Category:
Lightweight Scooter / Moped
Target Audience:
Enthusiasts, owners, mechanics, and restoration projects for Yamaha QT50 scooters.
Competitors:
Honda Spree, Honda Elite, Tomos models, various other 50cc class scooters of the era.
Vehicle Type:
Compact, air-cooled, 2-stroke, automatic transmission scooter.
Manual Utility:
Essential resource for maintaining the longevity and performance of the vintage QT50.
Applicable Model Years:
1979, 1980, 1981, 1982, 1983, 1984, 1985, 1986, 1987, 1988, 1989, 1990, 1991, 1992
Engine Variants Covered:
All QT50 variants within the specified years
Geographic Coverage:
Global (specifications may vary by region)
Estimated Page Count:
Varies based on specific edition, typically 200-300 pages for comprehensive coverage
Type:
Service Manual / Repair Manual
Engine:
Detailed breakdown of the 49cc 2-stroke engine, including top-end, bottom-end, carburetor, ignition, and cooling systems.
Transmission:
Coverage of the automatic CVT (Continuously Variable Transmission) system, including belt inspection, clutch operation, and variator servicing.
Fuel System:
In-depth information on the fuel tank, fuel lines, fuel filter, and the Mikuni carburetor (specific model dependent).
Electrical System:
Wiring diagrams, lighting system (headlight, taillight, turn signals), battery maintenance, ignition system troubleshooting, and starter system.
Chassis And Suspension:
Front fork inspection and service, rear shock absorber replacement, steering system maintenance, and frame component checks.
Brakes:
Front and rear brake system service, including adjustment, shoe/pad replacement, and drum/disc inspection.
Bodywork And Trim:
Information on fairings, body panels, seat, handlebars, and cosmetic component removal and installation.
Wheels And Tires:
Wheel bearing maintenance, tire pressure specifications, and tire replacement procedures.
Routine Maintenance:
Oil changes (gear oil), spark plug replacement, air filter cleaning/replacement, brake adjustments, and general inspection procedures.
Troubleshooting:
Diagnostic flowcharts and common problem identification for starting issues, running problems, and electrical faults.
Repair And Overhaul:
Step-by-step instructions for engine disassembly and reassembly, carburetor overhaul, transmission servicing, and component replacement.
Technical Data And Specifications:
Torque specifications for all fasteners, engine timing, carburetor jetting data, and electrical component resistance values.
Depth:
Comprehensive, covering from basic user maintenance to complete engine rebuilds and diagnostic procedures.
Diagnostic Capabilities:
Detailed troubleshooting guides and symptom-based diagnostics for mechanical and electrical issues.
Rebuild Instructions:
Complete overhaul procedures for major components like the engine and transmission.
Searchability:
Likely text-searchable, allowing for quick navigation to specific topics.
Quality:
High-resolution scans ensuring clarity of text and diagrams.
Binding:
Not Applicable (Digital PDF Download)
Paper Type:
Not Applicable (Digital PDF Download)
Engine Type:
2-stroke, air-cooled
Displacement:
49cc (approximately)
Bore X Stroke:
Typically 39.0 mm x 41.4 mm (check specific manual for exact figures)
Compression Ratio:
Check manual, usually around 6.0:1 to 7.0:1
Ignition System:
CDI (Capacitor Discharge Ignition)
Spark Plug Type:
NGK B-PR6HS (or equivalent, consult manual for exact spec)
Carburetor Type:
Mikuni VM series (e.g., VM10-1, VM15-1, specific model dependent)
Horsepower Output:
Approx. 4.0 - 5.0 HP (check specific manual for exact figures)
Torque Output:
Not typically a primary spec for this class, but covered in manual.
Fuel Type:
Unleaded gasoline
Fuel Mixture Ratio:
50:1 (Gasoline: 2-stroke oil) - CRITICAL to follow manual's recommendation
Fuel Tank Capacity:
Approximately 3.0 - 4.0 Liters (check specific manual)
Carburetor Size:
Typically 14mm to 16mm bore (e.g., VM14SH)
Type:
Automatic Continuously Variable Transmission (CVT)
Clutch Type:
Centrifugal clutch
Drive Belt Maintenance:
Inspection and replacement intervals for the drive belt.
Gear Reduction:
Final drive via chain or gear reduction (manual will specify)
Gear Oil Type:
Yamalube Gear Oil or equivalent SAE 80W API GL-4 (check manual for precise specification)
Gear Oil Capacity:
Approximately 0.07 - 0.10 Liters (check manual)
Overall Length:
Refer to specific manual, typically around 1500-1600 mm
Overall Width:
Refer to specific manual, typically around 600-700 mm
Overall Height:
Refer to specific manual, typically around 1000-1100 mm
Dry Weight:
Approximately 60-70 kg (check specific manual)
Gross Vehicle Weight Rating:
Consult manual for specific load capacity
Front Tire Size:
Typically 2.50-10 or 3.00-10 (consult manual)
Rear Tire Size:
Typically 2.50-10 or 3.00-10 (consult manual)
Front Wheel Type:
Cast or spoke (verify in manual)
Rear Wheel Type:
Cast or spoke (verify in manual)
Wheelbase:
Refer to specific manual, typically around 1150-1200 mm
Crash Test Ratings:
Not applicable for this vehicle class/era in a modern sense.
Lighting:
Headlight, taillight, brake light, turn signals (coverage in manual).
Frame Construction:
Steel tube frame (details in manual).
Braking System:
Drum brakes front and rear (manual details adjustment and maintenance).
Oil Change Interval:
Gear oil: Every 3,000 km or 1 year. 2-stroke oil: Continuous mixing with fuel, ensure adequate 2-stroke oil in reservoir.
Air Filter Cleaning:
Every 1,000 km or 6 months (clean and re-oil if applicable).
Spark Plug Replacement:
Every 3,000 km or 1 year, or as needed based on inspection.
Brake Adjustment:
As needed, typically checked at every 1,000 km service.
Two Stroke Oil:
API TA, API TB, or API TC rated 2-stroke motorcycle oil (Yamalube 2-M is recommended). Check manual for precise classification.
Gear Oil Specification:
SAE 80W API GL-4 Gear Oil (e.g., Yamalube Gear Oil).
Carburetor Fouling:
Common with older 2-strokes due to oil mixture and idling; regular cleaning is essential.
Cvt Belt Wear:
Drive belts have a service life and require periodic inspection and replacement to prevent sudden failure.
Ignition System Issues:
CDI units or stator coil failures can cause no-spark conditions.
Fuel Petcock Leaks:
Older rubber components can degrade, leading to fuel leaks.
Throttle Cable Sticking:
Due to age, dirt, or improper routing, the throttle can become sticky.
Manufacturer Focus:
Yamaha is renowned for its musical instruments and powersports vehicles, including motorcycles and scooters.
Qt50 Placement:
The QT50 was Yamaha's entry into the highly competitive 50cc scooter market, offering a simple, reliable, and user-friendly mode of transportation.
Production Period:
1979-1992
Manufacturing Location:
Likely Japan, but specific plant details may require deeper research or manual consultation.
Awards Achieved:
While specific awards for the QT50 are not widely documented, it was a popular and well-regarded model in its segment for its reliability and affordability.
Consumer Satisfaction:
Generally positive for its intended use as economical urban transport.
Emissions Compliance:
Designed to meet emissions standards of its era, details on specific certifications would be in the manual.
