Vehicle Segment:
High-performance motocross motorcycle.
Competitors:
Honda CR250R, KTM 250 SX, Suzuki RM250, Kawasaki KX250.
Engine Type:
Powerful two-stroke engine renowned for its torque and throttle response.
Suspension:
Advanced Kayaba (KYB) front forks and Monocross rear suspension for superior handling.
Aluminum Frame:
Lightweight and rigid aluminum frame for enhanced agility and rider feedback.
Target Audience:
DIY mechanics, amateur racers, and professional technicians.
Engine:
Complete overhaul, disassembly, assembly, tuning, carburetor, ignition system, cooling system (if applicable, though typically air-cooled for this model).
Transmission:
Clutch, gearbox disassembly, assembly, maintenance, lubrication.
Chassis:
Frame inspection, suspension (front fork, rear shock absorber), steering, swingarm, bearings.
Brakes:
Hydraulic front and rear brake systems, caliper overhaul, master cylinder, bleeding procedures, pad replacement.
Electrical:
Ignition system, lighting, wiring diagrams, troubleshooting electrical faults.
Fuel System:
Fuel tank, fuel lines, carburetor tuning and rebuilding, fuel filter.
Exhaust System:
Pipe inspection, silencer maintenance.
Maintenance:
Regular service checks, lubrication points, filter replacements, chain adjustment, spark plug replacement.
Troubleshooting:
Diagnostic procedures for common performance issues, starting problems, engine misfires, electrical faults.
Repair:
Detailed step-by-step repair instructions for all major components, including engine rebuilds and suspension overhauls.
Disassembly Assembly:
Complete instructions for disassembling and reassembling various motorcycle systems.
Torquing Specifications:
Precise torque values for all critical fasteners.
Diagnostic Capabilities:
Advanced diagnostics for engine performance and electrical systems.
Rebuild Procedures:
Comprehensive instructions for complete engine and transmission rebuilds.
Illustrations:
Detailed diagrams and illustrations supporting each procedure.
Engine Type:
2-stroke, liquid-cooled, reed valve, single-cylinder
Bore X Stroke:
66.4 mm x 72.0 mm
Compression Ratio:
9.3:1 (typical, may vary slightly)
Carburetor:
Keihin PWK38S, single
Ignition:
CDI (Capacitor Discharge Ignition)
Horsepower:
Approximately 50-55 HP (estimated, at crankshaft)
Torque:
High torque output characteristic of 250cc two-strokes.
Fuel Type:
Unleaded gasoline, 91-98 octane recommended
Fuel Mixture:
2-stroke oil mixture (e.g., 32:1 or 40:1, consult manual for exact ratio)
Fuel Tank Capacity:
8.0 Liters (2.1 US gallons)
Oil Change Interval:
Refer to manual for transmission oil change intervals (typically every 10-15 hours of riding).
Air Filter Cleaning:
Frequent cleaning recommended (after every few rides, depending on conditions).
Spark Plug Replacement:
Regular inspection and replacement as needed, depending on riding style and conditions.
Top End Rebuild:
Recommended every 20-40 hours of riding for optimal performance.
Engine Oil:
Yamalube 2-Stroke Racing Oil or equivalent JASO FD, API TC rated.
Coolant:
Not applicable (liquid-cooled engine, but coolant type and capacity are specified in the manual).
Brake Fluid:
DOT 4 Hydraulic Brake Fluid
Carburetor Tuning:
Can be sensitive to altitude and temperature changes; requires precise jetting.
Clutch Wear:
Aggressive riding can lead to premature clutch wear; proper adjustment and fluid maintenance are key.
Suspension Maintenance:
Regular fork seal checks and oil changes are crucial for optimal performance.
Yamaha Legacy:
Yamaha has a long and storied history in motorcycle racing, particularly in motocross, with a reputation for innovation and performance.
Yz Lineage:
The YZ250 has been a dominant force in the 250cc motocross class for decades, consistently evolving with aluminum frames, advanced suspension, and potent two-stroke engines.
Production Era:
The YZ250 has been in continuous production since the late 1970s, with significant updates in the early 2000s including the adoption of an aluminum frame.
Manufacturing Location:
Japan
