Positioning:
The Yamaha QT50 was a popular, lightweight, 2-stroke scooter designed for urban commuting and recreational use. Known for its simplicity, fuel efficiency, and ease of operation, it appealed to a wide demographic, including younger riders and those seeking an economical mode of transportation.
Competitors:
Competed with other small-displacement scooters and mopeds from brands like Honda (e.g., Spree, Aero), Tomos, Puch, and various European and Asian manufacturers of the era.
Features:
Automatic transmission (CVT), lightweight frame, reliable 2-stroke engine, simple controls, iconic 70s/80s styling, relatively low maintenance requirements.
Years Covered:
1979, 1980, 1981, 1982, 1983, 1984, 1985, 1986, 1987, 1988, 1989, 1990, 1991, 1992
Geographic Coverage:
Global (typically covers specifications relevant to North American and European markets unless otherwise specified)
Estimated Page Count:
200-300 pages (estimated based on typical service manual depth for this era of scooter)
Type:
Repair Service Manual
Engine Mechanical:
Engine disassembly, assembly, inspection, repair procedures, cylinder head, piston, crankshaft, connecting rod, lubrication system, cooling system (air-cooled).
Fuel System:
Carburetor identification, disassembly, cleaning, adjustment, fuel tank, fuel lines, fuel filter replacement.
Ignition System:
CDI unit, ignition coil, spark plug specifications, timing procedures, troubleshooting ignition faults.
Electrical System:
Wiring diagrams, lighting system (headlight, taillight, turn signals), charging system (stator, rectifier/regulator), battery maintenance, horn, switches.
Transmission Drive:
Automatic transmission (CVT - Continuously Variable Transmission) components (variator, clutch, drive belt inspection and replacement), final drive gears, lubrication.
Chassis Frame:
Frame inspection, steering system disassembly and repair, front fork (suspension) overhaul, rear shock absorber replacement.
Braking System:
Front and rear drum brake systems, brake shoe inspection and replacement, brake lever and cable adjustment.
Wheels Tires:
Wheel bearing inspection and replacement, tire pressure specifications, tire replacement procedures.
Bodywork Trim:
Body panel removal and installation, seat, fenders, handlebars, controls.
Maintenance:
Scheduled maintenance intervals, lubrication points, filter changes, fluid checks and top-offs.
Troubleshooting:
Diagnostic flowcharts for common problems, electrical system troubleshooting, engine performance issues, starting difficulties.
Repair:
Step-by-step repair instructions for all major components and systems.
Overhaul:
Detailed procedures for engine rebuilds and component overhauls.
Adjustment:
Carburetor, brake, clutch, and throttle cable adjustments.
Depth:
Comprehensive, covering everything from basic maintenance and adjustments to complete engine and transmission overhauls, including detailed diagnostic procedures.
Engine Type:
2-stroke, single-cylinder, reed valve induction
Displacement:
49.2 cc (3.00 cu in)
Bore X Stroke:
37.0 mm x 37.0 mm (1.46 in x 1.46 in)
Compression Ratio:
7.0:1 (approximate, subject to variation)
Cooling System:
Forced air-cooled
Carburetor Model:
Mikuni VM15SC (typical, may vary slightly by year/market)
Horsepower:
Approximately 4.0 - 4.5 HP at 6000 RPM (manufacturer specified, actual may vary)
Torque:
Not typically advertised for this class, but robust for its displacement.
Fuel Type:
Unleaded gasoline, minimum 87 octane recommended
Fuel Mixture:
2-stroke oil mixed with gasoline at a 50:1 ratio (or as specified in manual)
Fuel Tank Capacity:
Approx. 3.5 Liters (0.92 US gal)
Overall Length:
Approx. 1700 mm (66.9 in)
Overall Width:
Approx. 645 mm (25.4 in)
Overall Height:
Approx. 1035 mm (40.7 in)
Wheelbase:
Approx. 1170 mm (46.1 in)
Ground Clearance:
Approx. 115 mm (4.5 in)
Dry Weight:
Approx. 70 kg (154 lbs)
Curb Weight:
Approx. 75 kg (165 lbs) (with fluids)
Max Load Capacity:
Typically around 150-180 kg (330-400 lbs), including rider and cargo.
Crash Test Ratings:
Not applicable for scooters of this era and classification.
Braking System:
Front and rear drum brakes, operated by handlebar levers.
Lighting:
Headlight, taillight, brake light, turn signals, instrument panel illumination.
Frame Construction:
Steel tube frame providing rigidity.
Suspension:
Telescopic front forks, swingarm rear suspension with dual shock absorbers.
Oil Change Engine:
Not applicable for 2-stroke (oil mixed with fuel). Check crankcase for slight oil leak/lubrication if applicable, but primarily focuses on transmission oil.
Transmission Oil Change:
Every 5,000 - 10,000 km (3,000 - 6,000 miles) or annually, refer to manual for specific intervals and oil type.
Air Filter Cleaning:
Inspect every 1,000 km (600 miles), clean or replace as needed. More frequently in dusty conditions.
Spark Plug Replacement:
Inspect every 2,000 km (1,200 miles), replace as needed. Recommended replacement interval typically 10,000 - 15,000 km.
Drive Belt Inspection:
Inspect every 5,000 km (3,000 miles), replace based on wear (cracking, fraying) or mileage. Typical replacement at 20,000 - 30,000 km.
Brake Pad Shoe Inspection:
Inspect every 2,000 km (1,200 miles) or as part of regular checks.
Transmission Oil Type:
Yamalube Gear Oil 10W-30 or equivalent API GL-4 or GL-5.
2 Stroke Oil Type:
Yamalube 2-stroke oil or equivalent API TC, JASO FB certified.
Fuel Octane Rating:
Minimum 87 Octane Unleaded Gasoline.
Carburetor Clogging:
Common with older 2-strokes due to fuel varnish and sediment. Requires regular cleaning.
Drive Belt Wear:
Belts can stretch or crack over time, leading to poor acceleration or slipping.
Electrical Connections:
Corrosion on connectors can lead to intermittent lighting or starting issues.
Intake Manifold Cracking:
Rubber intake boots can become brittle and crack, causing air leaks and poor running.
Exhaust Port Carbon Buildup:
Typical for 2-strokes, can lead to reduced performance if not cleaned periodically.
Heritage:
Yamaha Motor Corporation, founded in 1955, has a rich history in motorcycle and powersports manufacturing, known for innovation and performance across a wide range of vehicles.
Evolution:
The QT50 was part of Yamaha's lineup of small-displacement, user-friendly scooters and mopeds. While it remained largely consistent throughout its production run, minor updates for emissions or aesthetics may have occurred depending on the market. It paved the way for later Yamaha scooter models.
Production Years:
1979-1992
Manufacturing Location:
Primarily Japan (typical for Yamaha).
