1987–1999 Yamaha Moto-4 350 YFM350ERT / YFM350ERU / YFM350ERW ATV Service Manual Set

The base manual supplies the main repair procedures. The supplements provide model-specific changes, including ERU oil-temperature warning diagnosis and ERW chassis revisions; the ERW instructions refer back to the ERT procedures where applicable.

Bookmarks, Text Search and Wiring Detail

Navigation and small labels: Embedded PDF bookmarks provide access to the base chapters and both supplements. PDF text search is not available. Small connector and wire-color labels in the ERT and ERU wiring diagrams require zooming.

The three publications are combined in one printable, 294-page PDF. That total includes the symbol guide and index pages, two memo pages, and three otherwise blank pages.

Engine Overhaul, Shaft Drive and Electrical Testing

These selected service topics outline the repair coverage rather than reproduce the full contents. Other subjects include headlight beam adjustment and auxiliary DC terminal troubleshooting.

• Engine overhaul: Step-by-step procedures for engine removal, cylinder-head disassembly, piston inspection, crankcase separation, transmission inspection, and reassembly.

• Clutch and middle gear: Primary and secondary clutch service, recoil starter repair, balancer drive inspection, middle-gear shim selection, and gear-lash adjustment.

• Carburetion: BTM32SH carburetor disassembly, component inspection, float-height and fuel-level adjustment, plus a sectional view of its metering systems.

• Brakes and steering: Front drum and rear disc brake service, steering-shaft inspection, knuckle and tie-rod repair, and toe-in adjustment.

• Shaft drive and suspension: Final-drive gear overhaul, rear axle bearing replacement, swingarm inspection, and front and rear shock absorber checks.

• Electrical diagnosis: Starting-interlock, charging, CDI ignition, lighting, and indicator-system tests, with circuit diagrams and fault-finding charts.

This material is suited to technicians familiar with ATV service and equipped for electrical testing, precision measurement, and internal engine work.

Maintenance and Internal Engine Repair

The manual outlines factory procedures for periodic inspections, including valve clearance adjustments, throttle lever adjustment, and ignition timing verification. Its maintenance chart identifies work recommended for a Yamaha dealer.

For deeper powertrain repair, the document provides component limits and clearance specifications for the cylinder head, clutch assemblies, and transmission. Valve-seat drawings support the resurfacing instructions, while cam-sprocket timing illustrations accompany cylinder-head installation.

Tool callouts, including the YM-01404 flywheel puller and YM-04019 valve spring compressor, identify equipment needed before disassembly. Lubrication diagrams trace the oil pump, oil cooler, and internal feeds; cable-routing views show the placement of harnesses, hoses, and selector cables.

Gear Positioning and Chassis Revisions

The shaft-drive troubleshooting chart connects hesitation, unusual noise, and loss of drive with possible bearing, gear-lash, and gear-tooth faults. This helps distinguish driveline symptoms from engine surging before selecting component inspections.

Middle-gear and final-drive procedures cover shim calculations, gear positioning, and ring-gear thrust-clearance checks. The middle-gear section warns that overtightening the bearing-housing bolts can reduce gear lash enough to damage the gears.

The ERW supplement changes the front brake seal installation and rear axle nut procedure relative to the ERT instructions. Its carburetor and suspension tables provide additional model-specific reference data.

Starting Interlocks and Oil-Temperature Diagnosis

The starting-circuit diagram explains the relationship between the starter relay, cut-off relay, neutral and reverse circuits, and brake switch. The accompanying no-crank charts provide component and connection checks rather than treating every starting problem as a starter-motor fault.

For the ERU, display-system testing distinguishes bulb, socket, and indicator-checker faults from thermo-relay and thermo-switch problems. Separate ERT and ERU wiring diagrams show the relevant connector arrangements and wire-color codes.

Always prioritize shop safety. Verify torque figures and procedures against the applicable manual section before service, particularly when supporting the ATV or handling the pressurized rear shock absorber.

Examples of Engine Fastener and Charging Data

The YFM350ERT engine sections specify 10 Nm for the tappet covers and 7 Nm for the oil gallery bolt. The accompanying procedures connect these component-specific figures to valve service and oil-flow inspection.

The base charging-system chart specifies 14–15 V at 5,000 r/min, with a separate charging-coil resistance test for fault isolation.