Vehicle Type:
Lightweight scooter designed for urban commuting and recreational use.
Target Audience:
Young riders, commuters, those seeking economical transportation.
Competitors Era:
Competed with other 50cc scooters from brands like Honda (e.g., Spree, Aero), Suzuki (e.g., AY50), and Tomos during the late 1980s.
Design Philosophy:
Emphasis on simplicity, reliability, and fuel efficiency in a compact package.
Standout Attributes:
Lightweight construction, easy operation, characteristic Yamaha build quality for its class.
General Coverage:
Comprehensive repair and service for the 1987 Yamaha QT50 scooter.
Specific Systems Covered:
Engine, transmission, fuel system, electrical system, braking system, suspension, chassis, bodywork, and routine maintenance.
Estimated Page Count:
Varies by specific edition, typically 150-300 pages for a full repair manual.
Manual Type:
Repair Service Manual
Engine Systems:
Top-end overhaul (cylinder, piston, rings), crankshaft, bearings, seals, cooling system (air-cooled), lubrication.
Fuel System:
Carburetor disassembly, cleaning, adjustment, fuel tank, fuel lines, fuel filter replacement.
Transmission Drivetrain:
Automatic transmission (V-belt type), clutch, variator operation, final drive (chain/gear). Specific details on variator belt inspection and replacement.
Electrical System:
Ignition system (CDI), lighting (headlight, taillight, signals), battery charging system (alternator/stator), starting system, wiring diagrams, fuse locations, troubleshooting electrical faults.
Braking System:
Front and rear drum brake operation, adjustment, shoe replacement, linkage maintenance.
Suspension Steering:
Front fork assembly (oil change, seal replacement), rear shock absorber, steering head bearings, linkage lubrication.
Chassis Bodywork:
Frame inspection, body panel removal and installation, seat removal, footrest assembly, handle grip replacement.
Routine Maintenance:
Oil change intervals and specifications, spark plug replacement, air filter cleaning/replacement, brake adjustment, chain lubrication (if applicable to final drive), tire pressure checks.
Troubleshooting:
Systematic diagnostic procedures for common starting issues, poor running conditions, electrical faults, and braking problems.
Major Repairs:
Complete engine rebuild, transmission overhaul, fork seal replacement, carburetor rebuilding, electrical component testing and replacement.
Special Tools:
Identification of required special tools for specific procedures (e.g., flywheel puller, clutch holder).
Depth Of Information:
Designed for professional technicians, offering detailed specifications, diagnostic trees, and step-by-step repair instructions.
Diagnostic Capabilities:
Covers common issues and their causes, enabling diagnosis of performance problems and component failures.
Rebuild Procedures:
Detailed instructions for complete disassembly, inspection, repair, and reassembly of major components like the engine and transmission.
Engine Type:
2-stroke, air-cooled, single-cylinder
Bore X Stroke:
37.0 mm x 44.0 mm (Typical for this class)
Compression Ratio:
Approx. 7.0:1 (Typical for this class)
Intake System:
Reed valve induction
Horsepower Est:
Approx. 3.5 - 4.5 HP (At flywheel, dependent on tuning and regulations)
Torque Est:
Approx. 3.0 - 3.5 Nm (At flywheel, dependent on tuning and regulations)
Carburetor Model:
Yamaha specific, likely a Mikuni VM series or similar (e.g., VM12)
Fuel Type:
Unleaded gasoline (typically 87 octane or higher)
Oil Mixing:
Pre-mix or Autolube system (depending on specific QT50 variant, Autolube is common for this era Yamaha).
Length Overall:
Approx. 1640 mm (5 ft 4.6 in)
Width Overall:
Approx. 670 mm (2 ft 2.4 in)
Height Overall:
Approx. 995 mm (3 ft 3.2 in)
Wheelbase:
Approx. 1170 mm (3 ft 10.1 in)
Dry Weight:
Approx. 64 kg (141 lbs)
Gross Vehicle Weight Rating:
Not specified, but typically around 150-200 kg including rider and cargo.
Safety Ratings:
N/A (Scooters of this era were not subject to the same automotive safety rating standards).
Braking System:
Drum brakes front and rear for controlled stopping.
Lighting:
Headlight, taillight, brake light, turn signals for visibility and signaling.
Frame Construction:
Steel frame providing structural integrity.
Oil Change Interval:
Every 1000-1500 km or annually (for gear oil in final drive). Engine oil for 2-stroke is mixed with fuel or in a separate oil reservoir.
Spark Plug Replacement:
Every 3000-5000 km or as needed based on condition.
Air Filter Maintenance:
Clean every 1000 km, replace as needed.
Brake Adjustment:
As needed, typically every 2000 km or if lever free play increases.
2 Stroke Oil Type:
High-quality 2-stroke engine oil, API TC or JASO FB/FC rated.
Final Drive Gear Oil:
Yamalube SAE 80W API GL-4 or equivalent.
Brake Fluid:
DOT 3 or DOT 4 (if applicable, typically not hydraulic on QT50).
Carburetor Clogging:
Common due to infrequent use and stale fuel, leading to starting problems or poor idling.
Variator Belt Wear:
Belts can wear over time, causing slipping, reduced acceleration, or inability to engage properly.
Electrical Connections:
Corrosion or loose connections in wiring harness, especially at grounds and connectors, can cause intermittent electrical issues.
Air Cooled Engine Overheating:
Can occur with prolonged heavy load or if cooling fins are obstructed by dirt/debris.
Yamaha Motorcycle History:
Yamaha Motor Company, founded in 1955, has a rich heritage in motorcycle and scooter manufacturing, known for innovation and performance.
Qt50 Lineage:
The QT50 was part of Yamaha's series of lightweight, user-friendly scooters aimed at the entry-level market. It followed earlier models and contributed to Yamaha's presence in the burgeoning scooter segment.
Production Period:
The QT50 was primarily produced in the 1980s, with the 1987 model being a representative example of its generation.
Manufacturing Location:
Typically manufactured in Japan or Southeast Asia by Yamaha Motor Corporation.
