🏷️ Basic Information

Make:

Yamaha

Model:

YZ125

Year:

2010

Vehicle Type:

Motocross Motorcycle

Engine Code Identifier:

YZ125 (specific VIN prefix may vary based on region, consult dealer for precise lookup)

👋 Introduction

Class:

Performance Motocross Motorcycle

Segment:

125cc Two-Stroke Motocross

Key Competitors:

KTM 125 SX, Honda CR125R (though Honda discontinued its 125 two-stroke earlier), Suzuki RM125 (discontinued by 2008), Kawasaki KX125 (discontinued by 2007).

Engine Type:

Liquid-cooled, 2-stroke, reed valve, single-cylinder

Chassis Design:

Lightweight aluminum bilateral beam frame

Suspension Technology:

High-performance Kayaba Speed Sensitive System (SSS) front forks and Monoshock rear suspension.

📋 Manual Details

Primary Coverage:

Complete repair, maintenance, and troubleshooting for the 2010 Yamaha YZ125.

Specific Systems Covered:

Engine, drivetrain, chassis, suspension, brakes, electrical system, fuel system, cooling system.

Total Pages:

161

Type:

Factory Service Manual / Repair Manual

Language:

English

Format:

Digital Download (PDF)

📖 Manual Coverage

Engine Mechanical:

Complete engine teardown, assembly, cylinder head, piston, crankshaft, connecting rod, all internal components.

Fuel And Ignition:

Carburetor (Mikuni VM34SS), fuel tank, fuel lines, CDI ignition system, spark plug specifications.

Transmission And Drivetrain:

Clutch operation and adjustment, gearbox disassembly and reassembly, chain drive maintenance.

Suspension:

Front fork (Kayaba 48mm USD) overhaul, rear shock absorber (Kayaba) service, suspension adjustments.

Brakes:

Front and rear hydraulic disc brake system service, caliper overhaul, bleeding procedures, pad replacement.

Electrical System:

Wiring diagrams, lighting system, ignition system, battery maintenance, troubleshooting electrical faults.

Cooling System:

Radiator, coolant, hoses, thermostat (if applicable to two-stroke design).

Chassis And Frame:

Frame inspection, steering head bearing service, wheel bearing replacement.

Maintenance:

Regular service checks, lubrication points, filter replacement, chain adjustment, brake fluid changes.

Troubleshooting:

Diagnostic flowcharts for common issues, engine performance problems, starting difficulties, electrical faults.

Repair:

Complete step-by-step instructions for all major component repairs and replacements.

Rebuilds:

Comprehensive guidance for complete engine and suspension rebuilds.

Adjustments:

Carburetor tuning, clutch adjustment, suspension setup, cable adjustments.

Depth:

Expert Level - Suitable for professional mechanics and experienced DIY enthusiasts. Covers all aspects from basic maintenance to complete engine and chassis overhauls.

Diagnostic Capabilities:

Detailed troubleshooting guides for identifying and resolving mechanical and electrical issues.

Visual Aids:

Includes clear photographs and detailed part diagrams to illustrate procedures.

📊 Manual Specifications

Format Details:

PDF (Portable Document Format) - High resolution, searchable text, printable pages.

Print Readability:

Excellent. Designed for clear printing of text and diagrams.

Binding Type For Digital:

N/A (Digital download)

Paper Type For Digital:

N/A (Digital download)

⚙️ Engine Specifications

Engine Type:

Liquid-cooled, 2-stroke, reed valve, single-cylinder

Bore X Stroke:

54.0 mm x 54.5 mm

Displacement:

124 cc

Compression Ratio:

8.6:1 (nominal)

Intake System:

Reed valve intake

Carburetor:

Mikuni VM34SS

Ignition:

Digital CDI (Capacitor Discharge Ignition)

Starting System:

Primary kick

Lubrication:

Premixed fuel and oil (2-stroke oil ratio typically 20:1 or 32:1, consult manual for exact spec)

Horsepower:

Approx. 39-40 HP (at crankshaft, typical for this class)

Torque:

Approx. 2.4 kgf-m / 23.5 Nm (at crankshaft, typical for this class)

Fuel Type:

Unleaded gasoline

Fuel Tank Capacity:

