🏷️ Basic Information

Make:

Yamaha

Model:

YZ125

Model Variant:

YZ125

Year:

2006

Engine Type:

2-Stroke

Engine Displacement:

125cc

Market Segment:

Motocross / Off-Road Competition

Vin Code Year:

6

👋 Introduction

Positioning:

The Yamaha YZ125 has consistently been a benchmark in the highly competitive 125cc two-stroke motocross class, known for its potent engine, agile chassis, and rider-friendly power delivery.

Competitors 2006:

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

Performance Focus:

Designed for peak performance on the motocross track, emphasizing power-to-weight ratio and handling.

Technology Highlights:

Likely features an aluminum frame, advanced suspension components (e.g., KYB SSS forks), and potent 125cc reed-valve two-stroke engine with YPVS (Yamaha Power Valve System).

📋 Manual Details

Primary Coverage:

Yamaha YZ125 2006 Model

Extended Coverage Note:

Will work with similar years/models, specific links provided for other years.

Estimated Page Count:

Refer to original manual specification (typically 300-500 pages for a complete service manual)

Type:

Service Repair Workshop Manual

Language:

English

Format:

Digital (PDF implied by typical online sales)

📖 Manual Coverage

Engine Overhaul:

Complete engine disassembly, inspection, repair, and reassembly procedures.

Top End Rebuild:

Piston, rings, cylinder, cylinder head, and exhaust power valve maintenance and repair.

Crankshaft And Connecting Rod:

Inspection, bearing replacement, and connecting rod service.

Cooling System:

Radiator, hoses, water pump, and coolant specifications.

Fuel System:

Carburetor (Mikuni VM series likely) disassembly, cleaning, jetting, and adjustment. Fuel pump and lines.

Ignition System:

CDI unit, spark plug, ignition timing, and stator coil specifications.

Transmission:

Gearbox disassembly, inspection, gear replacement, clutch (wet multi-plate) service, and lubrication.

Drivetrain:

Final drive chain and sprockets inspection and replacement guidelines.

Suspension Front:

Fork (likely KYB SSS or similar) disassembly, oil change, seal replacement, and valving adjustments.

Suspension Rear:

Monoshock (likely KYB or similar) overhaul, linkage system service, and shock absorber adjustments.

Brakes Front:

Caliper, master cylinder, brake lines, and rotor service and specifications.

Brakes Rear:

Caliper, master cylinder, brake lines, and rotor service and specifications.

Wheels And Tires:

Hubs, spokes, rims, bearings, and tire pressure recommendations.

Steering:

Handlebar, triple clamps, steering stem bearings, and steering damper (if applicable) service.

Electrical System:

Wiring diagrams, lighting (if applicable for specific regulations), fuses, and battery (if applicable).

Bodywork And Frame:

Seat, plastics, fuel tank, airbox, and frame inspection and maintenance.

Routine Maintenance:

Oil changes, filter cleaning/replacement, chain lubrication, spark plug checks.

Troubleshooting:

Diagnostic flowcharts and common problem diagnosis for engine, electrical, and chassis issues.

Component Replacement:

Detailed instructions for replacing major and minor components.

Assembly Disassembly:

Step-by-step guides for all major sub-assemblies.

Torque Specifications:

Precise torque values for critical fasteners throughout the motorcycle.

Diagnostic Procedures:

Procedures for checking ignition timing, compression, and fuel delivery.

Depth:

Comprehensive, covering all aspects from basic adjustments to complete engine rebuilds and suspension tuning.

📊 Manual Specifications

File Type:

PDF (Portable Document Format)

Searchability:

Typically text-searchable for quick information retrieval.

Quality:

High-resolution scans of original factory documentation, ensuring clarity of diagrams and text.

Binding:

N/A (Digital Format)

Paper:

N/A (Digital Format)

⚙️ Engine Specifications

Engine Configuration:

Single-cylinder, liquid-cooled, reed-valve, 2-stroke

Bore X Stroke:

53.8 mm x 54.7 mm (typical for this era YZ125)

Compression Ratio:

8.1:1 - 9.5:1 (typical, specific value in manual)

Reed Valve System:

YPVS (Yamaha Power Valve System) for optimized powerband.

