Segment:
High-performance Motocross Competition
Competitor Set:
Honda CRF250R, Kawasaki KX250F, Suzuki RM-Z250, KTM 250 SX-F.
Key Selling Points:
Renowned for its potent four-stroke engine, agile handling, and advanced KYB suspension components, the YZ250F was a top contender in its class.
Engine Layout:
Liquid-cooled, four-stroke, DOHC, four-valve, single-cylinder.
Suspension Tech:
KYB Speed Sensitive System (SSS) forks and KYB shock absorber.
Frame Design:
Aluminum Bilateral Beam frame for optimized rigidity and weight balance.
Primary Coverage:
Factory Repair and Service
Specific Systems:
Engine, Fuel System, Cooling System, Chassis, Suspension, Electrical System, Braking System, Drivetrain
Type:
Factory Service Manual / Repair Manual
Format:
Digital Download (PDF)
Interactivity:
Clickable Chapters
Engine Mechanical:
Complete teardown and rebuild of the 250cc four-stroke engine, including cylinder, piston, crankshaft, connecting rod, valves, camshafts, and lubrication system.
Fuel And Induction:
Carburetor (Mikuni BSR38), fuel delivery, jetting specifications, air filter maintenance, and fuel tank servicing.
Cooling System:
Radiator, hoses, water pump, coolant specifications, and bleeding procedures.
Chassis And Frame:
Frame inspection, sub-frame mounting, footpegs, and general chassis setup.
Suspension Front:
KYB Speed Sensitive System (SSS) front forks, including fork leg disassembly, oil levels, spring rates, damping adjustments, and seal replacement.
Suspension Rear:
KYB shock absorber, linkage system, spring pre-load, damping adjustments, and rebuild procedures.
Braking System:
Front and rear hydraulic disc brake systems, including caliper servicing, master cylinder, brake fluid specifications (DOT 4 recommended), pad replacement, and bleeding.
Drivetrain:
Clutch operation, cable adjustment, gear shift mechanism, and chain maintenance (lubrication and tension).
Electrical System:
Ignition system, spark plug specifications, stator, CDI unit, wiring diagrams, lighting (if applicable), and battery maintenance.
Wheels And Tires:
Spoke tensioning, rim maintenance, tire pressure recommendations, and wheel bearing service.
Maintenance Routine:
Scheduled maintenance tasks, including oil changes, filter replacements, chain adjustments, and general inspection points.
Troubleshooting:
Diagnostic procedures for common issues, symptom identification, and step-by-step repair solutions.
Repair Rebuild:
Detailed instructions for component disassembly, cleaning, inspection, repair, and reassembly of all major motorcycle systems.
Torque Specifications:
Precise torque values for critical fasteners throughout the motorcycle, essential for safe and reliable operation.
Visual Guides:
Includes pictures and diagrams to illustrate procedures and component identification.
Depth:
Comprehensive, covering everything from basic pre-ride checks to full engine and suspension overhauls.
Target Audience:
Professional mechanics, experienced DIY enthusiasts, and dedicated motocross racers.
Type:
Liquid-cooled, four-stroke, DOHC, four-valve, single-cylinder
Bore X Stroke:
77.0 mm x 53.6 mm
Compression Ratio:
13.1:1
Carburetor:
Mikuni BSR38 with accelerator pump
Horsepower Estimate:
Approx. 38-40 HP (at crank, peak)
Torque Estimate:
Approx. 20-22 lb-ft (at crank, peak)
Fuel Type:
Unleaded gasoline (91 octane or higher recommended)
Fuel Tank Capacity:
2.1 gallons (7.9 L)
Crash Test Rating:
N/A (Off-road competition vehicle, not designed for road use or subject to typical road vehicle safety ratings)
Brakes:
Hydraulic disc brakes front and rear for powerful and controlled stopping.
Throttle Control:
Positive throttle response for precise rider input.
Frame Integrity:
Robust aluminum frame designed for durability under extreme conditions.
Ergonomics:
Designed for rider control and stability in competitive riding scenarios.
Engine Oil Change:
Every 10 hours of riding or annually, whichever comes first. More frequently under severe use.
Air Filter Cleaning:
After every 5 hours of riding, or more often in dusty conditions.
Spark Plug Inspection:
Every 10 hours of riding.
Chain Lubrication Adjustment:
Every 5 hours of riding.
Engine Oil:
Yamalube 4 (10W-40) or SAE 10W-40 API SG classification. Oil capacity: 1.10 L (1.16 US qt) without filter change, 1.20 L (1.27 US qt) with filter change.
Coolant:
High-quality engine coolant, 50% mixture with de-ionized water. Capacity: 0.80 L (0.85 US qt).
Brake Fluid:
DOT 4 recommended for hydraulic brake systems.
Carburetor Tuning:
Proper jetting and accelerator pump adjustment can be crucial for optimal performance across various elevations and temperatures. The manual details this extensively.
Suspension Maintenance:
Regular fork seal inspection and oil changes are vital for maintaining the performance of the KYB SSS forks.
Valve Clearance:
Valve clearance checks and adjustments are critical for engine longevity and performance, typically recommended every 20-30 hours of riding.
