Yamaha ET250 & Enticer 250 (1984) Snowmobile Service Manual: Comprehensive Maintenance, Repair, and Parts Guide

Yamaha ET250 Service Manual - 1984

This professional service manual provides the definitive engineering data required for the maintenance and overhaul of the Yamaha ET250 series. It integrates a critical lubrication protocol requiring the application of low-temperature lithium soap base grease to the oil seal lips during installation, which is vital for maintaining vacuum integrity and preventing lean-run engine seizures in sub-zero operational environments.

Technical Applicability & Machine Identification

The specifications and procedures contained herein apply to the following chassis and engine configurations, identified by the primary model prefix:

• 84G Series (Chassis & Engine ID Prefix)
  • Yamaha ET250 (1984)
  • Yamaha Enticer 250 (1984)
  • Yamaha ET Series (Applicable to 250cc Technical Variant)

Operational Reliability & Precision Standards

• System Integrity: Factory-mandated replacement of all gaskets, oil seals, O-rings, and lock washers during overhaul ensures long-term fluid retention and structural safety.
• Component Longevity: Specific "mated part" tracking requirements for gears, cylinders, and pistons prevent accelerated wear patterns and mechanical disharmony.
• Service Accuracy: Usage of model-specific tools, such as the Primary Sheave Puller (M20) and Dial Gauge Stand, ensures components are serviced to factory tolerances without risk of deformation.

Technical Document Metadata

• Document Type: Service Manual
• Technical Series: ET250
• Starting Serial Number: 84G-000101
• Format: Digital Technical Publication

Technical Depth & Factory Benchmarks

Technical personnel must adhere to these baseline calibration data points to maintain factory performance levels:

• Ignition Timing (B.T.D.C.): 1.6 ± 0.1 mm (0.063 ± 0.004 in).
• Engine Idle Speed: 1,600 ± 100 r/min.
• Cylinder Bore Standard: 60.00 mm (2.362 in).
• Piston Clearance: 0.040–0.045 mm (0.0016–0.0018 in).

Diagnostic & System Schematics

This manual utilizes a standardized "Illustrated Symbol" navigation system for rapid identification of lubrication points, tightening requirements, and sealing agents. Technical illustrations include:

• Gear Train Architecture: Detailed power transmission routes for both Forward and Reverse gear systems.
• Carburetor Fuel Flow: Visual mapping of fuel/air mixture paths through the pilot and main circuits.
• Exploded View Assemblies: Component-level breakdowns for the recoil starter, oil pump drive gear, and secondary shaft.

Table of Contents

• Chapter 1: General Information (Machine ID, Special Tools, Storage)
• Chapter 2: Periodic Inspections and Adjustments (Maintenance Table, Engine, Power Train, Chassis, Electrical)
• Chapter 3: Engine Overhaul (Removal, Disassembly, Inspection, Assembly, Recoil Starter)
• Chapter 4: Carburetion (Disassembly, Inspection, Tuning, High Altitude Adjustments)
• Chapter 5: Power Train (Primary/Secondary Sheaves, Drive Chain, Brake, Slide Rail)
• Chapter 6: Chassis (Ski, Steering, Fuel Tank)
• Chapter 7: Electrical (Ignition System, Lighting, Switches)
• Chapter 8: Appendices (Specifications, Tightening Torque, Cable Routing)

Operational Limits & Fluid Specifications

Strict adherence to fluid grades is required to maintain the warranty and operational safety:

• Engine Lubrication: YAMALUBE 2-cycle oil (Capacity: 2.4 L).
• Drive Chain Housing: Gear oil API GL-3, SAE #75 or #80 (Capacity: 0.3 L).
• Lubrication Points: Esso-Beacon 325 or Aero Shell grease #7 for bearings; Molybdenum disulfide grease for secondary shafts.
• Torque Sequence: Cylinder head nuts must be tightened in two stages, reaching a final torque of 25 Nm (18 ft-lb) in a crisscross pattern.