🏷️ Basic Information

Make:

Yamaha

Model:

YZ125

Model Variant:

YZ125X/X1

Year Primary Coverage:

2008

Year Secondary Coverage:

2009, 2010, 2011, 2012

Chassis Code Typical:

This manual focuses on the YZ125 chassis and its specific components, which typically have a unique VIN identifier.

Engine Code Typical:

YZ125 engines will have a specific code denoting displacement and variant, detailed within the manual.

👋 Introduction

Segment:

Motocross/Off-Road Competition

Target Audience:

Motocross racers, off-road enthusiasts, mechanics specializing in dirt bikes.

Key Competitors Model Year:

KTM 125 SX, Honda CR125R, Suzuki RM125, Kawasaki KX125 (during this era).

Yz125 Reputation:

Renowned for its lightweight chassis, tractable power delivery, and ease of handling, making it a popular choice for riders transitioning to the 125cc class or seeking a nimble, competitive machine.

Manual Value Proposition:

Provides in-depth technical information essential for maintaining peak performance, ensuring longevity, and executing repairs on the Yamaha YZ125, saving owners significant time and money compared to relying solely on guesswork or dealer service.

📋 Manual Details

Primary Coverage:

Yamaha YZ125 (2008 Model Year), YZ125X/X1 Variants

Extended Coverage:

Compatible with similar components and procedures for 2009, 2010, 2011, and 2012 Yamaha YZ125 models.

Estimated Pages:

Approximately 300-500 pages (typical for a comprehensive service manual)

Type:

Service Repair Workshop Manual

Language:

English

Format:

Digital (likely PDF), printable pages, searchable text

📖 Manual Coverage

Engine:

Full engine teardown, assembly, tuning, troubleshooting, specifications, power valve system, cooling system (if applicable, though YZ125 is typically air-cooled).

Transmission:

Clutch operation and adjustment, gearbox disassembly and assembly, gear ratios, lubrication, troubleshooting.

Suspension:

Front fork (KYB Speed Sensitive System or similar) disassembly, assembly, oil levels, pressure adjustments, rear shock absorber overhaul, spring rates, damping adjustments.

Brakes:

Front and rear brake system inspection, caliper overhaul, master cylinder service, pad replacement, bleeding procedures, rotor specifications.

Electrical System:

Ignition system, CDI unit, stator, flywheel, wiring diagrams, lighting (if applicable), battery maintenance (if electric start is present, which is rare for YZ125).

Fuel System:

Carburetor (Mikuni VM34 or similar) disassembly, cleaning, jetting, float adjustment, fuel tank, fuel lines, petcock.

Chassis And Frame:

Frame inspection, steering head bearing service, swingarm maintenance, linkage lubrication, wheel bearing replacement, sprocket and chain maintenance.

Exhaust System:

Exhaust pipe and silencer inspection, packing replacement (for silencer), mounting hardware.

Routine Maintenance:

Oil changes, filter cleaning/replacement, chain adjustment, tire pressure checks, general inspection, spark plug replacement.

Scheduled Maintenance:

Detailed service intervals for engine rebuilds, suspension servicing, clutch wear checks, and other critical components.

Disassembly Assembly:

Step-by-step instructions for complete teardown and reassembly of major components and systems.

Troubleshooting:

Diagnostic procedures for common problems, including starting issues, poor performance, and component failures.

Rebuild Procedures:

Comprehensive guidance for engine top-end and bottom-end rebuilds, carburetor rebuilding, and suspension overhauls.

Adjustment Procedures:

Detailed instructions for clutch lever free play, throttle cable slack, brake lever adjustment, and suspension settings.

Depth:

Comprehensive, suitable for professional mechanics and experienced DIY enthusiasts. Covers everything from basic checks to full engine rebuilds and advanced diagnostics.

📊 Manual Specifications

File Type:

PDF

Searchability:

Yes, text is selectable and searchable.

Print Readability:

High resolution, suitable for printing individual pages or the entire manual.

Binding Format:

Digital, typically distributed as a single downloadable file.

Recommended Paper:

Standard printer paper (8.5" x 11" or A4) for printing.

