1984 Yamaha ET250 / Enticer 250 Snowmobile Service Manual (P/N Lit126180103)

• 199-page PDF - 190 pages of ET340TRM workshop material, followed by a 9-page ET400TRN identification and specification supplement. ET340TRM coverage begins at frame and engine number 84G-000101; ET400TRN coverage begins at 85V-000101.
• Engine repair coverage includes in-chassis top-end access, complete engine removal, crankcase separation, crankshaft and piston inspection, cylinder service, Autolube pump and drive-gear setup, CDI magneto work, and recoil-starter overhaul.
• Fuel-system procedures cover the Mikuni B38-32 carburetor, float-height adjustment, diaphragm fuel-pump inspection, idle and cable settings, high-altitude tuning, main-jet selection, and low-, midrange-, and high-speed troubleshooting.
• Power-train service addresses drive-belt inspection, primary- and secondary-sheave disassembly, sheave alignment, brake overhaul, forward/reverse chain-housing repair, drive-chain adjustment, track removal, and front-axle inspection.
• Chassis work covers slide-rail suspension removal and rebuild, spring setup, track alignment and tension, skis, leaf-spring front suspension, steering linkage, toe-out, and cable and hose routing.
• Electrical diagnosis includes ET340TRM CDI ignition and lighting schematics, no-spark and lighting fault charts, coil and output testing, switch-continuity checks, optional grip-warmer data, and a full wiring diagram.
• Factory reference sections provide maintenance and lubrication schedules, storage and preseason preparation, special-tool callouts, assembly torque tables, capacities, wear limits, clearances, adjustment data, and electrical test specifications.

Model and Configuration Coverage

The core manual is for ET340TRM / model code 84G, not ET250. Its specification section describes a 337cc fan-cooled, twin-cylinder two-stroke with Yamaha Autolube, V-belt automatic drive, chain-and-gear secondary reduction, and factory reverse. The appended ET400TRN / model code 85V material identifies a 408cc engine and model-specific setup data, but it is a specification supplement rather than a second complete repair manual.

This workshop manual is suited to experienced snowmobile mechanics and advanced owners equipped to work from factory exploded views, measurement procedures, electrical tests, and special-tool references.

Factory Repair Depth

The engine chapter goes beyond routine service. It documents removal and remounting while also identifying cylinder-head, cylinder, piston, recoil-starter, oil-pump, CDI-magneto, carburetor, and primary-sheave work that can be performed with the engine in the chassis. Internal repair coverage includes crankcase separation, crankshaft and bearing inspection, cylinder and piston measurement, ring and pin checks, seal replacement, staged tightening sequences, and final cable, timing, sheave, and idle adjustments.

Tool callouts are tied to the relevant jobs. Examples include the YS-33274 sheave gauge, YS-01880 primary-sheave holder, YU-03097 dial gauge with YU-01256 stand, YU-03112 pocket tester, and YU-33261 coil tester.

Fuel, Drive, and Chassis Service

The Autolube section covers pump-cable adjustment, pump-stroke inspection and shim adjustment, and air bleeding after oil-system work. Carburetor repair is supported by a fuel-flow chart, float and needle-valve inspection, temperature/altitude jet selection, plug-color evaluation, and troubleshooting tables for hard starting, poor response, overflow, and power loss.

Power-train chapters show how the primary and secondary sheaves, brake, chain housing, forward/reverse gear train, slide-rail suspension, track, and drive axle come apart, what to inspect, and what must be adjusted after reassembly. The suspension material also provides front and rear spring-setting tables based on snow conditions, handling, straight-line stability, bumping, and ride comfort.

Diagrams, Diagnostics, and Repair Cautions

Useful visual references include the forward/reverse power-transmission route views, carburetor fuel-flow chart, high-altitude tuning flowchart and main-jet selection table, chain-housing exploded assembly, three cable-routing views, and the ET340TRM wiring diagram. Separate ignition and lighting fault charts lead into spark-gap, coil-resistance, lighting-output, and switch-continuity tests.

The manual treats the oil pump as a precision assembly that must not be disassembled; it also calls for bleeding after oil components or hoses have been disconnected or the tank has run empty. The carburetor chapter warns that operating without the intake silencer changes intake pressure, creates a lean mixture, and can cause severe engine damage.

When a test requires the drive track to rotate, the rear of the machine must be firmly supported with the track clear of the floor, and people must be kept away from the track and its discharge path.