1987–1995 Yamaha YFM350ER Moto 4 ATV Service & Repair Manual (P/N LIT-11616-05-38, LIT-11616-07-01)

• 661-page, two-PDF factory set for 1987-1995 Yamaha Moto-4 YFM350ER/YFM350ERT ATVs. The 327-page early-model volume contains a 1-page compiled cover, the 270-page YFM350ERT base manual, a 24-page YFM350ERU supplement, a 12-page YFM350ERW supplement, and a 20-page YFM350ERA supplement; the later YFM350ER (A-G) manual is 334 pages.
• Matches the 1YW, 2VA, 3HP, and 3HP2 builds to JY41YW00, JY42VAW0, and JY43HPW0 frame/VIN prefixes and their factory engine starting numbers, including the ERA break at LC024101 / 3HP-024101.
• Documents engine removal and remounting, cylinder-head and valve-train repair, piston and crankshaft inspection, crankcase splitting, transmission and shifter service, automatic clutch work, oil-pump service, cam-chain timing, and electric/recoil starter procedures where fitted.
• Details middle-gear and final-drive repair, including drive and driven pinion inspection, factory shim selection, ring-gear setup, gear-lash measurement and adjustment, drive-shaft service, rear-axle work, and shaft-drive fault diagnosis.
• Covers Mikuni carburetor removal, sectional-view reference, disassembly, inspection, assembly, installation, and fuel-level adjustment, along with front and rear brakes, steering, tie rods, lower arms, shock absorbers, swingarm, wheels, hubs, bearings, toe-in, and control-cable setup.
• Traces CDI ignition, starter cut-off, reverse and neutral interlocks, charging, lighting, signal, accessory, and oil-temperature indicator circuits with component tests, relay checks, starter-motor testing, and system-specific troubleshooting charts.
• Supplies exploded assembly views, wiring diagrams, circuit diagrams, cable-routing drawings, lubrication diagrams, special-tool callouts, torque tables, capacities, adjustment data, electrical test specifications, and inspection and wear limits.

Publication Structure and Model-Year Changes

The original YFM350ERT base publication is Yamaha literature number LIT-11616-05-38, first edition April 1986. The early-model PDF also contains the YFM350ERU supplement LIT-11616-06-44, the YFM350ERW supplement LIT-11616-06-65, and the YFM350ERA supplement LIT-11616-07-01. The separate later manual is LIT-11616-07-51, first edition June 1990. Its factory cover is labeled YFM350ER (A-G), while the internal title page identifies the ERA base issue; it is a full service manual rather than another short supplement.

The supplements document real production changes. ERU adds the oil-temperature display circuit and its dedicated test sequence. ERW revises front-wheel and rear-axle service and identifies the model-specific axle tool. ERA adds revised brake-control adjustments, cable routing, electrical data, and updated specifications. These sections help keep launch-build 1YW procedures separate from later 2VA and 3HP configurations before parts or repair methods are selected.

Repair and Diagnostic Depth

This factory material goes well beyond routine maintenance. Periodic service sections cover valve clearance, cam-chain tension, compression testing, ignition timing, carburetor and throttle adjustments, engine and final-drive lubrication, brake and clutch adjustment, steering and toe-in checks, suspension inspection, wheel bearings, and electrical checks. The engine is the air-cooled SOHC single-cylinder used in this model family; cooling-related coverage centers on oil flow, the oil cooler, and oil-temperature monitoring rather than a liquid-coolant system.

The overhaul chapters follow the engine from removal through top-end work, crankcase separation, internal transmission and clutch inspection, reassembly, timing, and final installation. The separate drive-train chapter treats the middle drive and final drive as measured gear assemblies, with pinion and ring-gear shim selection tied to dial-gauge lash checks rather than simple remove-and-replace instructions.

Factory cautions explain why the sequence matters. Forcing uneven crankcase separation can damage the case mating surfaces, while overtightening the middle-gear bearing housing during setup can create too little lash and quickly ruin the gear teeth.

Diagrams, Tools, and Factory Data

Useful visual references include the carburetor sectional view, middle-gear and final-drive exploded views, starting/charging/ignition/lighting circuit diagrams, the YFM350ERU oil-temperature display-system test chart, full YFM350ERT and YFM350ERA wiring diagrams, and model-specific cable-routing drawings. Special-tool references include the crankcase separating tool YU-01135 / 90890-01135, final-gear lash measurement tool YM-01231 / 90890-01231, rear-axle nut wrench YM-37132, and pocket tester YU-03112 / 90890-03112.

Specification sections provide component-specific torque data, approved lubricants and capacities, valve and ignition settings, carburetor data, clutch and transmission inspection limits, middle/final-gear setup charts, chassis wear limits, battery and charging specifications, coil resistance data, and general conversion and lubrication references. Revised figures remain tied to the applicable model section instead of being presented as one blanket specification for every year.

Securely support the ATV before wheel, axle, brake, suspension, or shaft-drive repair. Electrical and starter procedures should be performed with the battery isolated where the manual calls for it, and the manual's warnings for hot oil, spring-loaded parts, rotating assemblies, pullers, presses, and striking tools should be followed throughout the work.