🏷️ Basic Information

Make:

Yamaha

Model:

YZ125

Model Years Covered:

1995, 1996, 1997

Chassis Codes:

4GD1, 4GD2, 4GD3 (specific to model years)

Engine Codes:

4JT (typical for this generation)

👋 Introduction

Positioning:

The Yamaha YZ125 is a legendary motocross and off-road competition motorcycle renowned for its lightweight chassis, potent 125cc two-stroke engine, and agile handling. This manual serves owners and mechanics who maintain these performance-oriented machines.

Competitors 1995-1997:

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

Key Features Vehicle:

Lightweight aluminum frame (later models), powerful reed-valve inducted two-stroke engine, advanced suspension systems, strong braking performance, competitive motocross platform.

Key Features Manual:

Instant access to detailed repair procedures, component specifications, diagnostic information, and torque settings crucial for maintaining peak performance and longevity of the YZ125.

📋 Manual Details

Primary Coverage:

Comprehensive workshop service and repair

Secondary Coverage:

Maintenance, diagnostics, troubleshooting, and adjustments

Estimated Page Count:

300-400 pages (typical for a full workshop manual)

Type:

Workshop Service Repair Manual

Language:

English

Format:

Instant Download (likely PDF)

📖 Manual Coverage

Engine:

Top-end rebuild, bottom-end overhaul, lubrication system, cooling system (if applicable to model year), fuel system (carburetor, intake), exhaust system, ignition system, engine tuning and diagnostics.

Transmission:

Clutch system, gearbox disassembly and reassembly, gear shifting mechanism, lubrication.

Suspension:

Front fork (KYB/Showa specification depending on model variant), rear shock absorber, linkage system, springs, damping adjustments, seal replacement.

Brakes:

Front and rear brake systems (hydraulic disc), caliper overhaul, master cylinder service, fluid bleeding, pad replacement, rotor inspection.

Electrical:

Wiring diagrams, ignition system components (CDI, coil, stator, spark plug), lighting (if applicable), troubleshooting electrical faults.

Chassis And Frame:

Frame inspection, steering head bearing service, swingarm overhaul, wheel bearing replacement, footpeg and lever assembly.

Bodywork:

Fairing removal and installation, seat, fuel tank, fenders, graphics.

Routine Maintenance:

Oil changes, air filter cleaning/replacement, chain adjustment and lubrication, spark plug checks, coolant checks (if applicable).

Engine Overhaul:

Piston and ring replacement, cylinder honing, crankcase assembly, seal and gasket replacement, valve clearance adjustment (if 4-stroke, but YZ125 is 2-stroke, so power valve system adjustment/cleaning).

Suspension Service:

Fork seal replacement, oil changes, shock absorber rebuild, spring setting adjustments.

Brake System Repair:

Brake pad replacement, caliper servicing, master cylinder rebuild, brake line replacement, bleeding procedures.

Troubleshooting:

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

Assembly And Disassembly:

Step-by-step guides for complete disassembly and reassembly of all major components.

Depth:

Complete rebuilds, advanced diagnostics, component-level repair, and detailed specifications.

📊 Manual Specifications

File Format:

PDF (Portable Document Format) is standard for instant downloads, offering high compatibility.

Print Quality:

Designed for clear printing with high-resolution diagrams and text. Suitable for professional workshop use.

Binding Type:

N/A (Instant Download, not a physical product)

Paper Type:

N/A (Instant Download, not a physical product)

⚙️ Engine Specifications

Engine Type:

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

Displacement:

124cc

Bore X Stroke:

54.0 mm x 54.5 mm (typical)

Compression Ratio:

Approximately 8.4:1 (varies by year and specific model tuning)

Power Valve System:

Yamaha Power Valve System (YPVS) for improved low-to-mid range power delivery.

Horsepower Estimated:

Approximately 35-40 HP (at crankshaft, varies by year and tuning)

Torque Estimated:

Approximately 19-22 lb-ft (at crankshaft, varies by year and tuning)

Carburetor:

Mikuni TM38 flat-slide carburetor (typical).

Fuel Type:

Unleaded gasoline (min. 91 octane recommended), mixed with 2-stroke oil.

Fuel Oil Ratio:

Typically 20:1 or 25:1, depending on riding conditions and oil type (refer to manual for precise specification).

Lubrication Type:

Premix (fuel and oil mixture) for crankcase lubrication. Separate gearbox oil.

Gearbox Oil Type:

Yamalube 10W-30 or equivalent API SG, SAE 10W-30 (refer to manual for exact specification).

