Segment:
High-performance motocross and off-road competition motorcycle.
Target Audience:
Motocross racers, off-road enthusiasts, and general maintenance users seeking in-depth technical knowledge.
Competitors:
Honda CR250R, Kawasaki KX250, Suzuki RM250.
Engine Type:
Renowned for its potent 2-stroke power delivery and lightweight chassis.
Chassis Design:
Aluminum bilateral beam frame, contributing to agility and handling.
Suspension Advancements:
Industry-leading Kayaba (KYB) Speed Sensitive System (SSS) forks and a refined Monocross rear suspension system for superior damping and adjustability.
Engine:
Complete engine disassembly, assembly, inspection, tuning, and troubleshooting for the 249cc liquid-cooled 2-stroke engine.
Fuel System:
Carburetor (Keihin PWK38S) specifications, adjustment, cleaning, and troubleshooting; fuel tank and lines.
Ignition System:
CDI ignition system, troubleshooting, component testing, and specifications.
Cooling System:
Radiator, hoses, water pump, thermostat, coolant specifications, and bleeding procedures.
Transmission:
6-speed gearbox, clutch assembly (wet multi-plate), maintenance, disassembly, assembly, and lubrication.
Suspension Front:
Inverted telescopic fork (Kayaba), disassembly, assembly, oil change, seal replacement, compression/rebound adjustment, and spring rates.
Suspension Rear:
Monocross suspension, shock absorber, linkage system, bearing maintenance, and adjustment procedures.
Brakes Front:
Hydraulic disc brake system, caliper, master cylinder, brake fluid specifications (DOT 4), pad replacement, bleeding, and rotor inspection.
Brakes Rear:
Hydraulic disc brake system, caliper, master cylinder, brake fluid specifications (DOT 4), pad replacement, bleeding, and rotor inspection.
Wheels And Tires:
Wheel bearing inspection and replacement, spoke tension adjustment, tire pressure recommendations, and wheel alignment checks.
Electrical System:
Wiring diagrams, lighting system, ignition coil, stator, rectifier, and battery maintenance (if applicable for ignition).
Frame And Bodywork:
Frame inspection, subframe, footpegs, fuel tank, seat, fenders, and plastics removal/installation.
Maintenance:
Scheduled maintenance, routine checks, lubrication points, and cleaning procedures.
Troubleshooting:
Diagnostic charts for common problems, symptoms, causes, and corrective actions.
Repair:
Detailed step-by-step instructions for component repair and replacement.
Rebuilds:
Engine and transmission rebuild procedures, including torque specifications and critical measurements.
Adjustments:
Carburetor jetting, ignition timing, clutch play, suspension settings, and throttle cable adjustment.
Depth:
Comprehensive, suitable for professional mechanics and experienced DIY enthusiasts. Covers everything from basic maintenance to full engine and chassis overhauls.
Engine Type:
2-stroke, liquid-cooled, reed valve induction, YPVS (Yamaha Power Valve System)
Bore X Stroke:
66.4 mm x 72.0 mm
Compression Ratio:
8.8:1 (typical, may vary slightly by year)
Horsepower:
Approx. 45-50 HP (at crankshaft, manufacturer claims vary)
Torque:
Approx. 27-30 lb-ft (at crankshaft, manufacturer claims vary)
Carburetor:
Keihin PWK38S, CDI controlled YPVS
Fuel Type:
Unleaded gasoline (91 octane or higher recommended)
Oil Mixture:
Yamalube 2R or equivalent 2-stroke oil, pre-mix ratio 50:1 (gasoline:oil)
Transmission Type:
Constant mesh, 6-speed
Clutch Type:
Wet, multi-plate
Gear Ratios:
Refer to manual for specific year/model gear ratios. Typically includes: 1st: 2.615, 2nd: 1.933, 3rd: 1.556, 4th: 1.333, 5th: 1.182, 6th: 1.000
Final Drive:
Chain drive, 520 O-ring type
Transmission Oil Type:
Yamalube Gear Oil 10W-30 or equivalent API SE, SF, SG type.
Transmission Oil Capacity:
0.75 L (0.79 US qt)
Oil Change Transmission:
Every 10-15 hours of riding or annually. Refer to manual for detailed recommendations.
Air Filter Cleaning:
After every few rides or as needed depending on conditions.
Spark Plug Inspection:
Every 10-15 hours of riding.
Brake Fluid Flush:
Every 12 months or as per manual recommendations.
Suspension Service:
Fork oil change every 20-30 hours; rear shock service as needed or per manual.
Engine Oil Premix:
Yamalube 2R or equivalent 2-stroke racing oil (50:1 ratio)
Transmission Oil:
Yamalube Gear Oil 10W-30 or equivalent API SE, SF, SG
Coolant:
Yamaha All Weather Motor Oil (liquid cooled) or equivalent permanent type anti-freeze coolant (50% mixture)
Clutch Wear:
Can experience rapid clutch wear with aggressive use; proper adjustment and timely replacement of plates and springs are crucial.
Power Valve Sticking:
YPVS mechanism can accumulate carbon and stick if not regularly cleaned and serviced, affecting powerband.
Suspension Seals:
Fork and shock seals can degrade over time and require replacement to prevent oil leaks.
Carburetor Tuning:
Requires precise jetting and adjustment based on altitude, temperature, and riding style for optimal performance.
Yamaha Legacy:
Yamaha has a long and successful history in motocross and off-road racing, consistently producing competitive and innovative machinery.
Yz250 Lineage:
The YZ250 has been a dominant force in the 250cc 2-stroke class for decades, undergoing continuous refinement and updates.
02-08 Updates:
This generation saw significant updates including revised suspension (Kayaba SSS forks), updated styling, chassis refinements, and engine tuning improvements to maintain its competitive edge.
Manufacturing Location:
Japan
Significance:
The YZ250 remains a popular choice for riders who prefer the simplicity, power, and engaging nature of a 2-stroke engine.
