Segment:
Motocross / Off-Road Competition
Target User:
Enthusiast owners, amateur racers, professional mechanics
Competition:
Competes with other 125cc two-stroke motocross bikes from brands like KTM, Honda, Suzuki, and Kawasaki.
Vehicle Focus:
High-performance, lightweight, agile motocross machine.
Manual Purpose:
To provide comprehensive technical guidance for maintenance, repair, and optimal performance tuning.
Geographic Coverage:
Italy, France, Germany (Indicates regional applicability or language focus)
Estimated Page Count:
Detailed (Exact count not provided in product info, but implies comprehensive coverage)
Type:
Workshop Repair Manual
Primary Languages:
English (ENG), Italian (ITA), French (FR), German (GER)
Download Format:
Instant Download (Likely PDF)
Engine:
Complete engine assembly, disassembly, tuning, diagnostics, and component repair
Transmission:
Gearbox operation, disassembly, assembly, clutch system, lubrication
Chassis:
Frame, suspension (front and rear), steering, swingarm, wheel bearings
Brakes:
Front and rear brake systems (hydraulic disc), master cylinders, calipers, lines, bleeding procedures
Electrical System:
Ignition system, lighting, wiring diagrams, charging system, CDI unit
Fuel System:
Carburetor (e.g., Mikuni VM series), fuel tank, fuel lines, fuel filter
Cooling System:
Liquid-cooled engine: radiator, water pump, hoses, coolant specifications
Exhaust System:
Exhaust pipe, silencer, mounting, maintenance
Bodywork And Controls:
Handlebars, levers, footpegs, seat, body panels, decals
Routine Maintenance:
Oil changes, filter replacements, chain adjustment, spark plug service, air filter cleaning
Disassembly And Assembly:
Step-by-step instructions for all major components and systems
Troubleshooting:
Diagnostic guides for common problems, symptom-based troubleshooting charts
Rebuilds:
Complete engine rebuild procedures, including top-end and bottom-end overhauls
Adjustments:
Carburetor jetting, idle speed, clutch engagement, throttle cable
Lubrication Points:
Specific lubrication requirements and schedules for various components
Depth:
Comprehensive (Covers from basic maintenance to full engine rebuilds and advanced diagnostics)
Detail Level:
Detailed step-by-step instructions with torque specifications, clearances, and tolerances
Diagrams And Illustrations:
Includes exploded views, wiring diagrams, and detailed illustrations for component identification and assembly
Engine Type:
Liquid-cooled, 2-stroke, reed valve, single-cylinder
Displacement:
124 cc (Cubic Centimeters)
Bore X Stroke:
54.0 mm x 54.5 mm
Compression Ratio:
8.8:1 (Typical for this model year, confirmation in manual)
Carburetion:
Mikuni VM28SS (or similar specification)
Ignition:
Digital CDI (Capacitor Discharge Ignition)
Horsepower:
Approx. 35-38 HP (Varies by tuning and specific market, manual will provide OEM specs)
Torque:
Approx. 24-26 Nm (Varies by tuning and specific market, manual will provide OEM specs)
Fuel Type:
Unleaded gasoline with appropriate octane rating (91+ RON recommended, manual will specify)
Oil Mixing:
Pre-mix 2-stroke engine oil and gasoline (Ratio specified in manual, typically 50:1 or 40:1)
Fuel Tank Capacity:
Approx. 8.0 Liters (1.9 Gallons)
Oil Change Engine:
As per manual recommendations, typically every 10-15 hours of riding or annually.
Air Filter Cleaning:
Frequent cleaning recommended, especially after muddy conditions (every 2-5 hours).
Chain Lubrication Adjustment:
Regular lubrication (every 5-10 hours) and adjustment for proper tension.
Spark Plug Service:
Inspect and clean/replace as needed, typically every 20-30 hours.
Top End Rebuild:
Recommended every 50-75 hours of aggressive riding (manual will provide specific guidance).
Engine Oil Type:
Premium 2-stroke engine oil formulated for high-performance off-road applications (specific viscosity and API/JASO ratings in manual).
Transmission Oil Type:
Yamaha's recommended gear oil or equivalent SAE 10W-30 or 10W-40 API GL-4 gear lubricant (manual will confirm).
Coolant Type:
Permanent type antifreeze/coolant with a 50/50 mix of water (manual will specify capacity and type).
Common Wear Items:
Clutch plates, piston rings, spark plugs, and chain/sprockets are common wear items requiring regular inspection and replacement.
Carburetor Tuning:
Proper carburetor jetting is crucial for optimal performance and preventing engine damage; this manual provides detailed guidance.
Overheating:
Can occur with improper coolant levels or radiator blockages; manual covers cooling system checks.
Manufacturer:
Yamaha Motor Company, renowned for its performance motorcycles and motorsports.
Yz Lineage:
The YZ125 is part of Yamaha's long-standing and successful YZ motocross line, known for its innovation and racing pedigree.
Production Years:
The YZ125 has been in continuous production since its introduction in the 1970s, with the 2005 model representing an evolution of this successful platform.
