1986–1988 Yamaha Moto-4 225 YFM Service & Repair Manual (P/N Lit116160483)

• Factory service information in a 251-page PDF for the Yamaha YFM225S Moto-4, model code 59V, covering the 2WD chassis and air-cooled SOHC engine.
• Engine overhaul covers removal, crankcase separation, cylinder head repair, and reassembly.
• Primary and secondary clutch service accompanies main transmission and sub transmission disassembly, inspection, and assembly.
• Middle gear and final drive repair sections detail drive axle positioning, shim selection, gear lash adjustment, and ring gear thrust clearance checks.
• Mikuni VM24SH carburetor procedures cover component inspection, float height adjustment, fuel level measurement, and idle speed adjustment.
• Chassis work includes front drum and rear disc brake service, rear axle bearing replacement, steering repair, and suspension inspection.
• Electrical fault tracing covers starting, charging, CDI ignition, lighting, and the auxiliary DC terminal, with circuit diagrams and troubleshooting charts.

Model Identification and Workshop Use

The manual starts with general vehicle identification and periodic inspection schedules. It is suited to mechanics with experience rebuilding engines and access to precision measuring equipment and a hydraulic press.

The identification section lists starting VIN *JY459V GC000101 and engine starting number 59V-000101**. The PDF contains 250 pages of YFM225S service material, including the wiring diagram, followed by one additional “Sub Transmission” page.

Engine and Transmission Repair

Engine procedures address rocker arm and camshaft inspection, valve guide replacement, valve seat reconditioning, and piston, ring, and crankshaft checks. Rebuild coverage extends to cam timing, the automatic cam chain tensioner, balancer gear alignment, and oil pump inspection.

The drivetrain uses a wet centrifugal clutch and a constant-mesh, dual-range five-speed transmission with reverse. Separate Transmission and Sub Transmission exploded views show the gear and shaft assemblies. The accompanying text covers shift fork and shift cam inspection, engagement dog wear, and operational checks during assembly.

Shaft Drive Diagnosis and Setup

The shaft drive troubleshooting chart links noise, jerky operation, and loss of drive to possible bearing, gear, or shaft faults. Setup procedures explain ring gear shim and thrust washer selection after housing or bearing replacement.

The middle gear section warns that overtightening the bearing housing during setup can reduce gear lash enough to damage the gear teeth.

Carburetor and Chassis Service

The carburetor specifications identify the 59V00 marking. A sectional view traces air, fuel, and mixture passages, while the service text addresses the needle valve, throttle slide, starter plunger, and jets.

Toe-in adjustment, front lower arm bushing checks, and swingarm pivot bearing inspection are covered in the chassis chapter. Rear shock service covers inspection, replacement, spring preload adjustment, and handling and disposal of the pressurized unit. Internal damper rebuilding is not covered.

Electrical Diagnostics

The YFM225S Wiring Diagram provides wire colors and connector layouts. Starting-system tests cover the neutral interlock, starter relay, cut-off relay, and starter motor internals. Ignition diagnosis includes coil resistance and spark gap testing; charging checks address the stator and regulator/rectifier.

The charging chapter explains how disconnecting the battery while the generator is running can damage the system’s semiconductors.

Specifications and Special Tools

Appendices provide intake and exhaust valve clearances, compression-test data, spark plug specifications, fluid capacities, and wear limits. Electrical test values support component diagnosis. Engine and chassis torque tables include cylinder head bolts, oil pump screws, and crankcase screws. The lubrication diagram and cable routing illustrations support reassembly.

Special tool references identify the crankcase separating tool YU-01135 and fuel level gauge YM-01312-A. Gear-lash measurement calls for tool YM-01230 with dial gauge YU-03097.

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.