7.0 Liters (1.85 US gal)

🔧 Transmission

Type:

Constant mesh 6-speed

Clutch:

Wet, multi-plate, cable-actuated

Final Drive:

Chain drive, RK520MS O-ring chain (example chain type)

📐 Dimensions

Overall Length:

2170 mm (85.4 in)

Overall Width:

825 mm (32.5 in)

Overall Height:

1280 mm (50.4 in)

Seat Height:

985 mm (38.8 in)

Wheelbase:

1475 mm (58.1 in)

Ground Clearance:

355 mm (14.0 in)

Dry Weight:

97 kg (213.8 lbs)

Wet Weight:

Approx. 104 kg (229 lbs)

Front Tire Size:

80/100-21 51M

Rear Tire Size:

110/90-19 62M

Wheelbase Type:

Spoked aluminium wheels

Wheel Bolt Pattern:

N/A (Hub mounted)

🛡️ Safety Features

Safety Class:

Off-road competition vehicle, not intended for street use. No NHTSA/Euro NCAP ratings.

Braking System:

Hydraulic disc brakes front and rear.

Frame Construction:

High-tensile aluminum alloy frame for rigidity and impact absorption.

💡 Technology Features

Infotainment Features:

N/A (Performance Motocross Motorcycle, no infotainment system)

Assistance Systems:

N/A (Performance Motocross Motorcycle, no electronic rider aids like ABS or traction control)

Connectivity Features:

N/A (Performance Motocross Motorcycle, no connectivity features)

Ignition Control:

Digital CDI provides precise ignition timing for optimal power delivery across the rev range.

🔧 Maintenance

Oil Change Interval:

Recommended every 10-15 hours of riding or annually. Consult manual for precise recommendation.

Air Filter Cleaning:

Recommended every 5-10 hours of riding, or more frequently in dusty conditions. Specific cleaning procedure detailed in manual.

Spark Plug Inspection:

Recommended every 10-20 hours of riding. Manual specifies plug type and gap.

Chain Lubrication Adjustment:

Recommended every 5-10 hours of riding or after washing. Check tension regularly.

Top End Rebuild:

Intervals vary based on usage, typically 30-50 hours for aggressive riding. Manual provides detailed overhaul procedures.

Engine Oil:

2-stroke premix oil. Yamaha recommends Yamalube 2R or equivalent high-quality 2-stroke racing oil. Oil ratio: 20:1 or 32:1 depending on conditions/preference (consult manual).

Transmission Oil:

Yamaha recommends Yamalube Gear Oil (e.g., 10W-30 or 10W-40, check manual for specific viscosity) or equivalent motorcycle-specific transmission oil. Capacity: 0.65 Liters (0.69 US qt).

Coolant:

A high-quality, permanent type coolant (antifreeze) mixed with distilled water at a 50:50 ratio. Yamaha recommends Yamalube Coolant.

Brake Fluid:

DOT 4 hydraulic brake fluid (DOT 3 may be acceptable, but DOT 4 is preferred for higher boiling point). Ensure it is fresh and clean.

Common Wear Items:

Clutch plates, piston rings, seals, bearings (crankshaft, wheel, steering head), chain and sprockets, brake pads.

Carburetor Tuning:

Requires regular cleaning and tuning due to its nature as a high-performance carbureted engine, especially with changes in altitude or temperature.

Power Valve System:

The YPVS (Yamaha Power Valve System) can accumulate carbon deposits, requiring periodic cleaning to maintain optimal performance. Manual details its inspection and cleaning.

📚 Vehicle History

Heritage:

Yamaha has a long and storied history in motocross, with the YZ series being a cornerstone of their off-road performance for decades.

Yz Series Legacy:

The YZ125 has been a dominant force in the 125cc class, known for its potent two-stroke power delivery and agile handling. Updates through the years focused on engine performance, chassis refinement, and suspension technology.

Production Period:

Ongoing since the 1970s. The 2010 model represents a mature iteration of the YZ125 platform.

Manufacturing Location:

Japan (typical for Yamaha models)

🏆 Awards & Recognition

Class Performance Awards:

The YZ125 has historically been recognized in industry publications and by riders for its class-leading performance and handling in the 125cc two-stroke category.