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Yamaha QT50 QT 50 1985 Repair Service Manual

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🏷️ Basic Information Identification Make: Yamaha Model: QT50 Year: 1985 Type: Moped / Scooter Codes Chassis Code: QT50-XXXXXX Engine Code: A170E 👋 Introduction Market Position Historical Context: The Yamaha QT50...

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斯库: 394039

标签: 1985 Motorcycle Motorcycles QT 50 QT50 QT50 MA50 Yamaha

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Description

🏷️ Basic Information

Identification

Make:

Yamaha

Model:

QT50

Year:

1985

Type:

Moped / Scooter

Codes

Chassis Code:

QT50-XXXXXX

Engine Code:

A170E

👋 Introduction

Market Position

Historical Context:

The Yamaha QT50 was a popular lightweight, air-cooled, two-stroke moped targeted at urban commuting and recreational use in the 1980s.

Competitive Analysis

Competitors:

Competed with similar models from Honda (e.g., Hobbit, Spree), Suzuki (e.g., FA50), and Tomos.

Key Features

Features:

Compact size, easy operation, fuel efficiency, simple maintenance, distinctive styling for its era.

Value Proposition

Manual Value:

Provides essential technical data for restoring and maintaining the classic Yamaha QT50, ensuring longevity and correct operation.

📋 Manual Details

Coverage Areas

Primary Coverage:

Comprehensive repair and service procedures for the 1985 Yamaha QT50.

Secondary Coverage:

Maintenance schedules, troubleshooting guides, electrical diagrams, torque specifications.

Page Count

Estimated Page Count:

100-200

Manual Type

Type:

Repair Service Manual

Target Audience:

Professional Technicians and Experienced DIY Mechanics

Language

Language:

English

Format

Format:

PDF Download

📖 Manual Coverage

Systems Covered

Engine:

Disassembly, assembly, inspection, troubleshooting, carburetor tuning, cooling system.

Fuel System:

Fuel tank, fuel lines, fuel filter, carburetor (VM12SC) servicing and adjustment.

Ignition System:

CDI ignition, spark plug, ignition timing, troubleshooting.

Transmission:

Automatic V-belt drive system (CVT), torque converter, clutch, variator inspection and service.

Brakes:

Front and rear drum brake system, brake shoe replacement, brake cable adjustment.

Suspension:

Front telescopic fork, rear monoshock absorber, fork oil replacement, shock absorber inspection.

Electrical System:

Wiring diagram, lighting system, horn, starter system (kick start), battery maintenance, fuse replacement.

Frame And Body:

Chassis components, seat, handlebars, fenders, body panel removal and installation.

Procedures Included

Maintenance:

Routine checks, lubrication points, filter changes, spark plug replacement.

Troubleshooting:

Diagnosis of common problems, fault finding charts, diagnostic flowcharts.

Repair:

Detailed step-by-step instructions for component disassembly, repair, and reassembly.

Adjustment:

Carburetor idle speed, throttle cable, brake cables, parking brake.

Specifications:

Torque values for all fasteners, engine clearances, fluid capacities.

Technical Depth

Depth:

Comprehensive, covering full rebuilds and advanced diagnostics.

📊 Manual Specifications

File Format

Format:

Digital (PDF)

Searchability:

Likely text-searchable (depending on original scan quality)

Print Quality

Quality:

Digital reproduction; clarity depends on original source.

Binding Type

Binding:

Not applicable (Digital PDF)

Paper Type

Paper:

Not applicable (Digital PDF)

⚙️ Engine Specifications

Primary Engine

Engine Type:

2-stroke, air-cooled, reed valve induction

Displacement:

49cc (49 cm³)

Bore X Stroke:

38.0 mm x 43.0 mm

Compression Ratio:

6.2:1

Carburetor Model:

Mikuni VM12SC

Carburetor Settings:

Idle speed: 1400-1600 rpm; Pilot jet: #17.5; Main jet: #75; Needle: 4J12-3 (2nd clip from top); Air screw: 1.5 turns out from seated.

Performance

Horsepower Approximate:

Approx. 3.5 - 4.0 HP @ 6500 RPM

Torque Approximate:

Approx. 3.0-3.5 Nm @ 5500 RPM

Fuel System

Fuel Type:

Unleaded gasoline, 87 octane (minimum)

Oil Mixing Ratio:

100:1 (Yamalube 2-stroke oil or equivalent) for premix, or via automatic oil injection system.

