🏷️ Basic Information

Make:

Yamaha

Model:

YZ125

Year:

2013

Vehicle Type:

Off-Road Motorcycle

Engine Type:

Two-Stroke

Chassis Code:

Often designated by a prefix like 'JY' followed by model and year specifics (e.g., JY4253)

Engine Code:

Typically found on the engine cases, e.g., 5XE-xxxxxx

👋 Introduction

Segment:

High-performance Motocross (MX) / Off-Road Competition

Target Audience:

Competitive MX riders, off-road enthusiasts, mechanics, and owners seeking detailed maintenance and repair information.

Key Competitors:

KTM 125 SX, Kawasaki KX125 (discontinued after 2005 but influential), Honda CR125R (discontinued after 2007 but influential), Suzuki RM125 (discontinued after 2007 but influential)

Yz125 Reputation:

Renowned for its nimble handling, potent 125cc two-stroke engine, and the highly acclaimed KYB Speed Sensitive System (SSS) front forks.

Manual Value Proposition:

Provides the critical factory-issued information necessary for maintaining peak performance, diagnosing issues, and performing complex repairs on the YZ125.

📋 Manual Details

Primary Coverage:

Complete repair and maintenance for the 2013 Yamaha YZ125

Component Coverage:

Engine, transmission, chassis, suspension, brakes, electrical system, fuel system, cooling system, bodywork

Total Pages:

163

Type:

Factory Service Manual / Repair Manual

Language:

English

Format:

Digital Download (PDF)

📖 Manual Coverage

Engine:

Comprehensive coverage including disassembly, assembly, inspection, and repair of all engine components (cylinder, piston, crankshaft, connecting rod, valve train, lubrication system, cooling system)

Transmission:

Clutch operation, gearbox disassembly and assembly, shift mechanism, lubrication, troubleshooting

Fuel System:

Carburetor disassembly, cleaning, adjustment, jetting, fuel tank, fuel lines, fuel pump (if applicable)

Ignition System:

CDI unit, spark plug specifications, ignition timing, troubleshooting ignition issues

Electrical System:

Wiring diagrams, battery maintenance, lighting, charging system, troubleshooting electrical faults

Suspension:

Front fork (KYB SSS - Speed Sensitive System) disassembly, assembly, oil levels, damping adjustments, rear shock absorber service and tuning

Brakes:

Front and rear hydraulic brake system service, caliper overhaul, master cylinder, brake fluid replacement, bleeding procedures, pad replacement

Cooling System:

Radiator maintenance, coolant specifications, water pump inspection and repair

Frame And Bodywork:

Frame inspection, removal and installation of body panels, seat, handlebars, footpegs

Maintenance:

Regular service, oil changes, filter cleaning/replacement, chain adjustment, spark plug replacement, general inspection

Troubleshooting:

Diagnostic procedures for common performance issues, starting problems, electrical faults, and mechanical failures

Repair:

Detailed step-by-step instructions for component repair and replacement, including complete engine tear-down and rebuild

Specifications:

Torque specifications for all fasteners, critical clearances, fluid capacities, and wear limits

Diagnostics:

Visual inspections, testing of electrical components, pressure testing (e.g., compression), and symptom-based troubleshooting guides

Depth:

Factory-level detail suitable for professional mechanics and experienced DIY enthusiasts, covering both routine maintenance and complete engine and chassis overhauls.

📊 Manual Specifications

Format:

PDF

Searchable:

Yes (text-searchable for quick access to information)

Quality:

High-resolution scans ensuring clarity of diagrams and text

Binding:

N/A (Digital Download)

Paper:

N/A (Digital Download)

⚙️ Engine Specifications

Engine Configuration:

Liquid-cooled, 125cc, 2-stroke, reed-valve induction, YPVS (Yamaha Power Valve System)

Bore X Stroke:

54 mm x 54.5 mm

Compression Ratio:

Approx. 8.2:1 to 9.4:1 (depending on specific YPVS setting and measurement)

Cylinder Design:

Perimeter-cased, plated cylinder with YPVS

Horsepower:

Estimated 35-40 HP at peak (actual figures vary)

Torque:

Estimated 18-20 lb-ft at peak (actual figures vary)

Carburetor:

Keihin PWK38S (38mm slide carburetor with throttle position sensor - TPS)

