🏷️ Basic Information

Make:

Yamaha

Model:

YZ125

Year:

2008

Model Code:

YZ125X

Generation:

Third Generation (2002-2014)

Oem Manual Part Number:

N/A (as the provided product is a PDF, not a specific OEM part number reference)

👋 Introduction

Market Position:

The 2008 Yamaha YZ125 is a highly competitive 125cc two-stroke motocross motorcycle, known for its lightweight chassis, potent engine, and user-friendly handling. It targets both aspiring amateur racers and seasoned riders seeking a nimble and powerful platform for competition and recreational riding.

Competitive Analysis:

Competes directly with other major Japanese manufacturers' 125cc motocross offerings, such as the Honda CR125R (though its production ended around this period), Suzuki RM125, and Kawasaki KX125. Yamaha's YZ125 is often praised for its strong low-to-mid-range power delivery compared to some rivals, coupled with Yamaha's renowned chassis dynamics and reliability.

Key Features:

Liquid-cooled, reed valve inducted, two-stroke engine; Yamaha Power Valve System (YPVS) for optimized powerband; aluminum frame; adjustable KYB suspension components; lightweight design; potent performance for its class.

📋 Manual Details

Coverage Areas:

Complete Yamaha YZ125 service, repair, and workshop procedures for the 2008 model year.

Page Count:

Estimated 300-400 pages (typical for a comprehensive OEM service manual of this era).

Manual Type:

OEM Factory Service/Repair/Workshop Manual

Language:

English

Format:

PDF

📖 Manual Coverage

Systems Covered:

Engine overhaul, transmission, clutch, cooling system, fuel system (carburetion), ignition system, chassis, suspension (front and rear), brakes (front and rear), electrical system, wiring diagrams, troubleshooting, specifications, periodic maintenance, disassembly/assembly procedures, bodywork.

Procedures Included:

Detailed step-by-step instructions for all repair and maintenance tasks, including engine rebuilding (piston, rings, cylinder, crankshaft, bearings), transmission gear replacement, clutch service, carburetor tuning and rebuilding, suspension fork and shock absorber servicing, brake caliper and master cylinder overhauling, wheel bearing replacement, chain and sprocket replacement, electrical component testing, and chassis component adjustments.

Technical Depth:

Comprehensive, from basic maintenance checks and adjustments to complete engine and chassis rebuilds. Includes diagnostic procedures, torque specifications, clearances, and detailed troubleshooting guides for common and uncommon issues.

📊 Manual Specifications

File Format:

PDF

Print Quality:

High-resolution scans of original OEM manual, optimized for digital viewing and printing of individual pages. Includes clear diagrams and illustrations.

Binding Type:

N/A (Digital PDF format)

Paper Type:

N/A (Digital PDF format)

⚙️ Engine Specifications

Engine Type:

Liquid-cooled, 2-stroke, reed valve induction

Displacement:

124cc

Bore X Stroke:

54mm x 54.5mm

Compression Ratio:

9.7:1 (typical for this model year)

Carburetor:

Keihin PWK38S, 38mm throttle slide flat-action carburetor with power jet

Ignition:

CDI (Capacitor Discharge Ignition)

Ypvs:

Yamaha Power Valve System (YPVS) integrated into exhaust port.

Horsepower:

Approximately 35-38 HP at peak RPM (estimated, exact figure often varies by dyno and testing conditions).

Torque:

Approximately 17-19 lb-ft at peak RPM (estimated).

Fuel Type:

Unleaded gasoline (91 octane or higher recommended)

Fuel Mixture:

50:1 (Premium 2-stroke oil to gasoline)

🔧 Transmission

Transmission Type:

5-speed constant mesh

Clutch Type:

Wet, multiple-disc

Final Drive:

O-ring sealed chain, 13/49 (4.23) final gear ratio (stock)

Gear Ratios:

1st: 2.615 (34/13), 2nd: 1.933 (29/15), 3rd: 1.500 (27/18), 4th: 1.235 (21/17), 5th: 1.000 (20/20) (typical values)

Clutch Lever Free Play:

10-15mm (3/8 - 5/8 in.) at lever end

📐 Dimensions

Overall Length:

2,135 mm (84.1 in.)