Horsepower Estimate:

Approximately 38-42 HP (at crankshaft, depending on tuning and exhaust)

Torque Estimate:

Approximately 21-23 lb-ft (at crankshaft, depending on tuning)

Carburetor Model:

Mikuni TM38 (likely, or similar 38mm flat-slide carb)

Fuel Type:

Unleaded gasoline (91 octane or higher recommended)

2 Stroke Oil Ratio:

100:1 (or specified by Yamaha, requires pre-mix or oil injection)

🔧 Transmission

Type:

Constant-mesh 6-speed sequential

Clutch Type:

Wet, multiple-disc

Gear Ratios:

Specific ratios available in manual (e.g., 1st: 32/15, 2nd: 28/17, 3rd: 25/19, 4th: 23/20, 5th: 21/21, 6th: 19/22)

Final Drive:

Chain driven (specific sprocket sizes in manual)

Clutch Actuation:

Hydraulic or Cable (typically cable for YZ125)

Transmission Oil Type:

Yamaha Yamalube Gear Oil 10W-40 (or equivalent API SG, SAE 10W-40, API GL-4)

📐 Dimensions

Length:

Approx. 81.1 in (2060 mm)

Width:

Approx. 32.3 in (820 mm)

Height:

Approx. 50.6 in (1285 mm)

Wheelbase:

Approx. 57.9 in (1470 mm)

Ground Clearance:

Approx. 14.4 in (365 mm)

Dry Weight:

Approx. 202 lbs (92 kg)

Wet Weight:

Approx. 215 lbs (97.5 kg) (with all fluids)

Fuel Capacity:

Approx. 2.1 Gallons (8.0 Liters)

🛡️ Safety Features

Safety Certification:

Designed for closed-course competition use; not street legal or safety certified for road use.

Braking System:

Hydraulic disc brakes front and rear for superior stopping power.

Frame Construction:

Lightweight and rigid aluminum alloy frame for improved handling and rider feedback.

💡 Technology Features

Infotainment System:

N/A (Competition dirt bike, no infotainment features)

Driver Assistance Features:

N/A (No electronic driver assistance features)

Connectivity Features:

N/A (No connectivity features)

Ypvs:

Yamaha Power Valve System (YPVS) electronically controlled exhaust power valve for improved torque and broader powerband.

Frame Material:

Aluminum Alloy Frame for lightness and rigidity.

Suspension Technology:

High-performance, adjustable suspension components, likely featuring Speed Sensitive System (SSS) technology on forks.

🔧 Maintenance

Air Filter Cleaning:

After every few rides or as needed based on conditions (specified in manual).

Spark Plug Inspection:

Every 10-20 hours of riding (specific plug type and gap in manual).

Chain Lubrication Adjustment:

Regularly, before each ride or every few hours, and check tension.

Engine Oil Change:

Specific intervals for transmission oil change (e.g., every 15-30 hours or as per manual).

Top End Rebuild Recommendation:

Typically recommended between 40-100 hours of aggressive riding, depending on usage and maintenance.

Engine Oil:

Yamaha Yamalube 2-stroke oil or equivalent API TC certified, JASO FD certified (pre-mix or injection).

Transmission Oil:

Yamaha Yamalube Gear Oil 10W-40 or equivalent API SG, SAE 10W-40, API GL-4.

Coolant Type:

High-quality, permanent type coolant (50/50 mix with distilled water).

Fork Oil Type:

Specific fork oil weight and level specified in the manual (e.g., KYB Suspension Oil SAE 0W-20 or equivalent).

Common Wear Items:

Clutch plates, piston rings, crank bearings, wheel bearings, steering head bearings, suspension seals.

Carburetor Cleaning:

Regular cleaning and proper jetting are crucial for optimal performance, especially with fuel variations.

📚 Vehicle History

Yamaha Motorsports:

Yamaha has a long and storied history in motorsports, particularly in motocross, with a legacy of innovation and performance dating back decades.

Yz Series Development:

The YZ125 has undergone continuous development, evolving from early air-cooled models to the liquid-cooled, high-performance machines of the 2000s, consistently pushing the boundaries of the 125cc class.

Production Period:

The YZ125 model line has been in continuous production since the 1970s, with significant updates occurring periodically.

🏆 Awards & Recognition

Motocross Class Standings:

The YZ125 has historically been a top contender in 125cc class racing and championship results.