Vehicle Class:
Lightweight Moped / Scooter
Target Market Segment:
Urban commuting, recreational riding.
Key Competitors Era:
Honda Spree, Tomos Revival, various other 50cc class mopeds of the early 1980s.
Engine Type:
Compact, air-cooled two-stroke engine for simplicity and lightness.
Transmission Type:
Automatic V-belt transmission (CVT) for ease of use.
Design Philosophy:
Focus on lightweight construction, maneuverability, and fuel efficiency.
Storage:
Integrated under-seat storage compartment.
Engine Mechanical:
Complete engine disassembly, assembly, inspection, and repair procedures.
Fuel System:
Carburetor inspection, cleaning, adjustment, and rebuilding; fuel tank and lines.
Ignition System:
Ignition timing, coil testing, spark plug specifications, and CDI unit troubleshooting.
Cooling System:
Air cooling system inspection and maintenance.
Transmission:
Automatic transmission (V-belt type) disassembly, inspection, adjustment, and repair.
Chassis Frame:
Frame inspection and alignment procedures.
Suspension Front:
Front fork disassembly, inspection, fluid replacement, and assembly.
Suspension Rear:
Rear shock absorber and swingarm inspection and maintenance.
Brakes Front:
Front drum brake inspection, adjustment, and lining replacement.
Brakes Rear:
Rear drum brake inspection, adjustment, and lining replacement.
Wheels Tires:
Wheel bearing inspection and lubrication, tire pressure recommendations.
Electrical System:
Wiring diagrams, lighting system, battery maintenance, horn, and indicators.
Bodywork Fittings:
Panel removal, seat, handlebars, and other body component maintenance.
Routine Maintenance:
Detailed steps for oil changes, filter replacement, lubrication, and general inspections.
Troubleshooting:
Systematic diagnostic flowcharts and common problem identification and resolution.
Engine Overhaul:
Step-by-step instructions for complete engine rebuilds, including torque specifications and clearances.
Transmission Repair:
Guidance on V-belt replacement, clutch inspection, and variator servicing.
Electrical Diagnostics:
Testing of electrical components, troubleshooting of starting and lighting issues.
Brake Adjustment:
Proper procedures for adjusting front and rear drum brakes for optimal performance.
Fork Service:
Front fork oil level checks, oil changes, and seal replacement.
Depth Level:
Comprehensive: Covers basic maintenance to complete engine and transmission rebuilds.
Diagnostic Focus:
Advanced troubleshooting, including electrical system diagnostics and component testing.
Engine Type:
2-stroke, air-cooled, single-cylinder
Bore X Stroke:
39.0 mm x 43.0 mm
Displacement:
49 cc (0.049 L)
Carburetor Model:
Mikuni VM11/17
Ignition System:
CDI (Capacitor Discharge Ignition)
Horsepower:
Approx. 4.0 PS @ 6000 rpm (manufacturer specification may vary)
Torque:
Not typically specified for this class, but estimated at around 0.45 kg-m.
Fuel Type:
Unleaded gasoline mixed with 2-stroke oil
Fuel Oil Ratio:
100:1 or 50:1 (refer to manual for exact specification)
Fuel Tank Capacity:
3.2 Liters (0.85 US gal)
Crash Test Ratings:
N/A (Moped class, no standardized crash testing for this era).
Braking System:
Front and rear drum brakes for reliable stopping power.
Lighting:
Headlight, taillight, brake light, turn signals for visibility.
Frame Construction:
Steel tube frame providing a sturdy platform.
Operator Ergonomics:
Designed for comfortable and controlled operation.
Oil Change Engine:
Refer to manual for two-stroke oil replenishment (automatic injection or premix).
Spark Plug Check:
Every 2,000-4,000 km (1,200-2,500 miles).
Air Filter Cleaning:
Every 2,000-4,000 km (1,200-2,500 miles).
Transmission Oil:
Regular checks and replenishment as needed (specific interval not always defined, but often checked with drive chain.
Engine Oil Type:
Yamalube 2 (or equivalent API TC, JASO FB rated 2-stroke oil).
Gear Oil:
Yamaha Gear Oil (or equivalent SAE 80 EP).
Fork Oil:
Yamaha Fork Oil (or equivalent SAE 10W).
Carburetor Clogging:
Common issue in older small-displacement engines due to fuel varnish if left sitting.
V-Belt Wear:
Wear and tear on the automatic transmission belt can lead to slipping or poor acceleration.
Ignition Coil Failure:
Can lead to no spark or intermittent spark, requiring replacement.
Electrical Connection Corrosion:
Typical for vehicles of this age, can cause intermittent electrical faults.
Manufacturer Founding:
Yamaha Motor Company founded in 1955, known for musical instruments and later motorcycles.
Qt50 Introduction:
The QT50 was part of Yamaha's entry into the popular moped market of the late 1970s and early 1980s.
Qt50 Design Focus:
Emphasized simplicity, low operating cost, and ease of use for a broad audience.
Production Period:
Early 1980s (1980-1983 approximately).
Manufacturing Location:
Primarily manufactured in Japan.
