Category:
Performance Motocross / Off-Road Motorcycle
Competitors 1988:
Honda CR250R, Kawasaki KX250, Suzuki RM250, KTM 250 EXC.
Yz250 1988 Highlights:
Known for its strong engine performance, robust suspension (often KYB or Showa components), and competitive chassis. This era represented significant advancements in motocross technology, with Yamaha often leading in engine tuning and suspension design.
Engine:
Complete engine overhaul, disassembly, inspection, assembly, tuning, carburetor, cooling system (if applicable).
Transmission:
Gearbox disassembly, inspection, assembly, clutch, shift mechanism.
Suspension:
Front forks (KYB/Showa type for the era), rear monoshock, linkage, damping adjustments, seal replacement, fluid changes.
Brakes:
Front and rear hydraulic disc brake systems, caliper overhaul, master cylinder, brake fluid, pad replacement, bleeding procedures.
Electrical:
Ignition system, lighting, charging system (stator, CDI), wiring diagrams, troubleshooting common electrical faults.
Chassis And Bodywork:
Frame inspection, fuel tank, seat, fenders, handlebars, footpegs, bearing checks.
Wheels And Tires:
Wheel bearing maintenance, spoke tensioning, tire selection and mounting, rim specifications.
Maintenance:
Scheduled maintenance, oil changes, filter replacements, chain adjustment, spark plug replacement, lubrication points.
Troubleshooting:
Diagnostic procedures for common performance issues, starting problems, overheating, and component failures.
Repair:
Step-by-step instructions for component removal, repair, and reinstallation for all major systems.
Technical Specifications:
Torque specifications, clearances, fluid capacities, and other critical data for accurate servicing.
Depth:
Comprehensive, covering everything from routine maintenance to full engine and transmission rebuilds, including advanced diagnostics and electrical system troubleshooting.
Resolution:
High-resolution scans of original factory documentation, ensuring clarity of text and diagrams.
Binding:
Not applicable for digital format. Original manuals were typically bound paper publications.
Paper Quality:
Not applicable for digital format. Original manuals used durable, coated paper suitable for workshop environments.
Engine Type:
Liquid-cooled, 2-stroke, single-cylinder
Displacement:
249 cc (249cc)
Bore X Stroke:
Approx. 68.0 mm x 68.6 mm (specific factory spec likely in manual)
Compression Ratio:
Typically around 7.0:1 to 7.5:1 for this model year and class (manual will confirm exact)
Horsepower Estimated:
Approx. 40-45 HP (at crankshaft, specific dyno data varies, manual will provide official)
Torque Estimated:
Approx. 25-28 lb-ft (at crankshaft, specific dyno data varies, manual will provide official)
Carburetor:
Mikuni VM Series (likely 34mm or 36mm, manual will specify exact model and jetting).
Fuel Type:
Unleaded gasoline (91 octane or higher recommended, pre-mix oil required)
Fuel Mixture:
2-stroke pre-mix oil, typically 20:1 or 32:1 ratio (manual will specify exact).
Ignition System:
CDI (Capacitor Discharge Ignition)
Cooling System:
Liquid-cooled
Coolant Type:
Ethylene glycol-based coolant mixture (manual will specify ratio and capacity).
Transmission Type:
Constant-mesh 6-speed manual
Clutch Type:
Wet, multi-plate
Gear Ratios:
Specific ratios will be detailed in the manual, crucial for engine tuning and performance.
Transmission Oil Type:
API GL-4, SAE 80 or 10W-30 gear oil (manual will specify exact, crucial for proper lubrication).
Transmission Oil Capacity:
Approx. 1.0 - 1.2 liters (manual will confirm exact).
Overall Length:
Typical for its class, around 2150-2200 mm (manual will provide exact)
Overall Width:
Typical for its class, around 800-850 mm (manual will provide exact)
Overall Height:
Typical for its class, around 1250-1300 mm (manual will provide exact)
Dry Weight:
Approx. 99-105 kg (manual will confirm exact)
Fuel Tank Capacity:
Approx. 8.0 - 9.0 liters (manual will confirm exact)
Front Tire Size:
Commonly 80/100-21 (manual will confirm exact)
Rear Tire Size:
Commonly 110/90-18 or 100/90-18 (manual will confirm exact)
Front Suspension Travel:
Approx. 280-300 mm (manual will confirm exact)
Rear Suspension Travel:
Approx. 290-310 mm (manual will confirm exact)
Safety Standards:
N/A (Motocross bikes are not subjected to the same road safety ratings as street vehicles; emphasis is on rider protection and mechanical integrity).
Braking System:
Hydraulic disc brakes front and rear for strong, reliable stopping power.
Frame Construction:
Strong steel frame designed for rigidity and impact resistance in demanding off-road conditions.
Oil Change Transmission:
Every 10-15 hours of riding or as specified in the manual for optimal lubrication.
Air Filter Cleaning:
After every few rides, or more frequently in dusty conditions.
Spark Plug Replacement:
Every 20-40 hours of riding, or when fouling is evident.
Piston Ring Inspection Replacement:
Typically every 40-60 hours for aggressive riding, or based on compression readings.
Top End Rebuild:
Recommended every 60-100 hours of hard use, or sooner if performance degrades. Manual will detail specific checks.
Engine Oil Premix:
Yamalube 2R or equivalent high-quality 2-stroke racing oil, mixed at a ratio specified in the manual (e.g., 20:1 or 32:1).
Brake Fluid:
DOT 3 or DOT 4 hydraulic brake fluid (manual will specify exact type).
Coolant Type:
Permanent type antifreeze coolant (ethylene glycol base), mixed 50/50 with distilled water. (Manual will specify).
Common Wear Items:
Clutch plates, piston rings, reed valves, fork seals, wheel bearings, chain and sprockets. These are typical for a 2-stroke dirt bike of this age and intended use.
Engine Tuning:
Proper jetting and timing are critical for optimal performance and longevity. The manual provides factory specifications for various conditions.
Suspension Maintenance:
Regular fork seal and bushing replacement, as well as rear shock service, is crucial for maintaining handling characteristics.
Yamaha Motorsports Legacy:
Yamaha has a long and storied history in motorsports, particularly in motocross and Grand Prix racing, consistently developing high-performance machines.
Yz Series Development:
The YZ series has undergone continuous development since its inception, with the 1988 model representing a significant iteration incorporating technological advancements from previous years and competitive insights. Key developments around this era included improved suspension technology (like the introduction of USD forks on some models in subsequent years) and engine tuning for increased power and broader powerbands.
Manufacturing Location:
Japan (typically).
