🏷️ Basic Information

Make:

Yamaha

Model:

QT50 QT 50

Year:

1986

Product Name:

Yamaha QT50 QT 50 1986 Full Service Repair Manual

Vehicle Chassis Code:

QT50

👋 Introduction

Vehicle Type:

The Yamaha QT50 QT 50 is a lightweight, 2-stroke, automatic scooter designed for economical urban commuting and recreational use.

Target Audience:

Appealed to riders seeking a simple, reliable, and fuel-efficient mode of transportation, often as a first vehicle or for short-distance travel.

Competitors:

Competed with other 50cc scooters and mopeds from manufacturers like Honda (e.g., Aero 50), Suzuki, and Tomos during its production era.

Ease Of Use:

Automatic transmission and simple controls made it very accessible to riders of all experience levels.

Fuel Efficiency:

As a 50cc 2-stroke, it offered excellent fuel economy.

Low Maintenance:

The 2-stroke engine, while requiring oil mixing, generally has fewer moving parts than a 4-stroke, contributing to simpler maintenance.

Value For Owner:

This manual empowers owners to perform a wide range of maintenance and repair tasks, saving money on labor costs and extending the lifespan of their vintage scooter.

📋 Manual Details

Manual Type:

Full Service Repair Manual

Page Count:

Detailed (Exact count not provided, but described as 'very detailed' and 'everything you will ever need')

Language:

English

Format:

Likely PDF or printed manual based on typical product offerings for this type of item.

📖 Manual Coverage

Engine Systems:

Comprehensive coverage of the 2-stroke engine, including disassembly, assembly, tuning, carburetion, lubrication, cooling, and ignition systems.

Transmission Drivetrain:

Detailed information on the automatic transmission (likely V-belt type), clutch, final drive, and associated components.

Brake Systems:

Service and repair procedures for front and rear braking mechanisms (likely drum brakes), including adjustment and component replacement.

Electrical Systems:

Wiring diagrams, troubleshooting for lighting, ignition, charging system, and other electrical components.

Suspension Steering:

Information on front fork, rear shock absorber, and steering system maintenance and repair.

Fuel System:

Carburetor tuning, fuel tank, fuel lines, and fuel filter service.

Cooling System:

Details on air cooling system for the 2-stroke engine.

Bodywork Frame:

Procedures for disassembly and reassembly of body panels, seat, handlebars, and frame inspection.

Maintenance Procedures:

Routine maintenance tasks such as oil changes (for gearbox), filter cleaning/replacement, spark plug inspection/replacement, brake adjustment, and chain lubrication/adjustment.

Troubleshooting:

Systematic diagnostic procedures to identify and resolve common problems and malfunctions.

Rebuild Overhaul:

Detailed instructions for complete engine disassembly, rebuilding, and reassembly, including critical component specifications.

Repair Replacement:

Step-by-step guidance for replacing worn or damaged parts across all major vehicle systems.

Calibration Adjustment:

Procedures for adjusting carburetor settings, brake levers, clutch, and other mechanical components.

Depth Level:

Comprehensive, covering everything from basic adjustments to complete engine and component overhauls. Suitable for both novice mechanics and experienced technicians.

📊 Manual Specifications

Digital Format:

Likely PDF, offering searchability and easy navigation if digital. If print, it would be bound pages.

Print Quality:

Expected to be high quality with clear diagrams and text, suitable for workshop use.

Binding Type:

If printed, likely coil-bound or comb-bound for lay-flat usability in a workshop environment, or a professional hard/soft cover binding.

Paper Type:

Durable paper stock suitable for repeated handling in a workshop setting.

⚙️ Engine Specifications

Engine Type:

2-stroke, air-cooled

Displacement:

49cc

Bore X Stroke:

37.0mm x 43.0mm (typical for this engine family)

Compression Ratio:

Approx. 7.0:1 (typical)

Cylinder Arrangement:

Single Cylinder

Engine Cooling:

Forced air cooling via fan and shrouding

Horsepower:

Approximately 3.0 - 4.0 HP at specific RPM (exact figures vary by tuning and market)

Torque:

Low-end torque optimized for initial acceleration.

Carburetor Model:

Likely a Mikuni VM series or similar, with specific model number detailed in the manual (e.g., VM14/14).

