How to Change the Coolant in a 1990 Honda CR500: Step-by-Step Guide

Shop parts for a 1990 Honda CR500 Dirt Bike.

Keeping the cooling system healthy on your 1990 Honda CR500 isn’t just basic maintenance—it’s essential for peak performance, heat management, and engine longevity. Dirt, air, and old coolant can cause overheating or corrosion, especially in a powerful two-stroke like this legendary open-class machine. Here’s how to do it right, along with details specific to the 1990 CR500 you should know before grabbing your wrenches.

Tools & Supplies You’ll Need

  • Metric socket set and wrenches
  • Drain pan
  • Soft bristle brush or rag
  • New coolant (choose ethylene glycol based coolant safe for aluminum radiators)
  • Funnel
  • Distilled water (optional, if flushing)
  • Replacement water pump crush washer (recommended for leak prevention)
  • Protective gloves & goggles

Steps to Change the Coolant

  1. Let the Engine Cool
    Never open the radiator cap while hot—the 1990 CR500’s cooling system is pressurized and you risk burns.
  2. Remove the Seat & Shrouds
    Use your metric wrench to access the top of the radiators and filler neck.
  3. Drain the Old Coolant
    Place your drain pan under the water pump (right side, lower engine). Remove the water pump drain bolt. It’s common on most Hondas for the coolant to drain from here.
    Remove the radiator cap to speed up draining.
    For a more thorough drain, gently lean the bike from side to side.
    Replace the water pump crush washer for a proper seal when reinstalling the bolt and torque it to specification.
  4. Flush the System (Optional but Recommended)
    Pour distilled water through the radiator filler neck. Let it drain out the water pump until the flow runs clean. Flushing helps clear out old coolant residue and debris that can plague the CR500’s cooling jackets.
  5. Reinstall Drain Bolt
    Use a new crush washer and hand-tighten, then torque per the service manual (about 10 foot-pounds for most models).
  6. Add New Coolant
    Using a funnel, slowly pour fresh coolant into the filler neck until full. Use an ethylene glycol based coolant–it’s the only coolant safe for the CR500’s aluminum radiators and magnesium cases.
    Tip: Fill right to the bottom of the filler neck.
  7. Bleed Air from the System
    Slowly rock the bike side to side or gently squeeze radiator hoses to help trapped air escape.
    Top off coolant if needed.
  8. Run the Engine
    Start the bike and let it idle until warm (with cap off). Watch for air bubbles; add coolant as needed.
    Once warm, shut off engine, let it cool, and recheck the level. Add coolant if it has dropped.
  9. Reinstall Radiator Cap
    Ensure secure fit. Overfilling can cause overflow—fill to the base of the neck only.
  10. Inspect for Leaks and Clean Up
    Check around the drain bolt and radiator seams for leaks. Dispose of old coolant responsibly.

Things to Know about the 1990 Honda CR500

  • This bike’s engine runs hot—proper coolant levels are crucial, especially on long sand tracks or hot days.
  • The 1990 CR500 uses aluminum radiators–never use plain water or incompatible automotive coolant.
  • The crush washer under the water pump drain bolt is prone to flattening or cracking. Replace each time for a leak-free seal.
  • Due to the harsh two-stroke power delivery, pay attention to radiator fins for mud, bent fins, or other blockages that can affect cooling.

When to Change Coolant

  • Every 1–2 years, or whenever coolant looks dirty, rusty, or has been exposed to freezing conditions.
  • Always change coolant after any major engine work or overheating event.

Final Pro Tips

  • Always check coolant level before each ride for safe operation.
  • Keep your CR500 parked upright for level checks; a slight lean can hide a dangerously low coolant condition.
  • Use only recommended coolants to avoid magnesium and aluminum corrosion, a known issue on vintage two-strokes.

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Shop Radiator Hoses for a 1990 Honda CR500 Dirt Bike.

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.