How to Change the Coolant in a 1986 Honda CR80: A MotoSport.com Guide

Shop parts for a 1986 Honda CR80 Dirt Bike.

Maintaining optimal cooling is crucial for the longevity – and performance – of your 1986 Honda CR80. Whether you're prepping for race conditions or routine track days, changing your coolant regularly protects the engine from overheating and internal corrosion. The following proprietary MotoSport step-by-step guide walks you through the coolant replacement process tailored to the CR80's distinct design and needs.

What You Need

  • Factory specification ethylene glycol-based coolant (formulated for aluminum radiators)
  • Drain pan
  • Socket set (including 19mm for drain bolt)
  • New crush washer for the drain bolt (Honda part #90463-ML7-000 or equivalent)
  • Funnel
  • Distilled water (for system flush, optional)
  • Protective gloves & eye protection
  • Rags or shop towels

Drain the Old Coolant

  1. Let your CR80 engine cool entirely before working. Coolant under pressure can cause burns.
  2. Remove the seat and left side shroud (refer to your owner's manual for bolt locations – installation for these parts is straightforward on this model).
  3. Place a drain pan beneath the engine block's coolant drain bolt. The 1986 CR80's drain bolt is located near the engine VIN plate. Loosen and remove the bolt (use a 19mm socket). The coolant will drain rapidly once the bolt is out and the radiator cap is loosened for air relief.
  4. Once draining slows, remove the radiator cap completely and inspect the cap's rubber seal for cracks, as aging components are common on bikes this vintage.
  5. Optionally, flush the system by pouring distilled water through the radiator and then draining. This helps clear old coolant and debris – repeat until clear water drains out.

Replace the Drain Bolt & Washer

  • Install a new crush washer on the drain bolt to ensure a proper seal and prevent leaks. Torque the bolt just snug – do not overtighten, as threads can strip easily on older cases. Wipe away excess fluid from the engine area with a rag.

Refill with Fresh Coolant

  1. Slowly fill the radiator with the recommended coolant up to the filler neck. Gently tap the hoses to release trapped air and promote a complete fill.
  2. Replace and secure the radiator cap.
  3. Start the engine and let it run for several minutes. Keep an eye on the temperature and check for any leaks at the drain bolt or hose joints.
  4. Briefly rev the engine and observe coolant movement inside the radiator (through the cap opening before final closure), confirming circulation. Add more coolant if the level drops after cycling air pockets out, then fully reinstall the radiator cap.
  5. Reinstall the side shroud and seat, making sure all mounting hardware is secure.

Important Notes for the 1986 Honda CR80 Owner

  • Use only an ethylene glycol-based coolant – this is critical for aluminum radiators found in your CR80 and prevents both corrosion and internal buildup.
  • The CR80's cooling system is sensitive to air pockets. Impurities or improper fill technique can lead to overheating – bleed air thoroughly as described above.
  • Inspect hoses for hardened or cracking rubber. Honda CR models from the mid-80s are reaching ages where rubber parts may need periodic replacement.
  • Check the radiator cap's spring tension and seal – an original cap may no longer hold correct pressure, so swap as needed.
  • Change coolant at least every two years, or more often if operating in extreme conditions or storing the bike for extended periods.

Keep your classic CR80 performing at its best – fresh coolant doubles as cheap insurance for your two-stroke's high-revving heart. For genuine parts and more model-specific maintenance tips, trust MotoSport.com to help you own the track and your garage.

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Disclaimer: This guide is provided for general informational purposes only and is not intended to replace your motorcycle's official owner's manual. Always refer to your manufacturer's documentation for model-specific instructions, torque specifications, safety procedures, and maintenance requirements. If you are unsure or inexperienced, consider seeking assistance from a qualified mechanic or technician.