Fuel Type:

Unleaded gasoline, minimum 91 octane (RON+MON)/2

Oil Mixture:

Yamalube 2-stroke oil (or equivalent high-quality 2-stroke premix oil), typically 50:1 ratio

🔧 Transmission

Type:

5-speed constant-mesh

Clutch Type:

Wet, multiple-disc

Optional Gear Ratios:

N/A (Factory manual covers standard configuration)

Gearbox Lubricant:

Yamalube Hypoid Gear Oil GL-4 (or equivalent SAE 80 EP)

📐 Dimensions

Length:

Approx. 2,175 mm (85.6 in)

Width:

Approx. 825 mm (32.5 in)

Height:

Approx. 1,280 mm (50.4 in)

Wheelbase:

Approx. 1,475 mm (58.1 in)

Wet Weight:

Approx. 104 kg (229 lbs) (fully fueled)

Dry Weight:

Approx. 97 kg (214 lbs)

🛡️ Safety Features

Safety Ratings:

N/A (Motorcycles are not typically subjected to standardized crash testing like cars; safety is inherent in design and rider skill).

Braking System:

Hydraulic disc brakes front and rear for effective stopping power.

Frame Construction:

Strong aluminum alloy frame designed for rigidity and impact resistance.

💡 Technology Features

Infotainment System:

N/A (This is a competition motocross bike; no infotainment features.)

Assistance Systems:

N/A (No electronic driver assistance systems are present.)

Connectivity Features:

N/A (No connectivity features.)

Ypvs Technology:

Yamaha Power Valve System (YPVS) electronically controls exhaust port timing for improved power delivery across a wider RPM range.

Front Suspension Type:

KYB Speed Sensitive System (SSS) 48mm upside-down telescopic fork with adjustable compression and rebound damping.

Rear Suspension Type:

KYB Monoshock with adjustable spring preload, compression, and rebound damping.

🔧 Maintenance

Oil Change Frequency:

Every 10-15 hours of hard riding or as specified by riding conditions. Refer to manual for exact intervals.

Air Filter Cleaning:

After every few rides, or more frequently in dusty conditions. Critical for engine longevity.

Spark Plug Replacement:

Approximately every 20-30 hours of use, or as needed based on condition.

Engine Rebuild Timing:

Top-end rebuild (piston, rings) typically every 40-60 hours of racing, full engine rebuild much later. Manual provides guidelines.

Engine Oil Type:

2-stroke engine oil, JASO FD or higher performance specification.

Transmission Oil Type:

Yamalube Hypoid Gear Oil GL-4 or SAE 80 EP gear oil. Capacity: 0.63 Liters (0.67 US qt).

Coolant Type:

High-quality, permanent type coolant (ethylene glycol based) with distilled water. Capacity: 0.64 Liters (0.68 US qt).

Brake Fluid Type:

DOT 4 hydraulic brake fluid.

Common Wear Items:

Clutch plates, piston rings, air filter, spark plug, chain and sprockets, brake pads, fork seals.

Ypvs Care:

The Yamaha Power Valve System (YPVS) requires periodic cleaning to prevent carbon buildup, which can affect engine performance. The manual details this procedure.

Carburetor Tuning:

Proper jetting is crucial for optimal performance and engine health, especially with changes in altitude or temperature. The manual provides baseline settings and tuning guidance.

📚 Vehicle History

Yamaha Motorcycles:

Yamaha Motor Company, founded in 1955, has a long and storied history in motorsports, particularly in motocross and Grand Prix racing, known for innovation and performance.

Yz Series:

The YZ series has been a cornerstone of Yamaha's motocross lineup since its inception, consistently evolving with technological advancements to maintain competitiveness.

Yz125 Key Milestones:

Significant updates have included the introduction of the YPVS (Yamaha Power Valve System), advanced suspension technologies like SSS forks, and chassis refinements.

Manufacturing Location:

Primarily Japan

Production Years:

The YZ125 has been in continuous production since the 1970s, with the 2013 model representing a refined iteration of a long-standing competition machine.

🏆 Awards & Recognition

Motocross Prowess:

The YZ125, and its predecessors, have consistently been lauded in motorcycle publications and by professional riders for their performance, handling, and competitive edge in the 125cc class.