Yamaha QT50J, MA50 Yamahopper 1979-1992 Service & Repair Manual (P/N LIT-11626-02-97)

• Covers 1979–1992 Yamaha QT50J and MA50 Yamahopper variants, detailing mechanical inspections, engine overhauls, and chassis maintenance requirements.
• OEM Publication LIT-11626-02-97, documenting the original 1979 first edition service specifications.
• Features 47 pages of technical diagrams, factory color codes, exploded-view engine assemblies, and torque specification reference tables.
• This 2006 reissue of the factory manual serves as the primary technical reference for the QT50 series, breaking down critical systems like the Autolube oil pump and reed valve assembly.

Mechanical Systems and Maintenance Overview

This manual provides targeted technical data for the Yamaha QT50J and MA50 Yamahopper. It breaks down the 49cc 2-stroke engine, carburetion, transmission, and chassis components. Technicians will find exact factory documentation for air cleaner servicing, oil pump bleeding, and ignition timing verification. The guidelines outline the specific tolerances required to keep the 6V electrical system and autolube pump operating precisely. You also get a complete rundown of daily pre-operation checks covering brake performance, tire pressure, and fastener security. Working on fuel systems and older 2-stroke engine components carries inherent risks. Always verify your workspace ventilation and adhere to standard workshop safety protocols before initiating any diagnostic work or test rides.

Specifications and Reference Values

The documentation provides hard numbers for critical fasteners and engine components without relying on guesswork. The cylinder head nut torque is clearly listed at 10 Nm. Fluid capacities are mapped out exactly in the reference tables. The transmission requires 0.3 liters of oil, and the total fuel tank volume holds 2.3 liters. Tire pressures are specified at 18 psi for the front and 28 psi for the rear. For electrical troubleshooting, the reference material includes detailed pinouts and wiring schematics dedicated specifically to the 6V charging system.