Market Segment:
High-performance motocross/off-road motorcycle
Key Competitors:
Honda CR250R, Kawasaki KX250, KTM 250 SX
Vehicle Focus:
Yamaha's YZ series is renowned for its potent two-stroke engines, capable chassis, and competitive edge in MX racing.
Manual Value Proposition:
Essential resource for owners seeking to maintain, repair, and optimize their 2003 YZ250, ensuring longevity and peak performance.
Coverage Scope:
Complete repair and maintenance
Manual Type:
Factory Service Manual / Repair Manual
Format:
Digital Download (likely PDF)
Navigation Features:
Clickable chapters, internal linking (indicated by 'i......')
Engine System:
Complete engine tear down and rebuild, including cylinder, piston, crankshaft, connecting rod, clutch, transmission, lubrication, cooling, and ignition systems.
Chassis System:
Frame, suspension (front and rear forks, shock absorber), steering, wheels, tires, and braking systems.
Electrical System:
Ignition system, lighting, wiring diagrams, and basic electrical component troubleshooting.
Bodywork Coverage:
Plastics, seat, fuel tank, and general body panel removal and installation procedures.
Maintenance Procedures:
Regular servicing, pre-ride inspections, oil changes, filter replacements, spark plug checks, chain maintenance, and general upkeep.
Repair Procedures:
Detailed step-by-step instructions for disassembly, repair, and reassembly of all major components.
Troubleshooting Procedures:
Diagnostic guides for identifying and resolving common performance issues and failures.
Technical Depth:
Comprehensive, from basic maintenance to complete engine and chassis overhauls.
Detail Level:
Includes detailed illustrations, exploded views, part diagrams, and torque specifications.
Engine Type:
2-stroke, single-cylinder, liquid-cooled
Bore X Stroke:
66.4 mm x 72.0 mm
Compression Ratio:
8.1:1 (typical for this era, manual to confirm)
Intake System:
Reed valve, YPVS (Yamaha Power Valve System)
Horsepower Estimate:
Approx. 45-50 HP (at crankshaft, varies with tuning)
Torque Estimate:
Approx. 28-30 lb-ft (at crankshaft, varies)
Carburetor:
Keihin PWK38, Single
Fuel Type:
Unleaded gasoline (91 octane or higher recommended)
Fuel Oil Mix:
50:1 ratio (premix) with high-quality 2-stroke oil (manual will specify).
Ignition System:
CDI (Capacitor Discharge Ignition)
Transmission Type:
5-speed constant mesh
Clutch:
Wet, multiple-disc
Gear Ratios:
Specific ratios available in manual (e.g., 1st: 2.615, 2nd: 1.857, 3rd: 1.333, 4th: 1.111, 5th: 0.917)
Final Drive:
Chain drive, sealed O-ring type
Oil Change Frequency:
As per manual recommendations, typically after specific riding hours or events.
Air Filter Cleaning:
Regular cleaning and re-oiling after each significant riding session or race.
Spark Plug Inspection:
Regular inspection for wear and proper gap, typically every few hours of use.
Chain And Sprockets:
Regular cleaning, lubrication, and adjustment; inspection for wear.
Coolant Type:
High-quality, permanent type ethylene glycol-based coolant, mixed 50/50 with distilled water. (Manual to specify Yamaha's recommendation).
Transmission Oil Type:
Yamalube Hypoid Gear Oil SAE 80W-90 or equivalent (manual to confirm exact specification and capacity).
Brake Fluid Type:
DOT 3 or DOT 4 hydraulic brake fluid.
Common Yz250 Issues:
Clutch wear, carburetor jetting sensitivity to altitude/temperature, power valve cleaning, suspension seal leaks (general for the era, manual provides specifics).
Valve Clearance:
N/A (2-stroke engine)
Tire Pressure Front:
Refer to manual for specific conditions (e.g., 18-20 PSI for general MX).
Tire Pressure Rear:
Refer to manual for specific conditions (e.g., 12-16 PSI for general MX).
Wheel Bolt Pattern:
N/A (Spoked wheels with axle nuts)
Yamaha Motorcycles:
Yamaha Motor Company is a leading Japanese manufacturer with a rich history in motorcycles, particularly in racing and performance.
Yz Series Legacy:
The YZ250 has been a dominant force in motocross for decades, evolving through various chassis and engine updates, maintaining its two-stroke identity.
Model Production Era:
The YZ250 has been in continuous production for many years, with the 2003 model representing a specific generation of its development.