Ignition System:

CDI (Capacitor Discharge Ignition).

Spark Plug Type:

NGK BR9ES or equivalent (typical, refer to manual).

🔧 Transmission

Transmission Type:

Constant-mesh 6-speed sequential.

Optional Transmissions:

N/A (standard configuration for YZ125).

Clutch Type:

Wet, multiple disc clutch, cable operated.

Gear Ratios:

Detailed gear ratios for each of the 6 speeds are provided in the manual.

📐 Dimensions

Length:

Approximately 2165 mm (typical, refer to manual for exact year)

Width:

Approximately 820 mm (typical, refer to manual for exact year)

Height:

Approximately 1275 mm (typical, refer to manual for exact year)

Wheelbase:

Approximately 1475 mm (typical, refer to manual for exact year)

Ground Clearance:

Approximately 330 mm (typical, refer to manual for exact year)

Seat Height:

Approximately 985 mm (typical, refer to manual for exact year)

Dry Weight:

Approximately 92 kg (typical, refer to manual for exact year)

Wet Weight:

Approximately 98 kg (with all fluids, typical)

Fuel Tank Capacity:

8.0 Liters (approx. 2.1 US gal)

Coolant Capacity:

0.75 Liters (approx. 0.79 US qt)

🛡️ Safety Features

Safety Ratings:

N/A (Motocross/Off-road competition vehicle, not typically subjected to DOT/NHTSA safety ratings for street use.)

Active Safety Features:

Powerful hydraulic disc brakes, responsive suspension for stability, strong frame for predictable handling.

Passive Safety Features:

Ergonomically designed seating position, robust build quality for impact resistance.

💡 Technology Features

Infotainment System:

N/A (This is a purebred competition off-road motorcycle, no infotainment features).

Driver Assistance Systems:

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

Connectivity Features:

N/A (No connectivity features like Bluetooth or Wi-Fi).

🔧 Maintenance

Oil Change Interval:

Gearbox oil: Every 10-15 hours of riding or annually. Engine oil (premix): Continuous as part of fuel. Check transmission oil level before each ride.

Air Filter Maintenance:

Clean and re-oil air filter every 5-10 hours of riding, or more frequently in dusty conditions. Replace filter element annually or as needed.

Spark Plug Replacement:

Check and clean spark plug every 5-10 hours. Replace as needed, or annually for optimal performance.

Chain Lubrication Adjustment:

Lubricate chain every 5-10 hours. Adjust chain tension every 5-10 hours or as per manual specification.

Engine Rebuild Interval:

Top-end rebuild (piston, rings) typically every 40-60 hours of hard riding. Full engine rebuild based on usage and component wear.

Coolant Type:

High-quality ethylene glycol-based antifreeze coolant, diluted with distilled water to a 50/50 ratio. Specific coolant specifications provided in the manual.

Brake Fluid Type:

DOT 3 or DOT 4 hydraulic brake fluid (refer to manual for exact specification).

2 Stroke Oil Type:

High-quality JASO FD, API TC rated 2-stroke engine oil specifically designed for competition motorcycles.

Common Wear Items:

Clutch plates, piston rings, seals (fork, engine), swingarm bearings, wheel bearings, brake pads, chain and sprockets.

Typical Problems:

Carburetor jetting sensitivity to altitude and temperature, power valve operation can require cleaning/adjustment, fork seal leaks, clutch wear. Manual provides solutions.

📚 Vehicle History

Yamaha Heritage:

Yamaha has a long and storied history in motorcycle racing, particularly in motocross, with the YZ line being a cornerstone of their off-road performance reputation since the 1970s.

Yz125 Evolution 1995-1997:

This generation (1993-1997) saw significant development. The 1995 model continued to refine the liquid-cooled 2-stroke engine and featured an aluminum frame introduced in previous years. These models were highly competitive in their class.

Production Era:

The YZ125 has been in continuous production for decades, with the 1995-1997 models representing a key phase in its development.

Manufacturing Location:

Typically manufactured in Japan by Yamaha Motor Company.

🏆 Awards & Recognition

Motocross Awards 1995-1997:

The YZ125 was consistently a top contender in 125cc class motocross racing during these years, often winning championships and magazine shootouts for its performance and handling.

Magazine Ratings:

Regularly received high ratings from motorcycle publications like Dirt Rider, Transworld Motocross, and Cycle World for its class-leading power and chassis dynamics.

Certifications:

N/A (Not applicable for off-road competition vehicles).