Positioning:
The Yamaha QT50 was a popular, lightweight, and user-friendly scooter in its era, often marketed towards younger riders or for urban commuting due to its ease of operation and fuel efficiency.
Competitors:
Competed with other small-displacement scooters from manufacturers like Honda (e.g., Spree, Aero) and Suzuki (e.g., Streetmag). Its key differentiators were Yamaha's reputation for reliability and often distinctive styling.
Features:
Automatic transmission, lightweight design, electric start (often), and a compact 2-stroke engine providing peppy acceleration for its class.
Years Covered:
1979, 1980, 1981, 1982, 1983, 1984, 1985, 1986, 1987, 1988, 1989, 1990, 1991, 1992
Geographical Coverage:
Likely global, with specific regional variations noted if applicable to repair procedures.
Estimated Page Count:
Varies by specific edition, typically 200-400 pages for comprehensive manuals of this era.
Type:
Service Repair Manual
Engine:
Complete engine disassembly, assembly, tuning, troubleshooting, and overhaul procedures for the 2-stroke engine.
Fuel System:
Carburetor (Mikuni VM series likely) adjustment, cleaning, and overhaul; fuel tank, petcock, and fuel lines.
Ignition System:
CDI ignition system, spark plug diagnosis, coil testing, stator inspection.
Transmission:
Automatic transmission (CVT - Continuously Variable Transmission) inspection, belt replacement, clutch adjustment, and gearbox lubrication.
Brakes:
Front and rear drum brake systems, brake lever and cable adjustment, brake shoe replacement, and drum inspection.
Suspension:
Front telescopic forks (servicing, oil change, seal replacement) and rear shock absorber unit (inspection, replacement).
Electrical System:
Wiring diagrams, lighting (headlight, taillight, turn signals), horn, battery maintenance, fuse inspection, and basic electrical troubleshooting.
Cooling System:
Air-cooled engine design - focus on cylinder head and barrel fins for heat dissipation.
Chassis And Body:
Frame inspection, body panel removal and installation, seat, handlebars, and fairing components.
Maintenance:
Scheduled maintenance tasks, lubrication points, filter replacement, spark plug checks, and general upkeep.
Troubleshooting:
Diagnostic charts and procedures for common running issues, starting problems, and performance degradation.
Repair:
Detailed step-by-step instructions for component repair and replacement across all systems.
Rebuilds:
Engine and carburetor rebuild procedures with specifications and tolerances.
Adjustments:
Carburetor idle speed and mixture, brake lever free play, throttle cable slack.
Depth:
Comprehensive, covering basic maintenance to major overhaul and component-level repair.
Diagnostic Capability:
Includes diagnostic procedures and specifications for identifying and rectifying faults.
Format:
PDF (Portable Document Format)
Searchability:
Likely text-searchable PDF, allowing for quick navigation and keyword finding.
Quality:
Digital, quality is dependent on the source scan/creation but generally good for clarity of text and diagrams.
Type:
N/A (Digital format)
Type:
N/A (Digital format)
Engine Type:
2-stroke, air-cooled, single-cylinder
Displacement:
Approximately 49cc (specific figures may vary slightly by market variant).
Bore X Stroke:
Typical for this class: ~39.0mm x 41.4mm (check specific manual for exact figures).
Compression Ratio:
Likely around 7.0:1 to 7.5:1 (check specific manual).
Lubrication:
Pre-mix or Autolube system (automatic oil injection).
Horsepower:
Typically in the range of 4-6 HP at specific RPM (check manual for exact rating).
Torque:
Torque figures would be modest, optimized for low-end acceleration.
Carburetor Model:
Likely Mikuni VM Series (e.g., VM16SC or similar).
Fuel Type:
Unleaded gasoline
Fuel Octane Rating:
87 AKI (Anti-Knock Index) or higher.
Oil Type Autolube:
Yamaha recommended 2-stroke oil or equivalent API TC/JASO FD certified oil.
Type:
Automatic Continuously Variable Transmission (CVT)
Drive Type:
Belt drive from CVT to rear wheel.
Clutch Type:
Centrifugal automatic clutch
Gear Ratios:
Continuously variable via V-belt and pulleys. Specific pulley ratios and belt specifications available in manual.
Transmission Fluid:
Gear oil for the final drive. Specific viscosity and capacity detailed in the manual (likely SAE 80 or 90).
Overall Length:
Approx. 1660 mm (check manual for exact spec).
Overall Width:
Approx. 670 mm (check manual for exact spec).
Overall Height:
Approx. 1010 mm (check manual for exact spec).
Dry Weight:
Approx. 65-70 kg (check manual for exact spec).
Curb Weight:
Likely slightly higher than dry weight due to fluids.
Weight Distribution:
Designed for stability at low speeds, typically balanced.
Storage:
Under-seat storage compartment, rear luggage rack provisions.
Crash Test Ratings:
N/A (Scooters of this era were not typically subjected to standardized crash testing like modern automobiles).
Braking System:
Front and rear drum brakes for controlled stopping.
Lighting:
Headlight, taillight, brake light, and turn signals for visibility.
Frame Construction:
Steel frame designed for rigidity and rider support.
Handlebars:
Provide rider control and leverage.
Oil Change Final Drive:
Typically every 3,000-5,000 km or annually (refer to manual for precise interval).
Spark Plug Check:
Every 1,000-2,000 km or as needed for performance issues.
Air Filter Cleaning:
Every 1,000-2,000 km, depending on operating conditions.
Carburetor Cleaning:
As needed for performance issues, or proactively every 5,000-10,000 km.
Brake Adjustment:
Regularly check for proper lever free play.
Cvt Belt Inspection:
Inspect for wear and damage every 3,000-5,000 km, replace as necessary.
Transmission Oil Viscosity:
SAE 80 or SAE 90 Gear Oil (verify with manual).
2 Stroke Oil Type:
Yamaha Super 2-Stroke Oil, API TC, JASO FD (or equivalent).
Common Problems:
Carburetor gumming/clogging due to infrequent use or poor fuel quality, CVT belt wear, weak ignition spark due to CDI or coil failure, exhaust port restrictions from carbon buildup in the 2-stroke engine.
Preventative Maintenance:
Regular use to keep components clean and lubricated, using fresh fuel, and adhering to service intervals.
Heritage:
Yamaha Motor Corporation has a long history of producing high-quality motorcycles and scooters, known for innovation and performance.
Evolution:
The QT50, introduced in the late 1970s, represented Yamaha's offering in the burgeoning 50cc scooter market, characterized by its simplicity and affordability.
Production Period:
1979 to 1992
Manufacturing Location:
Likely manufactured in Japan or other Yamaha overseas facilities.
