Vehicle Class:
Lightweight Scooter / Moped
Target Audience:
Commuters, hobbyists, restoration enthusiasts
Competitors:
Honda Spree, Tomos A3, Sachs MadAss (period competitors in lightweight segment)
Vehicle Highlights:
Lightweight, economical, simple to operate and maintain, iconic 80s/90s scooter design
Primary Coverage:
Full Service and Repair
Specific Component Coverage:
Includes detailed coverage of carburetor, ignition system (CDI, coil), CVT, brakes, suspension, electricals, frame, and bodywork.
Type:
Workshop Manual / Service Manual
Format:
Digital (Likely PDF)
Engine:
Complete engine disassembly, assembly, tuning, and troubleshooting
Fuel System:
Carburetor adjustment, cleaning, rebuilding; fuel tank and lines
Ignition System:
Spark plug, ignition coil, CDI unit diagnostics and replacement
Transmission:
Automatic transmission (CVT) inspection, maintenance, and repair
Brakes:
Front and rear brake system maintenance, adjustments, and component replacement
Electrical System:
Wiring diagrams, lighting, battery, charging system, starting system
Suspension Steering:
Front fork, rear shock absorber, steering system maintenance and adjustment
Cooling System:
Air-cooled engine, focus on cylinder and head cooling fins
Frame Bodywork:
Chassis inspection, body panel removal and installation
Maintenance:
Scheduled maintenance, oil changes, filter replacements, lubrication
Troubleshooting:
Diagnostic charts for common problems and their solutions
Repair:
Step-by-step repair instructions for all major components
Rebuilding:
Detailed instructions for engine and transmission rebuilds
Refurbishment Restoration:
Guidance on restoring the vehicle to original specifications
Wiring Diagrams:
Detailed electrical system wiring diagrams included for troubleshooting and repair.
Engine Tuning:
Includes procedures for carburetor jetting and timing adjustments for optimal performance.
Depth:
Comprehensive (from basic checks to full rebuilds)
Specifications Tables:
Includes detailed torque specifications, clearances, and measurement data for all components.
Diagnostic Procedures:
Step-by-step diagnostic guides for common malfunctions.
Engine Type:
2-stroke, air-cooled, single-cylinder
Displacement:
49cc (49 cubic centimeters)
Bore X Stroke:
Approx. 39.0mm x 41.4mm
Compression Ratio:
Approx. 6.7:1
Carburetor Model:
Mikuni VM14SC (typical for this application)
Spark Plug Type:
NGK BR7HS or equivalent
Engine Cooling:
Forced Air Cooling
Horsepower:
Approx. 3.5 - 4.5 PS (at specified RPM)
Torque:
Data not readily available, typically low for 49cc
Fuel Type:
Unleaded gasoline (mixed with 2-stroke oil)
Fuel Oil Mix Ratio:
Typically 50:1 or 100:1 depending on oil quality (refer to manual for exact spec)
Fuel Tank Capacity:
Approx. 3.2 Liters (0.85 US gallons)
Overall Length:
Approx. 1600 mm (63 inches)
Overall Width:
Approx. 660 mm (26 inches)
Overall Height:
Approx. 970 mm (38.2 inches)
Wheelbase:
Approx. 1150 mm (45.3 inches)
Dry Weight:
Approx. 70 kg (154 lbs)
Gross Vehicle Weight Rating:
Approx. 220 kg (485 lbs) (including rider and cargo)
Storage Compartment:
Under-seat storage (limited)
Crash Test Data:
Not applicable for this vehicle type and era
Brakes:
Drum brakes front and rear
Lighting:
Headlight, taillight, brake light, turn signals
Chassis Design:
Steel tube frame for rigidity
Oil Change:
Every 1,000 km or 6 months (engine oil, typically 10W-30 or 10W-40)
Spark Plug Check Replace:
Every 1,000 km or annually
Air Filter Cleaning Replacement:
Every 1,000 km for cleaning, replacement as needed (refer to manual)
Carburetor Adjustment:
As needed, or every 2,000 km for optimal performance
Engine Oil Type:
SAE 10W-30 or 10W-40 API SE or SF classification (confirm with manual)
Engine Oil Capacity:
Approx. 0.6 Liters (0.63 US quarts)
Brake Fluid Type:
DOT 3 or DOT 4 (for hydraulic brake systems, if equipped)
Gearbox Oil:
N/A (CVT system does not have a separate gearbox oil fill)
Common Problems:
Carburetor gumming (especially if left unused), weak ignition coil, CVT belt wear, general wear and tear on suspension and brakes due to age.
Starting Issues:
Often related to fuel delivery (clogged carb/filter), weak spark, or compression loss.
Performance Degradation:
Can be caused by worn CVT components, incorrect fuel/oil mixture, or carbon buildup in the exhaust port.
Yamaha History:
Yamaha Corporation, founded in 1887, known for musical instruments and later motorbikes and engines. Yamaha Motor Company spun off in 1955 and has a strong reputation for quality and performance in motorsports and recreational vehicles.
Qt50 Lineage:
The QT50 was part of Yamaha's line of lightweight scooters, popular in the 1980s and early 1990s for their ease of use and fuel efficiency. It followed models like the QT50 and preceded later designs.
Production Years:
Mid-1980s to early 1990s (exact start/end dates vary by market)
Manufacturing Location:
Primarily Japan, but some components or assembly may have occurred elsewhere depending on market distribution.
