Vehicle Segment:
Lightweight scooter, commuter segment.
Key Competitors:
Competes with other 125cc scooters from brands like Honda (e.g., Lead 125, Dio 125), Suzuki (e.g., Address 125), Kymco, and SYM during its production years.
Target Audience:
Designed for urban commuting, offering ease of use, fuel efficiency, and practicality.
Manual Value Proposition:
Provides comprehensive, factory-level information essential for maintenance, repair, and diagnostics, empowering owners and technicians to keep the YJ125S in optimal condition.
Model Years Covered:
2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010
Estimated Page Count:
Hundreds of pages (specific count not provided in source but typical for a comprehensive workshop manual)
Manual Type:
Workshop Service Repair Manual
Language:
English (assumed based on product description phrasing for a global market)
Engine And Powertrain:
Detailed coverage of the 125cc engine, including disassembly, assembly, tuning, diagnostics, and overhaul of all internal and external components.
Fuel And Emission Systems:
Carburetor system (adjustments, cleaning, rebuilding), fuel lines, fuel tank, emission control systems (if applicable for the target market).
Cooling System:
Air cooling system diagnosis and maintenance.
Ignition System:
CDI ignition system, spark plug diagnosis, ignition timing.
Electrical System:
Wiring diagrams, lighting system (headlight, taillight, indicators), battery, charging system (alternator/stator, regulator/rectifier), starter system.
Chassis And Suspension:
Front fork (disassembly, seal replacement, oil levels), rear shock absorber(s), swingarm, bearings (steering head, wheel).
Brake System:
Front and rear drum brake systems (adjustment, pad replacement, drum inspection), brake lever, cables.
Wheel And Tires:
Wheel bearing inspection and replacement, tire pressure, tire inspection and replacement guidance.
Bodywork And Fittings:
Body panels, seat, storage compartments, handlebars, controls (throttle, brake levers), instrument cluster.
Routine Maintenance:
Oil changes, filter replacements, chain adjustment, tire pressure checks, spark plug replacement, general inspection.
Troubleshooting:
Step-by-step diagnostic procedures for common and uncommon issues, fault finding charts.
Engine Repair:
Complete engine disassembly, inspection, repair, and reassembly for all internal components (piston, rings, cylinder, crankshaft, valve train).
Carburetor Rebuild:
Detailed instructions for cleaning, inspecting, and replacing carburetor components and jets.
Electrical Diagnostics:
Testing of electrical components, troubleshooting wiring faults using diagrams, stator testing, regulator/rectifier testing.
Suspension Overhaul:
Front fork seal replacement, fork oil change, rear shock absorber inspection.
Brake Maintenance:
Brake shoe replacement, drum cleaning, cable lubrication and adjustment.
Wheel And Tire Service:
Wheel bearing replacement, tire mounting and balancing guidance.
Depth Of Coverage:
Comprehensive (full factory service manual level), covering everything from routine maintenance to complete engine and chassis overhauls, including detailed specifications and diagnostic procedures.
Engine Type:
4-stroke, SOHC, forced air-cooled
Bore X Stroke:
52.0 mm x 57.9 mm (typical for this engine family, confirm with manual)
Compression Ratio:
10.0:1 (typical, confirm with manual)
Horsepower:
Approximately 8.1 hp @ 7,500 rpm (estimated for the period, actual figures may vary by market and tune)
Torque:
Approximately 8.4 Nm @ 6,500 rpm (estimated, actual figures may vary)
Fuel Delivery System:
Carburetor (likely a VM20 or similar Mikuni/Keihin unit, specific model in manual)
Fuel Type:
Unleaded Gasoline
Oil Type:
Yamaha recommends SAE 10W-30 or 20W-40 API SG or higher (confirm specific grade and capacity in manual).
Ignition System:
Digital CDI
Starter:
Electric and Kick Starter
Overall Length:
Approx. 1830 mm (68.1 in) (typical for class, confirm in manual)
Overall Width:
Approx. 670 mm (26.4 in) (typical for class, confirm in manual)
Overall Height:
Approx. 1130 mm (44.5 in) (typical for class, confirm in manual)
Dry Weight:
Approx. 100 kg (220 lbs) (typical for class, confirm in manual)
Gross Vehicle Weight Rating:
Not explicitly specified, but includes rider and cargo capacity.
Fuel Tank Capacity:
Approx. 7.2 Liters (1.9 US gal) (typical for class, confirm in manual)
Wheelbase:
Approx. 1280 mm (50.4 in) (typical for class, confirm in manual)
Initial Service:
Typically at 1000 km or 1 month, covering oil change, filter check, and general inspection (refer to manual for exact schedule).
Regular Oil Change:
Every 3000 km or 6 months (confirm specific interval and oil type in manual).
Air Filter Cleaning Replacement:
Every 6000 km or 12 months (cleaning/replacement frequency depends on operating conditions, refer to manual).
Spark Plug Check Replacement:
Check every 6000 km, replace as needed (refer to manual for specific plug type and gap).
Engine Oil Capacity:
Approx. 0.9 Liters (0.95 US qt) when filter is not removed, 1.0 Liters (1.05 US qt) when filter is removed (confirm in manual).
Gear Oil Type:
Yamaha Gear Oil or equivalent SAE 80 API GL-4 (confirm type and capacity in manual).
Common Wear Items:
Brake shoes, drive belt, tires, spark plug, battery, suspension bushings due to normal wear and tear from commuting.
Carburetor Maintenance:
Carburetors can become gummed up if the vehicle sits for extended periods, requiring cleaning and adjustment. Carburetor jetting might need recalibration if used at significantly different altitudes.
Electrical Connections:
Corrosion on electrical connectors can sometimes lead to intermittent issues, particularly in humid or coastal environments. Regular inspection and cleaning are beneficial.
Yamaha History:
Yamaha Motor Company is renowned globally for its extensive history in motorcycle, scooter, and marine engine manufacturing, dating back to 1955. They are known for innovation, performance, and reliability across their product lines.
Yj125S Place In Lineup:
The YJ125S was part of Yamaha's scooter offerings, designed as a practical and economical urban transport solution, fitting into their broader strategy of providing a range of mobility options.
Production Years For Model:
2003-2010
Manufacturing Origin:
Likely manufactured in Southeast Asia (e.g., Indonesia, Thailand) or other global markets where Yamaha has manufacturing facilities for scooters. Specific factory details would be in production records, not typically in a service manual.
