Segment:
Motocross / Off-Road Competition
Target Audience:
Competitive motocross riders and dedicated off-road enthusiasts.
Competitors 2000:
Honda CR125R, Kawasaki KX125, Suzuki RM125, KTM 125 EXC.
Engine Type:
High-revving two-stroke power.
Suspension Performance:
Renowned for its plush and capable suspension.
Comprehensiveness:
Covers all aspects of the motorcycle, from routine maintenance to complete engine rebuilds.
Diagrams Illustrations:
Richly illustrated with detailed diagrams and photographs.
Torque Specs Accuracy:
Precise torque values essential for engine longevity and safety.
Engine:
Complete engine teardown, rebuild, and tuning for the 125cc two-stroke powerplant.
Transmission:
Gearbox disassembly, inspection, and reassembly, including clutch and shifting mechanisms.
Suspension:
Front fork (Kayaba USD) and rear Monoshock (Monocross system) overhaul, adjustments, and service.
Brakes:
Front and rear hydraulic disc brake system servicing, including caliper, master cylinder, and fluid replacement.
Electrical:
Wiring diagrams, ignition system troubleshooting, lighting, and charging system components.
Fuel System:
Carburetor (Mikuni VM34) disassembly, cleaning, tuning, and fuel line servicing.
Cooling System:
Radiator and coolant flow maintenance for the liquid-cooled engine.
Exhaust System:
Pipe and silencer inspection and maintenance.
Chassis Frame:
Frame inspection, steering head bearing service, and swingarm maintenance.
Maintenance:
Scheduled maintenance tasks, including oil changes, filter replacements, and chain lubrication.
Troubleshooting:
Systematic diagnostic procedures for common and uncommon issues.
Repair:
Detailed, step-by-step instructions for component repair and replacement.
Rebuild:
Comprehensive engine and transmission rebuild procedures.
Specifications:
Torque specifications for all fasteners, clearances, and settings.
Diagrams:
Illustrated part diagrams for easy identification and ordering.
Tuning:
Carburetor jetting and ignition timing adjustments for optimal performance.
Depth:
Expert-level detail suitable for professional mechanics and serious enthusiasts.
Diagnostic Charts:
Extensive diagnostic flowcharts and symptom-cause-remedy tables.
Special Tools:
Identification and usage of specialized tools required for specific procedures.
Engine Type:
Liquid-cooled, 2-stroke, Reed valve, YPVS controlled
Bore X Stroke:
54 mm x 54.5 mm
Carburetor:
Mikuni VM34SS
Ignition:
CDI (Capacitor Discharge Ignition)
Horsepower Est:
~35 hp @ 11,000 rpm (Estimated)
Torque Est:
~17 lb-ft @ 10,000 rpm (Estimated)
Fuel Type:
Unleaded gasoline (91 octane or higher recommended)
Premix Ratio:
50:1 with high-quality 2-stroke engine oil
Type:
Constant-mesh 6-speed sequential
Clutch:
Wet, multiple-disc, cable-actuated
Gear Ratios:
Detailed in manual, typically close-ratio for motocross performance.
Features:
N/A (Competition motocross bike, no infotainment features).
Features:
N/A (Competition motocross bike, no electronic rider aids).
Features:
N/A (Competition motocross bike, no connectivity features).
Ypvs:
Yamaha Power Valve System (YPVS) provides improved low-to-mid range power delivery and broader torque curve.
Oil Change:
Refer to manual for specific intervals based on riding conditions; typically every 10-20 hours for high-performance use.
Air Filter Cleaning:
Frequent cleaning/replacement recommended, especially in dusty conditions (refer to manual).
Spark Plug Replacement:
Check and replace as needed, typically every 20-40 hours of riding.
Top End Rebuild:
Recommended every 40-80 hours for optimal performance in racing applications.
Engine Oil:
Yamalube 2R or equivalent high-performance 2-stroke synthetic oil (50:1 premix ratio).
Transmission Oil:
Yamalube Hypoid Gear Oil GL-4 (SAE 80W) or equivalent.
Coolant:
Yamaha Super Coolant or equivalent ethylene glycol-based antifreeze (50% solution).
Brake Fluid:
DOT 3 or DOT 4 hydraulic brake fluid.
Carburetor Jetting:
Sensitivity to altitude and temperature changes; requires proper jetting for optimal performance.
Clutch Wear:
Clutch plates can wear relatively quickly with aggressive riding; proper adjustment and timely replacement are crucial.
Suspension Seals:
Fork and shock seals can be susceptible to wear over time, leading to leaks.
Yamaha Motorcycles:
Yamaha has a long-standing reputation for performance and innovation in motorcycle manufacturing, particularly in the off-road and racing sectors.
Yz Series:
The YZ125 is part of Yamaha's iconic YZ motocross line, which has seen continuous development and success in professional racing for decades.
2000 Model Updates:
The 2000 model featured refinements to the suspension, chassis, and engine tuning compared to previous years, building on a successful platform.
Manufacturing Origin:
Japan
Motocross Performance:
The YZ125 platform has a history of numerous national and regional championships in its class.
Magazine Reviews:
Consistently praised by motorcycle publications for its performance, handling, and competitive edge.
Manual Quality:
Official factory documentation, ensuring accuracy and completeness.
