system maintenance.

Cooling System:

Radiator, hoses, coolant, thermostat (if applicable).

Basic Maintenance:

Oil changes, filter replacements, chain adjustment, spark plug service, air filter cleaning/replacement, pre-ride inspections.

Engine Repair:

Top-end rebuild (piston, rings, cylinder), bottom-end overhaul (crankshaft, bearings, seals), valve adjustments (if applicable), power valve cleaning and adjustment.

Transmission Repair:

Gearbox disassembly, inspection of gears and shift drum, clutch plate replacement, bearing replacement.

Suspension Service:

Front fork oil change, seal replacement, fork leg disassembly, rear shock absorber service, linkage bearing maintenance.

Brake Overhaul:

Brake pad replacement, caliper piston service, master cylinder rebuilding, brake fluid flush and bleed.

Electrical Troubleshooting:

Diagnosing ignition issues, testing stator and coil, wiring fault finding using diagrams.

Carburetor Tuning:

Jetting recommendations, adjustment procedures for altitude and conditions, float height adjustment.

Troubleshooting Guides:

Common problems and their diagnostic steps, symptom-based troubleshooting.

Depth:

Comprehensive (includes detailed disassembly, assembly, and specifications for major component overhauls).

Diagnostic Capabilities:

Advanced diagnostics for engine performance, ignition timing, and electrical systems.

Rebuild Procedures:

Detailed step-by-step instructions for complete engine and gearbox rebuilds.

📊 Manual Specifications

File Type:

PDF

Searchability:

Likely text-searchable (if digitally produced from original source).

Image Resolution:

High resolution for clear diagrams and photos.

Diagram Clarity:

Clear, detailed exploded views and schematics.

Binding:

N/A (Digital Download)

Paper:

N/A (Digital Download)

⚙️ Engine Specifications

Engine Type:

2-Stroke, Single Cylinder

Displacement:

124 cc (7.57 cu. in.)

Bore X Stroke:

54.0 mm x 54.5 mm (2.126 in x 2.146 in)

Compression Ratio:

Approximately 9.7:1 to 10.5:1 (dependent on specific configuration, consult manual for exact)

Cooling System:

Liquid-cooled

Power Valve System:

Yamaha Power Valve System (YPVS)

Horsepower:

Estimated 35-40 HP (peak, actual figures vary and are not typically published by Yamaha for competition models in manuals).

Torque:

Not officially published, but optimized for mid-range power delivery.

Carburetor:

Mikuni VM38 (38mm) flat-slide carburetor

Fuel Type:

Unleaded gasoline (91 octane or higher recommended)

Fuel Mixture:

Pre-mix (Gasoline/2-stroke oil) - Refer to manual for specific oil ratio (typically 20:1 or 32:1).

2 Stroke Oil Type:

High-quality 2-stroke engine oil specifically formulated for racing motorcycles. Refer to manual for specific recommendations (e.g., Yamalube).

Piston Type:

Single-ring, lightweight piston

🔧 Transmission

Transmission Type:

Constant mesh 6-speed

Clutch Type:

Wet, multi-plate

Gear Ratios:

Specific ratios detailed in manual (e.g., 1st: 2.667, 2nd: 1.778, 3rd: 1.333, 4th: 1.091, 5th: 0.958, 6th: 0.870).

Final Drive:

Chain drive

Transmission Oil Type:

API GL-4, SAE 10W-30 or 20W-40 motorcycle gear oil. Consult manual for precise specification and capacity.

📐 Dimensions

Length:

Approx. 2185 mm (86.0 in)

Width:

Approx. 825 mm (32.5 in)

Height:

Approx. 1280 mm (50.4 in)

Wheelbase:

Approx. 1480 mm (58.3 in)

Ground Clearance:

Approx. 355 mm (14.0 in)

Dry Weight:

Approx. 93 kg (205 lbs)

Wet Weight:

Not officially specified, but includes all fluids and ready-to-ride weight.

Fuel Tank Capacity:

7.2 Liters (1.9 US gal)

Front Tire Size:

80/100-21 51M

Rear Tire Size:

110/90-19 62M

Front Wheel:

21-inch

Rear Wheel:

19-inch

🛡️ Safety Features

Safety Certification:

Not applicable for competition off-road vehicles (designed for closed course use).

Braking System:

Hydraulic disc brakes front and rear for superior stopping power and modulation.

Suspension Performance:

Advanced suspension systems (e.g., KYB SSS front forks) designed for control and stability over varied terrain.

Chassis Design:

Lightweight and rigid aluminum frame for predictable handling and rider feedback.

💡 Technology Features

Infotainment System:

Not applicable (competition off-road motorcycle).

Assistance Features:

None (competition off-road motorcycle).

Connectivity Features:

None (competition off-road motorcycle).

Engine Management:

Mechanical carburetor with Yamaha Power Valve System (YPVS) for optimized power band.

🔧 Maintenance

Oil Change Interval:

Every 10-15 hours of riding or as per manual recommendations for track use.

Air Filter Cleaning:

After every few rides or as needed based on dust conditions.

Spark Plug Service:

Inspect every 20-30 hours, replace as needed.

Top End Rebuild:

Recommended every 40-60 hours of hard use (piston, rings, cylinder inspection/replacement).

Suspension Service:

Fork oil change every 20-30 hours, seal replacement as needed. Rear shock service as per manual recommendations.

Coolant:

50% Ethylene Glycol based coolant and 50% distilled water. Refer to manual for exact capacity.

Brake Fluid:

DOT 4 hydraulic brake fluid.

Chain Lube:

High-quality motorcycle chain lubricant.

Power Valve Sticking:

Carbon buildup can cause the YPVS to stick, affecting power delivery. Regular cleaning is recommended.

Clutch Wear:

Aggressive riding can lead to premature clutch plate wear. Regular adjustment and inspection are necessary.

Suspension Seals:

Fork and shock seals can degrade over time, leading to leaks. Regular maintenance and seal replacement are crucial.

Carburetor Fouling:

Incorrect jetting or fuel quality can lead to carburetor fouling or poor performance. Proper tuning is essential.

📚 Vehicle History

Brand Focus:

Yamaha Corporation is a Japanese multinational corporation and one of the world's largest manufacturers of musical instruments. Yamaha Motor Company, established in 1955, is a separate entity focused on motorcycles, marine products, and other motorized vehicles.

Yz Series Heritage:

The YZ series has a long and successful history in motocross racing, dating back to the early 1970s. The YZ125 has been a staple in the 125cc class, known for its potent engines and competitive performance.

Yz125 2006 Updates:

The 2006 model year saw significant updates, building on the successful 2005 platform, often including refined suspension settings, chassis geometry tweaks, and engine performance improvements, particularly noted for the introduction/enhancement of advanced fork technology like KYB SSS.

Production Location:

Typically manufactured in Japan by Yamaha Motor Company.

🏆 Awards & Recognition

Motocross Class Performance:

The YZ125 has historically been a highly competitive machine in its class, often praised for its agile handling and potent engine, making it a favorite among amateur and professional racers.