Segment:
High-performance Motocross/Off-road competition motorcycle.
Target Audience:
Competitive motocross riders, off-road enthusiasts, and owners seeking to maintain and repair their YZ250LC.
Competitors 2003:
KTM 250 SX, Honda CR250R, Suzuki RM250, Kawasaki KX250.
Performance Focus:
Renowned for its potent two-stroke engine, agile handling, and competitive motocross performance.
Design Philosophy:
Yamaha's 'Cylinder Reed Valve' (CRV) engine technology and 'Long-Travel Suspension' (LTS) systems for optimized off-road capability.
Engine:
Complete engine overhaul, tuning, diagnostics, and repair procedures.
Transmission:
Clutch, gearbox, shifting mechanism, and related components.
Suspension:
Front forks (KYB Speed-Sensitive System), rear shock absorber (Monocross), tuning, and seal replacement.
Brakes:
Front and rear hydraulic disc brakes, caliper service, master cylinder overhaul, fluid bleeding.
Electrical System:
Ignition system, lighting, CDI unit, wiring diagrams, troubleshooting electrical faults.
Fuel System:
Carburetor (Keihin PWK 38), fuel tank, fuel lines, jetting information.
Cooling System:
Liquid-cooled system, radiator, water pump, thermostat, coolant specifications.
Exhaust System:
Expansion chamber, muffler, repacking procedures.
Frame And Bodywork:
Frame inspection, subframe, fuel tank, seat, plastics, handlebars, controls.
Wheels And Tires:
Wheel bearing service, spoke tensioning, tire fitment, recommended pressures.
Troubleshooting:
Diagnostic flowcharts for common performance issues, starting problems, and noises.
Estimated Pages:
Over 300 pages (typical for a comprehensive service manual).
Type:
Official Factory Service Repair Manual
All Systems:
Covers all major mechanical, electrical, and chassis systems of the 2003 Yamaha YZ250LC.
Maintenance Tasks:
Routine maintenance, oil changes, filter replacements, chain adjustment, bolt torque checks.
Repair Procedures:
Detailed step-by-step instructions for engine rebuilding, suspension servicing, brake caliper repair, electrical component replacement.
Diagnostic Procedures:
Troubleshooting guides for identifying and rectifying common and uncommon issues.
Assembly Disassembly:
Comprehensive breakdown and reassembly instructions for all major components.
Depth:
Provides in-depth technical information suitable for both home mechanics and professional technicians, including torque specifications, clearances, and detailed diagrams.
Format Details:
Searchable PDF, allowing for quick text-based searches of specific terms and procedures. High-resolution scanned pages for clarity.
Quality:
High-resolution digital reproduction of the original factory manual, ensuring clear diagrams and text.
Binding:
N/A (Digital PDF Download)
Paper:
N/A (Digital PDF Download)
Type:
2-stroke, liquid-cooled, reed-valve inducted, single cylinder
Bore X Stroke:
66.4 mm x 72.0 mm
Compression Ratio:
8.2:1 (typical, may vary slightly)
Cylinder Head:
Yamaha Power Valve System (YPVS)
Horsepower Est:
Approx. 45-50 HP (at crankshaft)
Torque Est:
Approx. 30-33 lb-ft (at crankshaft)
Carburetor:
Keihin PWK38S, dual-circuit
Fuel Type:
Unleaded gasoline, 91-98 octane recommended
Oil Mixture:
Yamalube 2-stroke oil at 50:1 ratio (check manual for specific recommendations).
Coolant Capacity:
0.95 L (1.0 US qt)
Coolant Type:
Ethylene glycol-based coolant with demineralized water (50:50 mix recommended).
Type:
5-speed constant mesh
Clutch Type:
Wet, multiple-disc
Gear Ratios:
1st: 2.615, 2nd: 1.933, 3rd: 1.555, 4th: 1.291, 5th: 1.043
Final Drive:
Chain drive, 13/50 tooth sprockets (standard).
Clutch Adjustment:
Cable-operated, with adjustable levers and cable tension.
Oil Change:
Every 10-15 hours of riding (or as specified in the manual for optimal performance).
Air Filter Cleaning:
Clean after every few rides, especially in dusty conditions.
Spark Plug Replacement:
Every 20-30 hours of riding, depending on usage and plug condition.
Top End Rebuild:
Recommended every 40-60 hours of hard riding (piston, rings, cylinder inspection).
Transmission Oil Type:
Yamaha Gear Oil Hypoid 80W-90 or equivalent API GL-4 specification.
Transmission Oil Capacity:
1.10 L (1.16 US qt)
Brake Fluid Type:
DOT 4 hydraulic brake fluid (ensure it's fresh).
Power Valve Sticking:
YPVS system can accumulate carbon deposits and stick if not regularly cleaned and maintained, affecting performance.
Clutch Wear:
Clutch plates can wear over time, especially with aggressive riding, leading to slipping.
Carburetor Jetting:
Proper jetting is critical for optimal performance in varying altitudes and temperatures; manual provides baseline settings.
Yamaha Legacy:
Yamaha has a long and storied history in motocross and off-road racing, with the YZ line being a cornerstone of their performance offerings for decades.
Yz250 Lineage:
The YZ250 has evolved significantly since its inception, with continuous improvements in engine technology, suspension, and chassis design. The 2003 model represents a refinement of the platform that has proven successful in competition.
Production Era:
The YZ250LC was part of the 'LC' (Liquid Cooled) generation of Yamaha's two-stroke motocross bikes.