⚙️ Engine Specifications

Engine Type:

2-Stroke, Liquid-Cooled, Reed Valve

Displacement:

125cc

Bore X Stroke:

54.0 x 54.5 mm

Compression Ratio:

9.9:1 (typical, specific value in manual)

Intake System:

Reed valve, YPVS (Yamaha Power Valve System)

Horsepower Approx:

35-40 HP (peak, varies with tuning)

Torque Approx:

17-19 lb-ft (peak, varies with tuning)

Carburetor Model:

Mikuni TM38 (typically)

Fuel Type:

Unleaded gasoline (91 octane or higher recommended)

Fuel Mixture:

Premix 2-stroke oil to gasoline (typically 50:1 or 40:1, refer to manual for precise ratio and oil type).

Coolant Type:

High-quality ethylene glycol-based antifreeze (refer to manual for specific type and ratio).

Transmission Oil Type:

Yamalube 2R or equivalent high-quality 2-stroke premix oil (for fuel/oil injection if applicable, otherwise engine oil for gearbox).

🔧 Transmission

Transmission Type:

5-speed constant mesh

Clutch Type:

Wet, multi-plate

Gear Ratios:

Detailed ratios for each gear (1st through 5th) provided in the manual.

Final Drive:

Chain drive (sprocket sizes and chain pitch specified in manual).

📐 Dimensions

Overall Length:

Approximately 2140 mm (refer to manual for exact measurement)

Overall Width:

Approximately 825 mm (refer to manual for exact measurement)

Overall Height:

Approximately 1280 mm (refer to manual for exact measurement)

Dry Weight:

Approximately 91 kg (refer to manual for exact measurement)

Fuel Tank Capacity:

7.0 Liters (1.85 Gallons)

Front Suspension Travel:

295 mm (11.6 inches)

Rear Suspension Travel:

310 mm (12.2 inches)

🛡️ Safety Features

Safety Certification:

Not applicable for off-road competition motorcycles in typical automotive safety rating systems (e.g., NHTSA, Euro NCAP).

Active Safety Features:

Performance-oriented chassis and suspension for optimal handling and rider control in off-road conditions. Effective braking system for stopping power.

Passive Safety Features:

Sturdy frame construction designed to withstand the rigors of off-road riding. Rider protection is primarily dependent on personal protective equipment (PPE) as detailed in owner's manuals.

💡 Technology Features

Infotainment Features:

Not applicable to this off-road competition motorcycle model.

Driver Assistance Features:

Not applicable. Rider skill and judgment are the primary control systems.

Connectivity Features:

Not applicable. No electronic connectivity features present on this model.

🔧 Maintenance

Engine Top End Rebuild:

Recommended every 30-50 hours of racing or equivalent hard use (specific guidance in manual).

Piston Ring Replacement:

Often recommended concurrently with top-end rebuilds or based on compression testing.

Clutch Inspection:

Regularly, with specific mileage/hour recommendations for plate wear and spring checks.

Suspension Service:

Annual service or every 50-100 hours of use for fork and shock seals and oil.

Air Filter Cleaning:

After every ride or more frequently in dusty conditions.

Fork Oil Type Capacity:

Specific viscosity and fill level for KYB forks (e.g., SAE 0W-20 or similar, precise volume detailed in manual).

Rear Shock Oil:

Specific type and quantity for the rear shock absorber (manual will specify).

Typical Yz125 Wear Items:

Clutch plates, piston rings, exhaust packing, wheel bearings, steering head bearings, and suspension seals are common wear items requiring regular inspection and replacement.

Carburetor Tuning:

Sensitivity to jetting changes based on altitude, temperature, and modifications; detailed tuning guidance is crucial.

📚 Vehicle History

Yamaha Motorcycles:

Yamaha Motor Corporation has a long and storied history in motorcycle manufacturing, particularly in off-road racing, with iconic models like the YZ series.

Yz125 Lineage:

The YZ125 has been a cornerstone of Yamaha's motocross lineup for decades, undergoing continuous development and refinement to maintain its competitive edge.

2008 Yz125 Updates:

While specific updates for 2008 would be detailed in the manual, Yamaha typically made incremental improvements to suspension, engine tuning, and chassis components year-over-year.

Manufacturing Origin:

Yamaha motorcycles are primarily manufactured in Japan, with some production facilities globally.

🏆 Awards & Recognition

Motocross Awards:

The YZ125 platform has historically received numerous accolades and 'bike of the year' awards in the 125cc motocross class from various industry publications and racing organizations.

Manual Utility Rating:

Essential tool for owners and technicians, providing detailed information for effective maintenance and repair.