Category:
High-performance Motocross Motorcycle
Target Audience:
Enthusiast riders, mechanics, and owners seeking to maintain and repair their YZ250
Competitors 2003:
Honda CR250R, Kawasaki KX250, Suzuki RM250
Performance Focus:
Lightweight, powerful two-stroke engine, agile handling
Value Proposition:
Essential resource for preserving performance, reliability, and resale value
Engine:
Top-end and bottom-end overhaul, carburetor tuning, cooling system, lubrication, ignition system, starting system
Transmission:
Clutch operation and overhaul, gearbox inspection and repair, shift mechanism
Chassis:
Frame inspection, suspension tuning and rebuild (forks and rear shock), steering system
Brakes:
Hydraulic brake system overhaul (front and rear), pad replacement, fluid bleeding
Electrical:
Wiring diagrams, lighting system, ignition coil testing, battery maintenance
Fuel System:
Fuel tank, fuel lines, carburetor (Mikuni VM38, likely), jetting specifications
Cooling System:
Radiator, coolant type, capacity, and bleeding procedures
Maintenance:
Scheduled maintenance intervals, pre-ride checks, cleaning procedures
Troubleshooting:
Diagnostic charts for common problems, symptom-based troubleshooting guides
Repair:
Step-by-step repair instructions for all major components
Rebuild:
Complete engine and transmission rebuild procedures
Adjustment:
Clutch lever free play, throttle cable adjustment, carburetor idle speed
Depth:
Comprehensive: Covers basic maintenance to complete engine disassembly and rebuilding
Diagnostics:
Detailed diagnostic procedures and specifications
Torque Specs:
Includes specific torque values for all critical fasteners
Bore X Stroke:
Approx. 68.0 x 68.0 mm (verify with manual for exact spec)
Compression Ratio:
Approx. 8.6:1 (low end for premium fuel, typical for this era)
Engine Configuration:
Single-cylinder, Liquid-cooled, Reed valve induction, 2-stroke
Power Delivery:
Strong mid-range and top-end power characteristics
Horsepower:
Estimated 40-45 HP (at crankshaft, typical for model year)
Torque:
Estimated 28-32 lb-ft (at crankshaft, typical for model year)
Carburetor:
Mikuni VM38 (typical specification for YZ250 of this era), 38mm
Fuel Type:
Unleaded gasoline (91 octane or higher recommended), 50:1 pre-mix with 2-stroke oil
Oil Mixture:
Yamaha 2-stroke oil (or equivalent premium 2-stroke oil) at 50:1 ratio
Ignition System:
CDI (Capacitor Discharge Ignition)
Length:
Approx. 2165 mm (85.2 in)
Width:
Approx. 825 mm (32.5 in)
Height:
Approx. 1280 mm (50.4 in)
Wheelbase:
Approx. 1465 mm (57.7 in)
Dry Weight:
Approx. 98 kg (216 lbs)
Fuel Tank Capacity:
8.0 liters (2.1 US gal)
Front Suspension Type:
Telescopic, cartridge type, with adjustable compression and rebound damping
Front Suspension Travel:
Approx. 295 mm (11.6 in)
Rear Suspension Type:
Monocross, single shock, with adjustable preload, compression, and rebound damping
Rear Suspension Travel:
Approx. 305 mm (12.0 in)
Front Tire:
80/100-21 M/C 51M
Rear Tire:
110/90-19 M/C 62M
Front Brake:
Hydraulic disc, 250mm diameter
Rear Brake:
Hydraulic disc, 245mm diameter
Oil Change Transmission:
Every 10-15 hours of riding (or as specified in the manual)
Air Filter Cleaning:
After every few rides, or more frequently in dusty conditions
Spark Plug Inspection:
Every 10-15 hours of riding
Top End Rebuild:
Every 40-60 hours of riding (depending on usage and maintenance)
Coolant:
Yamaha الأمثال Blue Antifreeze or equivalent silicate-free, ethylene glycol-based antifreeze (50% solution)
Wear Items:
Piston, piston rings, clutch plates, and bearings are wear items common to high-performance 2-strokes.
Carburetor Tuning:
Carburetor jetting can be sensitive to altitude, temperature, and modifications; proper tuning is crucial for optimal performance.
Suspension Maintenance:
Regular fork seal inspection and oil changes are important for consistent damping performance.
Yamaha Legacy:
Yamaha has a long and successful history in off-road racing, particularly in the motocross and enduro categories.
Yz Lineage:
The YZ250 has been a dominant force in the 250cc two-stroke class for decades, with continuous refinement in engine performance, suspension, and chassis dynamics.
Production Era:
The YZ250 has been in continuous production since the early 1970s, with the 2003 model representing a mature and well-developed iteration of the design.
Manufacturing Location:
Japan
