1986-1988 Yamaha Moto-4 225 YFM Service & Repair Manual (OEM)

• Official 251-page OEM publication for the 1986–1988 Yamaha YFM 225 Moto-4 (P/N prefix 59V, JY459V serial range)
• Covers the 2WD chassis, fuel-delivery, electrical components, and complete engine systems
• Features 47 exploded-view diagrams, 8 detailed torque specification tables, and 17 specialized tool references
• Serves as the authoritative factory reference for transmission and internal tolerances on the 59V-series build

Documentation Walkthrough

When tearing down a machine in the shop, having accurate factory specs is essential. This guide outlines the entire architecture of the ATV, starting with general vehicle identification and periodic inspection schedules. From there, it moves directly into engine overhaul procedures, carburetor tuning, chassis maintenance, and electrical system diagnostics. Appendices at the back provide quick reference points for major operations, including precise gear lash settings and component clearances needed for proper reassembly.

Engine and Chassis Specifications

Technical documentation gives mechanics the exact numbers required for a reliable rebuild. For instance, the YFM 225 requires a strict 1,400 ± 50 rpm idle speed. You will find the correct torque values for cylinder head bolts, oil pumps, and crankcase screws directly from the manufacturer. Intake valve clearances are documented at 0.05–0.09 mm, with standard sea-level compression pressure rated at 883 kPa. The technical data section even specifies the 0.6–0.7 mm spark plug gap. Because working on ATVs involves heavy machinery and combustible systems, there are inherent safety risks. Always consult the full factory data and observe proper workshop safety protocols before beginning any hands-on maintenance. The figures mentioned here offer just a glimpse of the internal tolerances covered in the complete document.