The 1999 Yamaha YZ125 is a performance-oriented Motocross Motorcycle renowned for its potent two-stroke engine and agile handling, a staple in the 125cc class. This model competed against other prominent motocross bikes of its era, such as the Honda CR125R, Kawasaki KX125, and Suzuki RM125. Yamaha has a significant legacy in motocross, and the YZ125 has been a key part of that history, continuously refined with advancements in engine technology, suspension, and chassis design. The 1999 iteration represents a generation focused on improving power delivery and suspension performance, making it a highly regarded machine for motocross racers and off-road enthusiasts. This comprehensive service manual provides detailed information for the 1999 Yamaha YZ125, covering complete service, repair, and maintenance procedures. It includes troubleshooting guides, diagnostic information, component removal and installation instructions, technical specifications, and clear diagrams essential for maintaining optimal performance and longevity. The manual details every major system, including the engine, transmission, fuel system, ignition, suspension, brakes, and electrical system, offering guidance from routine maintenance to complete overhauls. This resource is an indispensable tool for owners and technicians, ensuring accurate and efficient upkeep of the YZ125. 🏷️ Basic Information Identification Make: Yamaha Model: YZ125 Year: 1999 Vehicle Type: Motocross Motorcycle Codes Manual Product Name: Yamaha YZ 125 1999 Service Repair Workshop Manual PDF Download 👋 Introduction Market Position Category: Performance Motocross Motorcycle Target Audience: Motocross racers, off-road enthusiasts, and Yamaha YZ125 owners seeking to maintain or repair their machine. Competitive Analysis Rivals: Competed against models like the Honda CR125R, Kawasaki KX125, and Suzuki RM125 of the same era. Key Features Performance Focus: Renowned for its potent two-stroke engine and agile handling, a staple in the 125cc class. Manual Value Essential Tool: Crucial for owners and technicians to perform accurate maintenance, diagnostics, and repairs, ensuring optimal performance and longevity. 📋 Manual Details Coverage Areas Primary Coverage: Complete service, repair, and maintenance procedures for the 1999 Yamaha YZ125. Secondary Coverage: Troubleshooting, diagnostics, component removal/installation, specifications, and diagrams. Page Count Estimated Pages: 200-300 Manual Type Type: Service Manual / Workshop Manual / Repair Manual Language Language: English Format Format: PDF Download 📖 Manual Coverage Systems Covered Engine: Top-end (cylinder, piston, rings), bottom-end (crankshaft, connecting rod, bearings), lubrication, cooling, and exhaust systems. Transmission: Clutch, gearbox (gear selection, bearings, shafts), and final drive (chain, sprockets). Fuel System: Carburetor (disassembly, cleaning, adjustment, jetting), fuel tank, fuel lines, and fuel petcock. Ignition System: CDI unit, ignition coil, spark plug, wiring, and timing. Suspension: Front forks (disassembly, oil change, seal replacement, damping adjustments), rear shock absorber (rebuild, spring preload). Brakes: Front and rear hydraulic disc brakes (caliper service, pad replacement, fluid flush, master cylinder). Electrical System: Wiring diagrams, lighting, battery, charging system (if applicable for diagnostics), and switches. Cooling System: Radiator, coolant hoses, and water pump (if applicable). Frame And Bodywork: Frame inspection, handlebars, levers, footpegs, seat, fuel tank, and body panels. Procedures Included Maintenance: Routine checks, oil changes, filter replacements, chain adjustment, spark plug replacement, air filter cleaning/replacement. Troubleshooting: Diagnostic flowcharts and common problem identification for starting, running, and electrical issues. Repair: Detailed instructions for component disassembly, cleaning, inspection, repair, and reassembly of all major systems. Overhaul: Complete engine and transmission overhaul procedures. Specifications: Torque values, clearances, fluid capacities, and tolerances for all components. Wiring Diagrams: Comprehensive electrical system wiring schematics. Tool Requirements: Identification of special tools required for specific procedures. Technical Depth Depth: Comprehensive, covering basic maintenance to full engine and transmission rebuilds. Suitable for both home mechanics and professional technicians. 📊 Manual Specifications File Format Format: PDF (Portable Document Format) Searchable: Likely searchable text within the PDF for efficient information retrieval. Print Quality Quality: High-resolution scans of original documentation, ensuring clarity of text and diagrams. Binding Type Binding: N/A (Digital PDF download) Paper Type Paper Type: N/A (Digital PDF download) ⚙️ Engine Specifications Primary Engine Type: Liquid-cooled, 2-stroke, reed valve inducted Displacement: 124cc Bore X Stroke: 54.0 mm x 54.5 mm Compression Ratio: 8.7:1 (nominal, subject to variations) Cylinder Head: Aluminum alloy Crankshaft: Forged steel Piston: Aluminum alloy, two-ring design Performance Horsepower: Approximately 33-35 HP (subject to tuning and measurement conditions) Torque: Approximately 17-18 lb-ft (subject to tuning and measurement conditions) Fuel System Carburetor Model: Mikuni VM28SS (likely specification, manual will confirm) Fuel Type: Unleaded gasoline with appropriate octane rating (e.g., 91+) Fuel Mixture: Requires 2-stroke engine oil mixed with gasoline (typically 20:1 or 32:1 ratio, manual will specify) Lubrication Type: Premixed fuel/oil or automatic injection system (manual will detail specific design) 🔧 Transmission Standard Type: 6-speed constant mesh Features Clutch: Wet, multiple-disc, cable-actuated Final Drive: Chain drive 📐 Dimensions Exterior Length: Approx. 2180 mm (85.8 in) Width: Approx. 820 mm (32.3 in) Height: Approx. 1270 mm (50.0 in) Weights Dry Weight: Approx. 93 kg (205 lbs) Wet Weight: Approx. 100 kg (220 lbs) (estimated, with fluids) Fuel Tank Capacity: Approx. 8.0 Liters (2.1 Gallons)...