Fuel Mixture:

Requires pre-mix of gasoline and 2-stroke oil (typically 50:1 or 100:1 ratio specified in manual).

Ignition Type:

CDI (Capacitor Discharge Ignition)

Spark Plug Type:

Specific NGK or Champion plug type and gap (e.g., NGK BPR5HS, gap 0.6-0.7mm).

Gearbox Oil Type:

Specific SAE gear oil specification (e.g., SAE 80 or SAE 80W-90).

Engine Serial Number Location:

Typically stamped on the crankcase or cylinder base.

🔧 Transmission

Transmission Type:

Automatic (V-belt Continuously Variable Transmission - CVT).

Optional Transmissions:

None.

Clutch Type:

Centrifugal automatic clutch.

Drive Type:

Belt drive to rear wheel.

Cvt Belt Inspection:

Manual includes procedures for inspecting and replacing the V-belt for proper engagement and durability.

Gearbox Oil Capacity:

Specific oil capacity for the gearbox (e.g., 0.07 liters or 70cc).

📐 Dimensions

Overall Length:

Typically around 1500-1600 mm.

Overall Width:

Typically around 650-700 mm.

Overall Height:

Typically around 950-1000 mm.

Dry Weight:

Approximately 65-75 kg.

Gross Vehicle Weight Rating:

Specified in manual, considering rider and cargo.

Front Tire Size:

Typically 3.00-10 or 3.50-10.

Rear Tire Size:

Typically 3.00-10 or 3.50-10.

Wheel Type:

Steel wheels, likely 10-inch diameter.

Tire Pressure:

Specified in manual, usually around 17-25 PSI (front/rear).

🛡️ Safety Features

Safety Certification:

Designed to meet relevant safety standards for scooters of its era.

Braking System:

Front and rear drum brakes providing adequate stopping power for the vehicle's performance.

Lighting System:

Headlight, taillight, brake light, turn signals, and instrumentation lighting for visibility and signaling.

Chassis Design:

Underbone frame construction providing stability and rider ergonomics.

Horn:

Standard audible warning device.

💡 Technology Features

Dashboard Features:

Basic instrumentation including speedometer, odometer, and indicator lights (e.g., turn signals, high beam).

Assistance Systems:

None; this is a basic mechanical vehicle.

Connectivity Features:

None.

🔧 Maintenance

Oil Change Gearbox:

Recommended every 3,000-5,000 km or annually, detailed in manual.

Air Filter Cleaning:

Monthly or every 1,000 km, depending on operating conditions.

Spark Plug Check:

Every 1,000-2,000 km, or as needed.

Brake Adjustment:

Regular checks for free play, adjust as needed.

Cvt Belt Inspection:

Inspect every 5,000 km, replace as needed based on wear.

Gearbox Oil Spec:

API GL-3 or GL-4, SAE 80 or 80W-90 gear oil.

2 Stroke Oil Type:

Yamaha recommends its own 2M-Super Premium 2-stroke oil or equivalent API TC, JASO FB rated oil.

Carburetor Clogging:

Common with 2-stroke engines left sitting; manual provides cleaning and tuning procedures.

Cvt Belt Wear:

Belt can wear over time, leading to poor acceleration; manual covers inspection and replacement.

Ignition Coil Failure:

Can lead to no spark; manual offers troubleshooting steps.

Fuel Line Perishing:

Rubber fuel lines can degrade over time; manual guides replacement.

📚 Vehicle History

Yamaha Motor Corporation:

Yamaha Motor Corporation is a globally recognized manufacturer of motorcycles, marine products, and other motorized vehicles, known for quality and innovation.

Qt50 Lineage:

The QT50 was part of Yamaha's lineup of lightweight scooters, evolving from earlier models and paving the way for future scooter designs.

Production Period:

The QT50 was produced in the 1980s, with the 1986 model year being a significant iteration.

Manufacturing Location:

Likely manufactured in Japan or other Yamaha global facilities.

🏆 Awards & Recognition

Model Recognition:

The QT50 is recognized as a reliable and enduring example of 1980s Japanese scooter design.

Performance Ratings:

Praised for its simplicity, fuel economy, and ease of use in its class.

Certification Standards:

Manufactured to meet the safety and emissions standards of its time.