Segment:
Motocross Competition
Target Audience:
Motocross racers, off-road enthusiasts, and mechanics performing maintenance and repairs on the Yamaha YZ250.
Key Competitors Era:
Honda CR250R, Kawasaki KX250, Suzuki RM250.
Yz Legacy:
The YZ250 has a long-standing reputation for performance, reliability, and competitive success in motocross. The 1998 model represented a significant evolution in Yamaha's 250cc two-stroke offering.
Manual Value Proposition:
Provides essential, in-depth technical information to maintain and repair the 1998 Yamaha YZ250, enabling owners to keep their bike in peak condition for performance and longevity.
Primary Coverage:
1998 Yamaha YZ250
Secondary Coverage Notes:
Will work with similar years and models, specifically referencing 1982 YZ250 as an example of related coverage.
Estimated Pages:
300-500 (typical for comprehensive service manuals of this era)
Type:
Complete Service Repair Workshop Manual
Format:
Digital (likely PDF, based on common sales practices for older manuals)
Engine:
Complete engine overhaul, top-end rebuild (piston, rings, cylinder), bottom-end (crankshaft, bearings, seals), lubrication, cooling (if applicable, though YZ250 is air-cooled), fuel system (carburetor tuning, disassembly, cleaning), ignition system (CDI, spark plug, timing).
Transmission:
Clutch operation and adjustment, gearbox disassembly and reassembly, gear inspection, shift mechanism, transmission fluid specifications and change intervals.
Chassis:
Frame inspection and repair, suspension (forks - disassembly, seal replacement, oil levels/viscosity, valving; rear shock - service, linkage bearings), steering system (headset bearings), wheel and tire maintenance, spoke tensioning.
Brakes:
Front and rear brake system service (hydraulic - caliper disassembly, piston seals, fluid flush and bleeding, master cylinder rebuild), brake pad replacement, rotor inspection.
Electrical:
Wiring diagrams, lighting system, ignition system components, troubleshooting electrical faults, battery maintenance (if applicable, though often kick-start only).
Bodywork And Controls:
Handlebar replacement, control cable adjustment and replacement (throttle, clutch), seat removal, body panel (fenders, shrouds) mounting and removal.
Maintenance:
Regular scheduled maintenance, pre-ride checks, post-race cleaning and inspection, chain lubrication and adjustment, air filter cleaning and oiling, spark plug replacement, coolant checks (for radiators on some models), brake bleeding.
Repair:
Complete engine rebuild, transmission overhauls, suspension component repair and replacement, brake system repairs, carburetor rebuilding, electrical system troubleshooting and repair.
Troubleshooting:
Diagnostic flowcharts and symptom-based troubleshooting for common issues related to starting, running, power loss, and component failures.
Technical Data:
Torque specifications for all fasteners, clearance measurements, timing settings, fluid capacities, diagnostic readings.
Depth:
Comprehensive. Covers everything from basic fluid checks and adjustments to complete engine disassembly, rebuilding, and performance tuning.
Digital Format:
Likely PDF. Optimized for viewing on computers and tablets, with searchable text capabilities if the source was well-scanned or produced digitally.
Printability:
Designed to be printable. High-resolution images and clear text ensure legibility when printed.
Binding:
Not applicable for digital format, but original printed manuals were typically perfect bound or spiral bound for lay-flat usability in a workshop.
Paper Type:
Not applicable for digital format, but original manuals were printed on durable, often glossy or semi-gloss paper to withstand workshop environments.
Engine Configuration:
Single-cylinder, 2-stroke, reed valve induction
Bore X Stroke:
68.0 mm x 68.6 mm (typical for YZ250 of this era)
Compression Ratio:
8.4:1 (static, typical for 1998 model)
Cooling System:
Liquid-cooled (radiators)
Ignition:
CDI (Capacitor Discharge Ignition)
Horsepower:
Approx. 48-50 HP @ 7500 RPM (estimated)
Torque:
Approx. 32-34 lb-ft @ 6500 RPM (estimated)
Carburetor Model:
Keihin PWK38 (typical)
Fuel Type:
Unleaded gasoline (91-98 octane recommended) mixed with 2-stroke oil
Premix Ratio:
50:1 (Yamalube 2R or equivalent high-quality 2-stroke oil)
Type:
5-speed constant mesh
Clutch Type:
Wet, multi-plate, cable-actuated
Gear Ratios:
Specific gear ratios available in the manual (e.g., 1st: 32/15, 2nd: 28/17, 3rd: 25/19, 4th: 23/20, 5th: 20/22)
Transmission Oil Type:
Yamaha Genuine Gear Oil 10W-30 or equivalent SAE 80W transmission oil.
Transmission Oil Capacity:
Approximately 0.8 Liters (0.85 US qt)
Motocross Design:
Designed for off-road competition, safety features are primarily related to vehicle stability and control under racing conditions, not road-legal safety standards.
Braking System:
Hydraulic disc brakes front and rear for superior stopping power.
Suspension Performance:
Long-travel, adjustable suspension (Kayaba forks and shock) designed to absorb impacts and maintain tire contact for control.
Chassis Stiffness:
Durable aluminum frame provides rigidity and predictable handling.
Oil Change:
Transmission oil: Every 10-15 hours of riding or annually.
Air Filter:
Clean and re-oil after every 5-10 hours of riding, or more frequently in dusty conditions.
Spark Plug:
Inspect and clean/gap every 10-15 hours; replace every 20-30 hours or as needed.
Top End Rebuild:
Piston and rings: Every 20-40 hours of racing or per manual's specific recommendations for optimal performance.
Chain And Sprockets:
Lubricate chain every 5-10 hours; adjust tension as needed per manual's specifications; inspect sprockets for wear.
Coolant:
Ethylene glycol-based coolant (50% coolant, 50% distilled water recommended).
Brake Fluid:
DOT 3 or DOT 4 hydraulic brake fluid.
Ypvs System:
Yamaha Power Valve System (YPVS) can sometimes accumulate carbon buildup, leading to sticking or erratic operation. Requires periodic cleaning and inspection as detailed in the manual.
Clutch Slippage:
Can occur with aggressive riding or if clutch plates are worn beyond service limits. Manual details inspection and replacement procedures.
Carburetor Tuning:
Proper jetting is crucial for two-stroke performance and can be sensitive to altitude and temperature changes. The manual provides detailed carburetor tuning information.
Yamaha Motorcycles:
Yamaha has a long and successful history in motorcycle racing, particularly with their two-stroke 'YZ' line, which has been a dominant force in motocross for decades.
Yz250 Development:
The YZ250 underwent continuous development throughout the 1980s and 1990s, with the 1998 model benefiting from advancements in engine technology (like YPVS - Yamaha Power Valve System), suspension, and chassis design.
Production Years:
The YZ250 has been in continuous production in various forms since 1974.
Motocross Performance:
The YZ250 line consistently received praise and accolades for its competitive performance throughout its production years, often cited for its potent engine and agile handling in motocross magazines and reviews.
Engine Power Delivery:
Highly rated for its strong mid-range and top-end power, characteristic of competitive 250cc two-strokes of the era.
Not Applicable:
As a competition-only vehicle, it is not subject to road-legal safety certifications.
