1986 Honda 250 Engine Parts Manual

The 1986 Honda 250 Engine Parts Manual provides comprehensive information for the maintenance, repair, and replacement of engine components for the 1986 Honda 250 series. This manual covers engine specifications, part numbers, assembly procedures, torque specifications, and maintenance schedules for optimal performance and longevity.

1. Engine Specifications 2. Major Components Overview 3. Cylinder Head Assembly 4. Piston and Crankshaft 5. Valve Train Components 6. Lubrication System 7. Cooling System 8. Electrical System 9. Maintenance Schedule 10. Torque Specifications 11. Troubleshooting Guide

Engine Specifications

Complete technical specifications for the 1986 Honda 250 engine.

SpecificationDetails
Engine Type4-stroke, air-cooled, single cylinder
Displacement249cc
Bore x Stroke73.0mm x 59.5mm
Compression Ratio9.3:1
CarburetorKeihin 28mm
Ignition SystemCDI electronic ignition
Starting SystemElectric and kick start
Oil Capacity1.5 liters
Fuel TypeRegular unleaded gasoline
Max Power Output22 hp @ 7,000 rpm

Major Components Overview

Key engine components and their functions.

  1. Cylinder Head: Houses valves and combustion chamber
  2. Cylinder Barrel: Contains piston and combustion area
  3. Crankcase: Encloses crankshaft and connecting rod
  4. Piston Assembly: Transfers combustion energy to crankshaft
  5. Valve Train: Controls intake and exhaust timing
  6. Oil Pump: Circulates lubrication throughout engine

WARNING! Engine components are precision parts; handle with care to avoid damage.

Cylinder Head Assembly

Detailed breakdown of cylinder head components and part numbers.

  1. Remove cylinder head cover: Use 8mm socket, remove bolts in criss-cross pattern
  2. Inspect camshaft: Check for wear on lobes and journals
  3. Valve removal: Use valve spring compressor tool
  4. Cleaning: Remove carbon deposits from combustion chamber
  5. Reassembly: Apply assembly lubricant to moving parts

CAUTION! Always use new gaskets during reassembly to prevent oil leaks.

Piston and Crankshaft

Valve Train Components

Complete valve system parts and specifications.

Intake Valve: Part No. 14711-958-000, Clearance: 0.15mm

Exhaust Valve: Part No. 14721-958-000, Clearance: 0.20mm

Valve Springs: 14751-958-000 (Inner), 14752-958-000 (Outer). Camshaft: 14100-958-000. Rocker Arms: 14411-958-000 (Intake), 14421-958-000 (Exhaust). Valve Guides: 12201-958-000.

Lubrication System

Oil pump and lubrication components.

  1. Oil Pump: Part No. 15100-958-000
  2. Oil Filter: Part No. 15410-958-000
  3. Oil Pressure Switch: Part No. 37530-958-000
  4. Oil Cooler Lines: Check for cracks and leaks
  5. Oil Passage Cleaning: Ensure all passages are clear

Tip: Change oil every 1,000 miles or 6 months for optimal engine life.

Cooling System

Air cooling system components and maintenance.

  1. Cooling Fins: Keep clean and free of debris
  2. Fan Assembly: Part No. 19510-958-000
  3. Thermostat: Part No. 19300-958-000
  4. Temperature Sensor: Part No. 37550-958-000
  5. Cooling Ducts: Ensure proper airflow

WARNING! Never operate engine with blocked cooling fins; risk of overheating.

Electrical System

Ignition and electrical components.

Stator Assembly: Part No. 31100-958-000. CDI Unit: Part No. 30410-958-000. Ignition Coil: Part No. 30510-958-000. Spark Plug: NGK DR8ES-L. Regulator/Rectifier: Part No. 31600-958-000.

Maintenance Schedule

Regular maintenance intervals for optimal performance.

Service ItemIntervalProcedure
Oil Change1,000 milesReplace oil and filter
Valve Clearance2,000 milesAdjust intake and exhaust valves
Spark Plug3,000 milesClean and gap or replace
Air Filter2,500 milesClean or replace element
Carburetor Sync4,000 milesBalance carburetor settings

Torque Specifications

Critical torque values for engine assembly.

CAUTION! Always use torque wrench; do not over-tighten aluminum components.

Troubleshooting Guide

SymptomPossible CauseCorrective Action
Engine won't startFuel, spark, compressionCheck fuel flow, spark plug, compression test
Poor performanceClogged carburetorClean jets and passages; adjust mixture
Excessive oil consumptionWorn rings/valve guidesCompression test; inspect valve seals
OverheatingBlocked cooling finsClean fins; check oil level and quality
Unusual noisesValve clearance/worn bearingsAdjust valves; inspect cam and bearings

Service Support: Contact authorized Honda dealer for genuine parts and technical assistance.

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