Market Position:
The Yamaha QT50 QT 50 was a popular lightweight scooter in the early 1980s, catering to urban commuters and recreational riders seeking an economical and easy-to-operate two-wheeled vehicle. This manual targets owners and technicians responsible for maintaining and repairing this specific model.
Competitive Analysis:
Competed with other 50cc scooters from brands like Honda (e.g., Aero 50), Suzuki (e.g., Street Magic), and Tomos. The QT50 was known for its reliable two-stroke engine and distinctive styling.
Key Features:
Focus on ease of use, fuel efficiency, and Yamaha's reputation for quality and reliability in the personal mobility sector. The QT50 often featured automatic transmission and simple controls.
Systems Covered:
Engine disassembly, assembly, tuning, lubrication, cooling system, fuel system, ignition system, exhaust system, clutch, transmission, frame, suspension (front and rear), steering, brakes (front and rear), electrical system (lighting, ignition, battery, wiring diagrams), chassis components, bodywork, troubleshooting, diagnostic procedures, specifications.
Electrical System Details:
Includes detailed wiring diagrams, component testing, troubleshooting for lighting, ignition, charging system, and starter (if electric start equipped).
Suspension And Steering Details:
Covers front telescopic fork and rear swingarm suspension maintenance, fork oil replacement, bushing inspection, and steering bearing adjustments.
Procedures Included:
Detailed step-by-step repair instructions, disassembly and reassembly procedures, component testing, adjustment procedures (e.g., carburetor, ignition timing, brakes), troubleshooting common faults, replacement of wear items, torque specifications, electrical system diagnostics, preventive maintenance schedules.
Engine Rebuild Procedures:
Comprehensive instructions for complete engine teardown, inspection of cylinder, piston, crankshaft, bearings, and reassembly with torque specifications.
Wheel And Tire Service:
Includes procedures for wheel removal, tire replacement, balancing, and checking tire pressures. Specific tire sizes and inflation pressures will be detailed.
Technical Depth:
Designed for professional technicians, implying deep technical detail, including internal component specifications, critical tolerances, diagnostic flowcharts, and advanced repair techniques. Adequate data for experienced DIY mechanics as well.
Diagnostic Charts:
Likely includes diagnostic flowcharts for common problems, enabling systematic troubleshooting.
Engine Type:
Two-stroke, air-cooled
Displacement:
49 cc (2.99 cu in)
Bore X Stroke:
39.0 mm x 41.8 mm (1.54 in x 1.65 in) - Approximate, requires manual verification
Compression Ratio:
7.3:1 - Approximate, requires manual verification
Carburetor Type:
Mikuni VM14SC (typical for this model) - Requires manual verification for exact part number and settings
Ignition System:
CDI (Capacitor Discharge Ignition)
Lubrication:
Autolube (pre-mix oil injection)
Air Filter Type:
Foam or paper element (specific type and maintenance schedule detailed in manual).
Spark Plug Type:
NGK B8HS or equivalent (specific recommendation and gap in manual).
Horsepower:
Approx. 4.3 HP @ 6500 RPM - Requires manual verification
Torque:
Not typically published for this class of vehicle, but available in the manual.
Fuel Type:
Unleaded gasoline
Fuel Tank Capacity:
Approx. 3.0 Liters (0.79 US gal) - Requires manual verification
Length:
Approx. 1750 mm (68.9 in) - Requires manual verification
Width:
Approx. 650 mm (25.6 in) - Requires manual verification
Height:
Approx. 1000 mm (39.4 in) - Requires manual verification
Wheelbase:
Approx. 1220 mm (48.0 in) - Requires manual verification
Ground Clearance:
Approx. 120 mm (4.7 in) - Requires manual verification
Dry Weight:
Approx. 70 kg (154 lbs) - Requires manual verification
Payload Capacity:
Not typically specified for this class of vehicle, but available in the manual.
Safety Ratings:
N/A (Vehicle class does not typically undergo formal crash testing as per automotive standards).
Active Features:
Front and rear drum brakes, front suspension, rear suspension.
Passive Features:
Headlight, taillight, turn signals, brake light, horn.
Initial Service:
Typically around 500-1000 km (300-600 miles) for first service, including oil change, filter check, and general inspection. Manual will provide exact intervals.
Regular Service:
Detailed intervals for oil changes, spark plug replacement, air filter cleaning/replacement, carburetor cleaning, brake adjustment, chain inspection/lubrication (if applicable, though this is belt drive), and general component checks will be specified in the manual.
Engine Oil Type:
2-stroke motorcycle oil (specific API classification and viscosity grade, e.g., API TC, SAE 10W-30, will be detailed in manual).
Transmission Oil Type:
N/A (CVT with oil bath clutch, lubrication is integrated or via specific sealed units - manual to confirm).
Gear Oil:
Specific viscosity and capacity for final drive gears will be detailed in the manual.
Coolant Type:
N/A (Air-cooled engine)
Brake Fluid Type:
DOT 3 or DOT 4 (for drum brake systems, fluid type and inspection frequency will be in the manual).
Common Issues:
Typical for older 2-stroke scooters: carburetor gumming, air leaks in intake manifold leading to lean conditions, worn drive belts, aging electrical components, piston ring wear. Manual provides troubleshooting for these.
Preventive Maintenance:
Regular cleaning of the carburetor, checking for air leaks, proper fuel mixture, and timely replacement of spark plugs and air filters are crucial for longevity.
Brand Heritage:
Yamaha Motor Corporation, a subsidiary of Yamaha Corporation, has a long history in motorcycle and scooter manufacturing, dating back to the early 1950s. Known for innovation and performance across various motorized products.
Model Evolution:
The QT50 was part of Yamaha's expansion into the lightweight scooter market during the early 1980s, a period of growing interest in fuel-efficient personal transportation. It was succeeded by models with more modern designs and features.
Key Innovations For Era:
The QT50, typical of its era, featured an automatic transmission and autolube system, simplifying operation and maintenance for the user compared to earlier manual transmission motorcycles or those requiring manual oil mixing.
Production Years:
Mid-1980s (specific production run for 1982 model year, likely continued for several years thereafter).
