Segment:
Motocross / Off-Road Competition
Competitors 1992:
Honda CR250R, Kawasaki KX250, Suzuki RM250
Engine Type:
Powerful two-stroke, liquid-cooled single-cylinder.
Suspension Frontend:
Long-travel, adjustable inverted front forks.
Suspension Backend:
Monocross rear suspension with adjustable shock.
Brakes:
Powerful hydraulic disc brakes front and rear.
Usefulness:
Essential for owners seeking to perform maintenance, repairs, and optimize performance.
Value Proposition:
Provides authoritative, factory-backed guidance to keep the YZ250 in peak racing condition.
Engine:
Complete engine disassembly, assembly, tuning, troubleshooting, specifications.
Transmission:
Clutch, gearbox, shifting mechanisms, lubrication, maintenance.
Suspension:
Front forks (KYB or similar), rear shock absorber, linkage system, adjustments, rebuild procedures.
Brakes:
Front and rear hydraulic disc brake systems, caliper maintenance, bleeding procedures, master cylinder.
Electrical:
Ignition system, lighting, charging system, wiring diagrams, component testing.
Fuel System:
Carburetor (likely Mikuni VM series), fuel tank, fuel lines, cleaning, jetting, tuning.
Cooling System:
Liquid-cooled system, radiator, hoses, water pump, coolant specifications.
Exhaust System:
Expansion chamber, silencer, maintenance and inspection.
Frame And Bodywork:
Chassis inspection, component removal/installation, plastics, seat.
Maintenance:
Scheduled maintenance, routine checks, lubrication points, filter replacements.
Troubleshooting:
Diagnosis of common problems, symptom-based troubleshooting guides.
Repair:
Detailed step-by-step repair instructions for all major components.
Rebuilds:
Complete engine rebuild procedures, including piston, rings, crankshaft, and cylinder.
Adjustments:
Carburetor tuning, suspension adjustments, clutch and brake lever adjustments.
Diagnostics:
Electrical system diagnostics, compression testing, ignition timing.
Depth:
Full factory-level repair and maintenance information.
Detail Level:
Includes torque specifications, clearances, tolerances, and detailed diagrams.
Engine Type:
2-Stroke, Liquid-Cooled, Reed Valve, Single Cylinder
Displacement:
249 cc (15.2 cu. in.)
Bore X Stroke:
67.0 mm x 70.0 mm (2.64 in x 2.76 in)
Compression Ratio:
8.7:1 (approx.)
Power Valve System:
Yamaha Power Valve System (YPVS)
Horsepower Est:
Approx. 45-50 HP (at crankshaft, varies with tuning)
Torque Est:
Approx. 30-33 lb-ft (at crankshaft, varies with tuning)
Carburetor Type:
Mikuni VM38 (likely) or similar
Fuel Type:
Unleaded gasoline with proper 2-stroke oil pre-mix
Premix Ratio:
50:1 (recommended, check manual for specific oil type)
Transmission Type:
Constant-mesh 6-speed
Clutch Type:
Wet, multi-plate
Gear Ratios:
Specific ratios detailed within the manual (e.g., 1st: 2.615, 2nd: 1.857, 3rd: 1.400, 4th: 1.136, 5th: 0.958, 6th: 0.833)
Transmission Oil Type:
Yamalube 2R or equivalent high-quality 2-stroke oil (for pre-mix)
Oil Change Frequency:
Pre-mix oil is consumed during operation; gearbox oil typically every 10-15 hours of riding. Manual will specify.
Air Filter Cleaning:
Frequent cleaning or replacement recommended based on riding conditions (every few hours of dusty riding).
Spark Plug Replacement:
Intervals vary; typically every 15-25 hours depending on usage. Manual will provide specifics.
Top End Rebuild:
Recommended every 40-80 hours of hard riding, depending on components and care. Manual will detail.
Gearbox Oil:
Yamalube Gear Oil or equivalent SAE 80 API GL-4 transmission fluid.
Coolant:
Permanent type antifreeze (ethylene glycol based) mixed 50/50 with distilled water.
Brake Fluid:
DOT 3 or DOT 4 hydraulic brake fluid.
Two Stroke Care:
Proper pre-mix ratio and high-quality oil are crucial for engine longevity. Carbon buildup in the exhaust and power valve system is common.
Suspension Maintenance:
Regular fork seal inspection and fork oil changes are vital for optimal suspension performance.
Carburetor Tuning:
May require jetting adjustments based on altitude, temperature, and modifications. The manual is key for correct tuning.
Yamaha Motorcycles:
Yamaha Motor Company, established in 1955, has a rich history in motorsports, particularly in motocross and road racing.
Yz Series Development:
The YZ250 has been a dominant force in motocross since its inception, with continuous development in engine technology, suspension, and chassis design.
1992 Updates:
The 1992 model likely saw refinements over previous years, potentially including updated suspension valving, chassis geometry tweaks, and engine tuning improvements for enhanced performance.
Production Era:
The YZ250 platform has been in continuous production for decades, with the 1992 model representing a key iteration in its development.
