Segment:
Performance Motocross Competition
Target User:
Motocross riders, mechanics, and enthusiasts looking for in-depth maintenance and repair knowledge.
Key Competitors Era:
Honda CR250R, Kawasaki KX250, Suzuki RM250
Documentation Type:
Factory original documentation ensuring accuracy and completeness.
Resource Value:
Essential for maintaining peak performance and extending the lifespan of the YZ250.
Primary Focus:
Complete Repair and Maintenance
Specific Sections Covered:
Engine, Transmission, Chassis, Electrical System, Fuel System, Suspension, Brakes, Cooling System, Bodywork, Troubleshooting
Type:
Factory Service Manual / Repair Manual
Format:
Digital Download (PDF)
Navigation:
Clickable Chapters
Engine Internal:
Complete disassembly, inspection, and reassembly of the two-stroke engine.
Transmission And Clutch:
Detailed procedures for clutch inspection, adjustment, and removal/installation; transmission gear inspection and service.
Fuel And Ignition System:
Carburetor tuning and disassembly, ignition system troubleshooting, spark plug specifications.
Suspension Front:
Fork disassembly, seal replacement, oil level and type specifications, internal component inspection.
Suspension Rear:
Monoshock system service, linkage bearing inspection, shock absorber servicing and specifications.
Braking System:
Front and rear brake caliper service, master cylinder overhaul, brake fluid specifications, pad replacement.
Cooling System:
Radiator inspection, coolant type and capacity specifications.
Electrical System:
Wiring diagrams, lighting system service, ignition coil testing, stator/rotor inspection.
Chassis And Frame:
Steering bearing service, wheel bearing inspection, general chassis component checks.
Bodywork And Plastics:
Panel removal and installation procedures.
Routine Maintenance:
Oil changes, chain adjustment, air filter cleaning/replacement, spark plug inspection.
Major Overhaul:
Complete engine teardown and rebuild procedures.
Troubleshooting:
Diagnostic guides for common problems, symptom-based troubleshooting flowcharts.
Rebuilds:
Detailed instructions for cylinder head, piston, crankshaft, and transmission rebuilds.
Adjustments:
Carburetor jetting, clutch cable, throttle cable, and suspension adjustments.
Inspection And Wear Limits:
Specifications for component wear, clearances, and tolerances.
Diagnostic Capabilities:
Advanced diagnostic procedures for electrical and mechanical systems.
Repair Scope:
Comprehensive repair instructions suitable for both home mechanics and professional technicians.
Visual Aids:
Includes high-quality pictures and detailed part diagrams to illustrate procedures.
Searchability:
Likely text-searchable for quick information retrieval.
Image Resolution:
High resolution, suitable for clear viewing of diagrams and images.
Binding For Digital:
N/A (Digital Product)
Paper For Printed Version Analogue:
High-quality, durable paper (typical for factory manuals).
Engine Displacement:
249 cc
Engine Configuration:
Single Cylinder, Liquid-Cooled, Two-Stroke
Bore X Stroke:
66.4 mm x 72 mm
Reed Valve System:
Yes (likely YPVS - Yamaha Power Valve System)
Horsepower Est Peak:
Approx. 45-50 HP (at crankshaft)
Torque Est Peak:
Approx. 30-33 lb-ft (at crankshaft)
Carburetor Model:
Mikuni TMX Series (e.g., TM38)
Fuel Type:
Unleaded Gasoline (91+ octane recommended)
Fuel Oil Mixture:
50:1 ratio (Yamalube 2 or equivalent recommended)
Fuel Tank Capacity:
Approx. 8.0 Liters (1.76 US gallons)
Transmission Type:
5-Speed Constant Mesh
Clutch Type:
Wet, Multi-plate
Gear Ratios:
Specific ratios are detailed within the manual.
Transmission Fluid Type:
Yamaha Gear Oil, SAE 10W-30 (or equivalent API GL-4)
Transmission Fluid Capacity:
Approx. 0.8 Liters (0.85 US quarts)
Overall Length:
Approx. 2,165 mm (85.2 in)
Overall Width:
Approx. 825 mm (32.5 in)
Overall Height:
Approx. 1,260 mm (49.6 in)
Wheelbase:
Approx. 1,475 mm (58.1 in)
Ground Clearance:
Approx. 335 mm (13.2 in)
Dry Weight:
Approx. 101 kg (222.7 lbs)
Wet Weight Est:
Approx. 109 kg (240 lbs) (with all fluids)
Seat Height:
Approx. 970 mm (38.2 in)
Safety Ratings Motorcycle:
N/A (Motorcycles are not typically rated by agencies like NHTSA)
Braking System Type:
Hydraulic Disc, Front and Rear
Suspension System:
Long-travel, adjustable suspension for off-road terrain control.
Frame Construction:
Durable steel or aluminum alloy frame designed for rigidity and impact resistance.
Chain Lubrication Frequency:
Every ride, or every 50-100 miles in dry conditions.
Air Filter Cleaning Frequency:
After every few rides, or more frequently in dusty conditions.
Spark Plug Inspection:
Every 10-15 hours of riding.
Engine Oil Change Interval:
N/A (Two-stroke, premix fuel)
Coolant Type:
Yamaha Coolant (50% ethylene glycol and 50% deionized water)
Fork Oil Type:
Yamalube SAE 0W or SAE 5W Fork Oil (Specific weight detailed in manual)
Brake Fluid Type:
DOT 4 Hydraulic Brake Fluid
Common Wear Items:
Clutch plates, piston rings, spokes, wheel bearings, steering head bearings.
Ypvs System Maintenance:
Can accumulate carbon and require cleaning for optimal performance. The manual details its disassembly and cleaning.
Carburetor Jetting Sensitivity:
Two-stroke carburetors are sensitive to altitude and temperature changes, requiring re-jetting for optimal performance. The manual provides jetting guidelines.
Yamaha Motorcycles:
Yamaha Motor Company, established in 1955, has a long and storied history in motorsports, particularly in off-road racing.
Yz Series Development:
The YZ line has been a dominant force in motocross for decades, with continuous development in engine technology, suspension, and chassis design.
1998 Yz250 Context:
The 1998 model represented Yamaha's ongoing commitment to the 250cc two-stroke class, often featuring refinements based on racing feedback.
Manufacturing Origin:
Japan
