Segment:
Performance Motocross/Off-Road Motorcycle
Target Audience:
Motocross racers, off-road enthusiasts, and owners seeking detailed maintenance and repair guidance.
Competitors:
Honda CR250R, Kawasaki KX250, Suzuki RM250, KTM 250 EXC.
Engine Type:
Liquid-cooled, 2-stroke, Reed valve, Case-reed induction
Performance Focus:
Yamaha's renowned aggressive power delivery and agile handling.
Chassis Design:
Steel semi-double cradle frame for strength and rigidity.
Usability:
Designed for ease of use with clear language and logical procedure flow.
Engine System:
Comprehensive coverage of the 250cc liquid-cooled two-stroke engine, including disassembly, inspection, assembly, tuning, and component specifications.
Fuel System:
Carburetor service, jetting information, fuel line maintenance, and fuel tank inspection.
Ignition System:
CDI ignition system diagnostics, troubleshooting, and component testing.
Cooling System:
Radiator, hoses, water pump, and thermostat service and maintenance.
Transmission System:
Gearbox disassembly, inspection, clutch service, and gearbox oil specifications.
Suspension System:
Front fork (USD) and rear shock absorber service, including oil changes, seal replacement, and damping adjustments.
Brake System:
Front and rear hydraulic disc brake system maintenance, caliper service, pad replacement, and fluid bleeding procedures.
Electrical System:
Wiring diagrams, lighting system, battery maintenance, and basic troubleshooting for electrical components.
Chassis And Frame:
Frame inspection, steering head bearing service, and general chassis component maintenance.
Wheels And Tires:
Wheel bearing service, spoke tension adjustment, and tire pressure recommendations.
Routine Maintenance:
Pre-ride inspections, oil changes, filter cleaning/replacement, chain adjustment, and spark plug service.
Troubleshooting:
Diagnostic charts for common problems, including engine starting issues, power loss, and braking irregularities.
Engine Rebuild:
Detailed instructions for top-end rebuilds (piston, rings, cylinder) and bottom-end work (crankshaft, bearings).
Suspension Overhaul:
Complete procedures for fork seal replacement, damper rod service, and shock absorber rebuilding.
Clutch Replacement:
Step-by-step guide for clutch plate replacement and adjustment.
Brake Bleeding:
Proper procedures for bleeding air from the hydraulic brake system.
Depth:
Comprehensive, from basic owner maintenance to complete engine and chassis overhauls, suitable for both novice and experienced mechanics.
Engine Type:
Liquid-cooled, 2-stroke, reed valve, single cylinder
Bore X Stroke:
66.4 x 72.0 mm
Carburetor:
Keihin PWK38S, 38mm
Spark Plug Type:
NGK BR9ES
Starter System:
Kick starter
Horsepower Estimate:
~45-50 hp (at crankshaft, estimated)
Torque Estimate:
~30-33 lb-ft (at crankshaft, estimated)
Fuel Type:
Unleaded gasoline (91 octane or higher recommended)
Fuel Mixture:
2-stroke oil mixed with gasoline at 50:1 ratio (Yamalube 2 recommended)
Type:
5-speed constant mesh
Gear Ratios:
Specific gear ratios detailed within the manual (e.g., 1st: 2.667, 2nd: 1.933, 3rd: 1.500, 4th: 1.235, 5th: 1.000)
Clutch Fluid:
N/A (Cable actuated)
Transmission Oil Type:
Yamaha Genuine Gear Oil (or equivalent SAE 80 hypoid gear oil)
Transmission Oil Capacity:
Approx. 0.65 L (0.69 US qt)
Safety Certification:
N/A (Off-road competition vehicle, not street-legal)
Braking System:
Hydraulic disc brakes front and rear for strong stopping power.
Suspension Control:
Adjustable front forks and rear shock for optimized handling and stability.
Frame Construction:
Robust steel frame designed for durability and impact absorption.
Ergonomics:
Designed for rider control and rider-machine connection.
Oil Change Transmission:
Every 15-20 hours of operation or annually.
Air Filter Cleaning:
After every ride or as needed based on conditions.
Spark Plug Check:
Every 5-10 hours of operation.
Chain Lubrication Adjustment:
Every 5-10 hours of operation, or as needed.
Top End Rebuild:
Every 40-60 hours of operation (depending on riding style and conditions).
Suspension Service:
Fork oil change every 20-30 hours; complete fork and shock service every 40-60 hours.
Coolant:
High-quality permanent type ethylene glycol coolant (50% solution with distilled water).
Brake Fluid:
DOT 4 hydraulic brake fluid.
Common Wear Items:
Clutch plates, piston rings, fork seals, chain and sprockets, brake pads.
Carburetor Tuning:
May require jetting adjustments based on altitude and temperature changes.
Clutch Perch Adjustment:
Cable slack adjustment is critical for proper clutch operation.
Yamaha Legacy:
Yamaha has a long-standing history of innovation and success in motocross and off-road racing, with the YZ line being a cornerstone.
Yz250 Lineage:
The YZ250 has been a dominant force in 250cc motocross for decades, evolving significantly with technological advancements in engine performance, suspension, and chassis design.
2002 Updates:
The 2002 model typically featured refinements in suspension settings, minor engine tuning updates, and aesthetic changes compared to previous years.
Production Era:
Early 2000s
Manufacturing Origin:
Japan
Motocross Awards:
The YZ250 line has consistently received accolades and championship wins throughout its production history, widely recognized for its performance.
Performance Ratings:
Consistently rated highly by motorcycle publications for its power, handling, and durability in its class.
Manufacturing Standards:
Manufactured to Yamaha's rigorous quality and performance standards.