Overall Width:

820 mm (32.3 in.)

Overall Height:

1,270 mm (50.0 in.)

Seat Height:

970 mm (38.2 in.)

Wheelbase:

1,475 mm (58.1 in.)

Ground Clearance:

370 mm (14.6 in.)

Wet Weight:

97 kg (214 lbs) (approximate, with all necessary operating fluids)

Fuel Tank Capacity:

8.0 L (2.1 US gal)

Oil Tank Capacity:

1.3 L (1.4 US qt)

🛡️ Safety Features

Safety Ratings:

Not applicable for off-road competition motorcycles in the same way as street vehicles. Emphasis is on rider protection and machine integrity during competitive use.

Active Features:

Responsive braking systems, predictable power delivery, stable chassis geometry, and effective suspension contribute to rider control and accident avoidance.

Passive Features:

Durable frame construction, impact-absorbing seat, and handguards (often aftermarket) are key passive safety elements.

💡 Technology Features

Infotainment System:

Not applicable. This is a pure motocross racing machine with no comfort or convenience technology features.

Driver Assistance Features:

Not applicable.

Connectivity Options:

Not applicable.

🔧 Maintenance

Air Filter Cleaning:

After every 5-10 hours of riding or as needed based on conditions.

Spark Plug Inspection:

Every 10-20 hours of riding, replace as needed.

Piston And Ring Replacement:

Recommended every 40-60 hours of racing use, or based on compression loss.

Clutch Inspection:

Every 10-20 hours of riding, check for wear and proper operation.

Chain And Sprocket Inspection:

Every 5-10 hours of riding, check for wear and proper tension.

Engine Oil:

Yamaha Genuine 2-stroke oil or equivalent (e.g., Yamalube 2R), mixed at 50:1 ratio with fuel.

Transmission Oil:

Yamalube Gear Oil 10W-30 or SAE 80 hypoid gear oil (API GL-4). Capacity: 0.65 L (0.69 US qt).

Coolant:

Yamaha All-Weather Water Cooled Engine Coolant or equivalent permanent type antifreeze (50% solution with distilled water).

Fork Oil:

Yamaha Genuine Fork Oil G10 or SAE 0W-20 equivalent. Capacity: 543 ml (18.4 US oz).

Known Issues:

As with most high-performance two-strokes of this era, regular top-end rebuilds are crucial. Common issues can include worn piston rings or piston, carbon buildup in the exhaust port and YPVS mechanism, clutch wear, and carburetor jetting sensitivity to altitude and temperature changes. Proper jetting is key to maximizing performance and engine longevity.

📚 Vehicle History

Brand Heritage:

Yamaha has a long and storied history in motorcycle racing, particularly in motocross and Grand Prix racing. The YZ line, introduced in the 1970s, is a cornerstone of their off-road performance heritage.

Model Evolution:

The YZ125 has undergone continuous development, with significant updates occurring in 2002 for the third generation. This generation featured an all-new aluminum frame, revised engine, and updated suspension, setting it apart for many years. The 2008 model represents a refinement of this successful platform.

Production Period:

The YZ125 has been in continuous production for decades. The 2008 model was manufactured during that calendar year for the global market.

Manufacturing Location:

Japan (primary manufacturing, though assembly may occur in other regions).

🏆 Awards & Recognition

Recognitions:

While specific awards for the 2008 model are not widely publicized, the Yamaha YZ125 platform has consistently been recognized by motocross publications and riders for its performance, handling, and competitive spirit within the 125cc class for many years.

Industry Ratings:

Consistently ranked highly in head-to-head comparisons in the 125cc class for its balance of power and handling characteristics.

Certifications:

Not applicable for off-road motorcycles.