Segment:
Performance Motocross/Off-Road Motorcycle
Target Audience:
Motocross racers, off-road enthusiasts, and DIY mechanics seeking in-depth technical information for maintenance and repair.
Competitors:
KTM 250 SX, Honda CR250R (prior to discontinuation), Suzuki RM250 (prior to discontinuation).
Vehicle Appeal:
Renowned for its potent 2-stroke power delivery, agile handling, and competitive performance in its class.
Manual Value Proposition:
Provides essential technical data, repair procedures, and troubleshooting guidance to maintain the YZ250's peak performance and longevity.
Engine:
Detailed breakdown of the 249cc liquid-cooled 2-stroke engine, including top-end (cylinder, piston, rings, reed valve), bottom-end (crankshaft, connecting rod, bearings), cooling system, and lubrication.
Transmission:
5-speed constant mesh transmission, clutch operation, gear inspection, and replacement procedures.
Chassis:
Frame inspection and repair, suspension (front forks and rear shock absorber), steering system, and wheel/tire servicing.
Brakes:
Hydraulic front and rear disc brake systems, caliper maintenance, pad replacement, fluid bleeding, and master cylinder servicing.
Electrical:
Ignition system (CDI, spark plug), lighting, battery, wiring diagrams, and troubleshooting common electrical faults.
Fuel System:
Carburetor (Keihin PWK38S) disassembly, cleaning, adjustment, jetting guidance, fuel tank, and fuel lines.
Exhaust:
Exhaust system components, silencer maintenance, and proper reassembly.
Routine Maintenance:
Oil changes, air filter cleaning/replacement, chain adjustment, spark plug inspection, coolant checks, brake system checks.
Troubleshooting:
Step-by-step diagnostics for common problems such as starting issues, poor performance, overheating, and electrical faults.
Engine Rebuild:
Complete engine disassembly, inspection, overhaul, and reassembly procedures, including torque specifications for all critical fasteners.
Suspension Service:
Fork seal replacement, oil changes, shock absorber servicing, and adjustment procedures.
Carburetor Tuning:
Detailed instructions on carburetor adjustment, jetting recommendations for different riding conditions, and cleaning procedures.
Electrical Diagnosis:
Schematics, component testing, and fault finding for the ignition, lighting, and charging systems.
Depth:
Comprehensive, covering everything from basic owner maintenance to complete engine and chassis rebuilds.
Detail Level:
Highly detailed with exploded diagrams, part numbers, specifications, and step-by-step instructions.
Engine Type:
Liquid-cooled, 2-stroke, Reed valve induction
Bore X Stroke:
66.4 mm x 72.0 mm
Compression Ratio:
8.2:1 (for 2009 model)
Horsepower Estimated:
Approx. 45-50 HP (peak, rider dependent)
Torque Estimated:
Approx. 30-35 lb-ft (peak, rider dependent)
Carburetor:
Keihin PWK38S, flat slide
Fuel Type:
Unleaded gasoline (minimum 91 octane recommended)
Oil Mixture:
50:1 ratio of unleaded gasoline to high-quality 2-stroke synthetic oil (e.g., Yamalube 2-stroke oil).
Ignition System:
Digital CDI (Capacitor Discharge Ignition)
Cooling Method:
Liquid-cooled
Coolant Type:
Yamaha's recommended high-quality antifreeze coolant (50% ethylene glycol and 50% distilled water).
Oil Change Transmission:
Every 10-15 hours of riding or annually, whichever comes first.
Air Filter Cleaning:
Every 5-10 hours of riding or as needed based on dust conditions.
Spark Plug Inspection:
Every 10-15 hours of riding.
Top End Rebuild Recommendation:
Typically every 50-100 hours of aggressive riding, but depends on maintenance and riding style. Manual provides detailed inspection points.
Engine Oil Type:
Yamalube 4-stroke motorcycle oil (API SG, SF, SE) or equivalent. Viscosity: SAE 10W-30.
Coolant Type:
Yamaha's recommended high-quality antifreeze coolant (50% ethylene glycol and 50% distilled water).
Brake Fluid Type:
DOT 3 or DOT 4 hydraulic brake fluid.
Common Wear Items:
Clutch plates, brake pads, chain and sprockets, piston rings, and fork seals are common wear items requiring regular inspection and replacement.
Carburetor Jetting:
Carburetor jetting may require adjustment based on altitude, temperature, and modifications. The manual provides detailed guidance.
Power Valve Maintenance:
The exhaust power valve system requires periodic cleaning and inspection to ensure proper operation.
Heritage:
Yamaha has a long and successful history in motocross and off-road racing, with the YZ line being a cornerstone of their performance offerings.
Yz250 Lineage:
The YZ250 has evolved significantly since its inception, consistently being a top contender in the 250cc 2-stroke class, known for its powerful engine and competitive chassis.
Production Era:
The YZ250 has been in continuous production for decades, with significant updates occurring periodically.
