Vehicle Segment:
Lightweight, urban-focused moped, popular for its simplicity and economy.
Competitors:
Competed with other entry-level mopeds from brands like Honda (e.g., Spree, Aero), Suzuki (e.g., FA50), and Tomos.
Design Philosophy:
Yamaha's QT50 was designed as an accessible, easy-to-operate, and fuel-efficient personal transport solution for city commuting.
Target Audience:
Young riders, commuters seeking economical transportation, and those new to motorcycling.
Engine System:
Detailed coverage of the 2-stroke engine, including disassembly, inspection, and reassembly of all components such as the cylinder, piston, crankshaft, and bearings.
Carburetion And Fuel Delivery:
Comprehensive information on the carburetor (likely a Mikuni VM series), fuel petcock, fuel lines, and air filter system, including adjustment and cleaning procedures.
Ignition System:
Detailed guidance on the CDI (Capacitor Discharge Ignition) system, including stator, ignition coil, spark plug, and timing adjustments.
Transmission And Drive System:
Coverage of the automatic centrifugal clutch, V-belt drive system, and final drive mechanism (gearbox).
Electrical System And Lighting:
Includes wiring diagrams, lighting system components (headlight, taillight, turn signals), battery charging system, and switchgear operations.
Braking System:
Detailed instructions for front and rear brake systems (likely drum brakes for this era), including adjustment, inspection, and replacement of brake shoes and cables.
Suspension And Steering:
Information on front fork assembly, rear shock absorber(s), and steering head bearing maintenance and adjustment.
Wheels And Tires:
Specifications for wheel sizes, tire types, inflation pressures, and wheel bearing maintenance.
Chassis And Frame:
Details on frame inspection, fastener torque specifications, and general chassis maintenance.
Bodywork And Cosmetics:
Guidance on removal and installation of body panels, seat, and other cosmetic components.
Routine Maintenance:
Step-by-step guides for oil changes (for gearbox), air filter cleaning/replacement, spark plug checks, and brake adjustments.
Engine Overhaul:
Complete instructions for engine disassembly, cleaning, inspection for wear, and reassembly, including critical component measurements.
Carburetor Tuning:
Procedures for cleaning, rebuilding, and adjusting the carburetor for optimal performance and fuel economy.
Electrical Troubleshooting:
Systematic methods for diagnosing electrical faults using wiring diagrams, multimeter readings, and component testing.
Brake System Service:
Detailed procedures for adjusting, inspecting, and replacing brake components.
Suspension And Steering Adjustment:
Guidance on servicing and adjusting suspension linkages and steering components.
Tire And Wheel Service:
Instructions for tire pressure checks, tire replacement, and wheel bearing maintenance.
Diagnostic Charts:
Common problems and their probable causes and solutions, presented in easy-to-follow diagnostic flowcharts.
Depth:
Comprehensive rebuilds and advanced diagnostics, suitable for professional technicians and experienced DIY mechanics.
Engine Type:
2-stroke, air-cooled single cylinder
Bore X Stroke:
Approx. 39.5 mm x 40.8 mm (typical for 49cc 2-strokes, specific value requires manual)
Compression Ratio:
Typically around 7.0-7.5:1 (specific value requires manual)
Power Output:
Approx. 3-4 HP (specific value requires manual)
Torque Output:
Approx. 2.5-3.5 Nm (specific value requires manual)
Top Speed:
Governed by local regulations, typically around 30-35 mph.
Carburetor Model:
Likely Mikuni VM12 or similar (specific model number found in manual)
Fuel Type:
Unleaded gasoline with 2-stroke oil mixture (e.g., 50:1 or as specified by Yamaha)
Fuel Tank Capacity:
Approx. 3.5 Liters (specific value requires manual)
Fuel Delivery:
Gravity feed from fuel tank via petcock to carburetor.
Overall Length:
Approx. 1750 mm (specific value requires manual)
Overall Width:
Approx. 650 mm (specific value requires manual)
Overall Height:
Approx. 1050 mm (specific value requires manual)
Wheelbase:
Approx. 1200 mm (specific value requires manual)
Dry Weight:
Approx. 70-75 kg (specific value requires manual)
Gross Vehicle Weight Rating:
Not typically specified in detail for mopeds, but rider + cargo limit implied.
Payload Capacity:
Typically 1 rider + modest cargo.
Oil Change Gearbox:
Every 3,000 km or annually (specific interval in manual).
Air Filter Cleaning:
Every 1,000 km or as needed based on operating conditions (specific interval in manual).
Spark Plug Inspection:
Every 1,000 km (specific interval in manual).
Brake Adjustment:
Inspect and adjust every 2,000 km or as needed (specific interval in manual).
Gearbox Oil Type:
Yamaha Gear Oil (or equivalent SAE 80W API GL-III hypoid gear oil), capacity approx. 0.7 Liters (verify in manual).
2 Stroke Oil Type:
High-quality 2-stroke engine oil, pre-mix ratio typically 50:1 (confirm in manual).
Brake Fluid:
N/A (Drum brakes typically do not use hydraulic fluid).
Carburetor Clogging:
Common with older 2-strokes due to fuel varnish if left sitting; requires cleaning/rebuilding.
Ignition Coil Failure:
Can be a point of failure, leading to no spark.
V-Belt Wear:
CVT belts wear over time and can slip or break, affecting acceleration and top speed.
Crankshaft Seals:
Leaking crank seals can cause vacuum leaks and poor engine running.
Exhaust Decarbonization:
2-stroke exhaust ports and mufflers can carbon up, reducing performance and causing smoky exhaust.
Yamaha Motors:
Yamaha Motor Corporation is a globally recognized manufacturer of motorcycles, scooters, marine products, and musical instruments, known for its engineering and performance.
Qt50 Lineage:
The QT50 was part of Yamaha's lineup of lightweight, entry-level scooters and mopeds designed for accessible personal transportation during the 1980s.
Production Period:
The QT50 model was produced in the early to mid-1980s.
Manufacturing Location:
Likely manufactured in Japan or potentially other Yamaha overseas facilities.