1987–1990 Yamaha YFM350ER Moto-4 ATV Service Manual (P/N LIT-11616-06-01)

Factory service coverage for the 1987–1990 Yamaha YFM350ER Moto-4, combining the YFM350ERT base manual with YFM350ERU, YFM350ERW, and YFM350ERA supplements.

A 310-page PDF in English, supplied as one file.

• Engine repair: Engine removal and installation, top-end overhaul, crankcase separation, recoil starter rebuilds, and internal component inspection.

• Clutch and transmission: Primary and secondary clutch inspection, transmission main axle teardown, shift mechanism service, and assembly checks.

• Fuel and lubrication: Carburetor disassembly, fuel-level adjustment, oil pump inspection, and engine and final gear lubricant specifications.

• Shaft drive and chassis: Middle and final gear service, drive shaft inspection, steering repair, suspension service, and brake adjustment.

• Electrical diagnosis: CDI ignition, electric starting, charging-system tests, electrical troubleshooting charts, and model-specific wiring diagrams.

Suited to mechanics and experienced owners familiar with internal engine repair, precision measurements, and the special tools required for crankshaft and gear service.

Engine Repair and Maintenance

The engine is an air-cooled, single-cylinder SOHC four-stroke with an oil cooler. Lubrication diagrams show the oil circuit and cooler connections.

Top-end procedures cover rocker arm shaft extraction, valve seat recutting, and decompression cam inspection. Valve seat cutting schematics and crankshaft assembly views accompany the component instructions.

Timing and assembly: The engine chapter details CDI rotor disassembly, balancer drive gear servicing, and punch-mark alignment with the buffer boss. Automatic cam chain tensioner inspection, valve clearance adjustment, and compression pressure testing are also covered.

Inspection limits: Valve spring free length and clutch friction plate thickness limits help you assess which parts can be reused before reassembly. Component-specific torque tables include separate cylinder head fastener specifications.

Carburetor and Oil System Service

Whether you are rebuilding the top end or dialing in the carb, this technical manual provides factory procedures for your Moto-4. Fuel system coverage includes carburetor float level settings, throttle cable adjustment, and air filter maintenance.

The Mikuni BTM32SH carburetor sectional view shows the internal component arrangement. Oil pump clearances and fluid-capacity tables support lubrication-system service. Engine oil change quantities differ between the maintenance instructions and specification tables.

Clutch, Transmission, and Shaft Drive Repair

The drivetrain uses a wet centrifugal automatic clutch, dual-range transmission, and shaft final drive. Clutch service extends to friction plates, springs, and the secondary clutch, while the shift mechanism section documents shift cam segment alignment.

Middle driven gear lash measurement and shim selection receive dedicated coverage. The Shaft Drive Troubleshooting chart relates driveline symptoms to possible bearing, gear, and drive shaft faults.

The middle gear instructions warn that overtightening the bearing housing bolts can reduce gear lash and damage the gears.

Steering, Brakes, and Rear Axle

The chassis section covers steering system inspections, brake lever and pedal adjustments, and tire pressure specifications. Wheel bearings, rear axle removal, and suspension inspection are included.

The ERW supplement, model code 3HP, adds revised front brake service and rear axle nut procedures, including use of rear axle nut wrench YM-37132. The rear axle instructions identify direct hammer blows as a cause of thread and spline damage.

Ignition, Starting, and Model-Specific Electrical Tests

Electrical troubleshooting covers magneto pick-up coil resistance, fuse ratings, ignition timing verification, and starter motor inspection. Cable routing drawings and the starting-circuit cut-off schematic accompany the wiring diagrams.

The ERU supplement, model code 2VA, adds oil temperature warning circuit diagnosis, including thermo switch and thermo relay tests. The ERA supplement, model code 3HP2, supplies revised CDI, ignition coil, and charging-system specifications; these distinctions help match electrical tests to the installed components.

Before turning wrenches on the engine, brakes, or shaft drive, ensure you have the proper tools and mechanical background to work safely; improper maintenance can cause equipment damage or injury.

PDF Navigation and Included Supplements

The file contains 266 pages of base-manual material, plus ERU, ERW, and ERA supplements of 20, 8, and 16 pages respectively. All 44 supplement pages, three blank pages, and three memo pages are already included in the 310-page total; the blank and memo pages also count within the individual sections.

PDF text search is not available. Embedded bookmarks provide navigation through the base manual and supplements, while small labels in the wiring diagrams require zooming.