Fuel Tank Capacity:

2.5 Liters (0.66 US gallons)

Ignition System

Ignition System Type:

CDI (Capacitor Discharge Ignition)

Spark Plug Type:

NGK B7HS or equivalent

Spark Plug Gap:

0.6 - 0.7 mm (0.024 - 0.028 in)

Ignition Timing:

13° BTDC @ 2000 RPM (static)

🔧 Transmission

Standard

Transmission Type:

Automatic V-belt drive system (CVT - Continuously Variable Transmission)

Drive System:

Shaft drive (from transmission output to rear wheel)

Features

Clutch Type:

Centrifugal clutch

Variator Type:

Torque converter type with movable drive and driven sheaves.

Gear Ratios:

Variable (2.53 - 0.86)

Transmission Oil Type:

Yamaha Gear Oil GL-4 SAE 80W

Transmission Oil Capacity:

0.1 Liters (0.03 US quarts)

📐 Dimensions

Exterior

Length:

1,640 mm (64.6 in)

Width:

670 mm (26.4 in)

Height:

995 mm (39.2 in)

Wheelbase:

1,165 mm (45.9 in)

Weights

Dry Weight:

57 kg (126 lbs)

Wet Weight:

61 kg (135 lbs) (approximate with full fluids)

Wheels And Tires

Front Tire Size:

2.50-16 4PR

Rear Tire Size:

2.50-16 4PR

Front Tire Pressure:

200 kPa (2.0 kgf/cm², 29 psi)

Rear Tire Pressure:

225 kPa (2.3 kgf/cm², 33 psi)

Wheel Type:

Spoked wheels with aluminum rims

🛡️ Safety Features

Ratings

Safety Rating:

Not applicable for this class of vehicle in its era; relies on basic design for rider protection.

Active Features

Braking System:

Front and rear drum brakes.

Lighting:

Headlight, taillight, brake light, turn signals, position lights.

Passive Features

Frame Construction:

Steel tube frame for structural integrity.

Rider Controls:

Handlebar mounted controls for throttle, brakes, and lights.

💡 Technology Features

Infotainment

Features:

Basic instrumentation: speedometer, odometer, indicator lights (turn signal, high beam).

Driver Assistance

Features:

None (vehicle from an era predating modern driver assistance systems).

Connectivity

Features:

None.

🔧 Maintenance

Service Intervals

Oil Change Transmission:

Every 3,000 km (1,800 miles) or annually.

Spark Plug Cleaning And Gap Check:

Every 1,000 km (600 miles).

Air Filter Cleaning:

Every 1,000 km (600 miles); replace if damaged.

Carburetor Cleaning:

As needed, or every 3,000 km (1,800 miles) for optimal performance.

Brake Adjustment:

Every 2,000 km (1,200 miles) or as needed.

Fluid Specifications

Transmission Oil:

Yamaha Gear Oil GL-4 SAE 80W or equivalent.

Fork Oil:

Approximately 10W fork oil (specific volume to be confirmed in manual, typically ~100-150ml per leg).

Fuel Mixture Oil:

Yamalube 2-stroke oil or API TC classified oil (100:1 ratio recommended).

Known Issues

Common Problems:

Carburetor gumming from old fuel, worn drive belt, ignition system (CDI) failures, worn brake shoes, fork seal leaks.

Troubleshooting Tip Carburetor:

Ensure correct pilot jet and needle setting for clean idle and smooth acceleration. Check for vacuum leaks on intake manifold.

Troubleshooting Tip Drive Belt:

Inspect for cracking, fraying, or excessive wear. Replace if width is reduced or if slippage occurs under load.

📚 Vehicle History

Brand Heritage

Brand Focus:

Yamaha Motor Company, renowned for its motorcycles, musical instruments, and marine products, has a long history of innovation in engine technology.

Model Evolution

Predecessors:

The QT50 built upon Yamaha's experience with small-displacement, two-stroke engines and automatic transmissions in earlier moped designs.

Successor Models:

Yamaha continued to produce various moped and scooter models, evolving engine technology and chassis designs over the years.

Production

Production Period:

Mid-1980s (specifically 1985 model year covered by manual).

Manufacturing Location:

Likely Japan, though specific assembly locations could vary.

🏆 Awards & Recognition

Recognitions

Historical Acclaim:

While specific awards are unlikely, the QT50 was recognized for its reliability and ease of use within the moped market segment of its time.

Ratings

Consumer Satisfaction:

Generally positive for its intended use as an affordable and practical urban transport.