How to Change the Coolant in Your 1999 Honda CR500

Shop parts for a 1999 Honda CR500 Dirt Bike.

Regular cooling system maintenance is essential for the legendary 1999 Honda CR500 – an open-class two-stroke motocross icon known for its raw power and enduring reputation. Flushing and refilling the coolant not only helps prevent overheating, but also maximizes the engine’s longevity and performance. This step-by-step MotoSport-exclusive guide covers everything you need to know to change your CR500’s coolant the right way, along with model-specific tips for CR500 owners.

What You’ll Need

  • Ethylene glycol-based motorcycle coolant (safe for aluminum radiators)
  • Drain pan
  • Socket wrench and 10mm socket (for drain bolt)
  • Flathead screwdriver (for plastics, if needed)
  • Funnel
  • Clean rags
  • New water pump crush washer (recommended, Honda part #90463-ML7-000)

Steps to Change Your Coolant

  1. Let the Engine Cool
    Always begin with a cool bike. Never remove the radiator cap when hot. The pressurized system can cause hot coolant to spray out, posing a burn hazard.
  2. Remove Plastics (If Needed)
    For easier access, remove shrouds or any plastics covering the radiator area.
  3. Open the Radiator Cap
    Open the radiator cap slowly to release pressure, allowing air to enter & fluid to drain freely.
  4. Locate the Water Pump Drain Bolt
    On the right side of the engine (clutch cover area), find the water pump housing and the 10mm drain bolt underneath.
  5. Drain the Coolant
    Position your drain pan under the bolt. Loosen & remove the drain bolt; old coolant will pour out. Remove the radiator cap fully to speed up draining. Let it empty as much as possible.
  6. Inspect and Replace the Crush Washer
    Replace the crush washer on the drain bolt to ensure a perfect seal. This helps prevent future leaks.
  7. Reinstall Drain Bolt
    Reinstall and hand-tighten the drain bolt. Torque securely, but do not overtighten – you’re threading into aluminum.
  8. Refill With New Coolant
    Using a funnel, slowly pour new coolant into the radiator neck. Only use ethylene glycol-based coolant designed for aluminum radiators. Avoid tap water mixing, as minerals can build up in the system – only distilled water is safe if mixing is required.
  9. Burp the System
    With the cap still off, start the bike and let it idle 2-3 minutes. Lightly blip the throttle and gently rock the bike to release trapped air bubbles. Watch the coolant level and top off as needed.
  10. Top Off & Refit the Cap
    Fill coolant up to the bottom of the filler neck. Replace the radiator cap. If your CR500 is fitted with a reservoir tank, fill it to the recommended line.
  11. Check for Leaks & Clean Up
    Inspect all fittings, especially the drain bolt and around the radiator, for leaks as the engine warms. Dispose of old coolant properly; never dump it outdoors.
  12. Reinstall Plastics
    Replace any plastics or guards removed earlier.

CR500-Specific Tips & Notes

  • The CR500’s high-compression two-stroke engine runs hot under heavy loads. Fresh coolant is vital – old fluid loses its anti-corrosion and heat transfer properties quickly.
  • This model features aluminum radiators; only use coolants formulated for compatibility with aluminum to prevent internal corrosion.
  • Always inspect radiator fins for debris (mud or grass) and gently straighten bent fins for optimal cooling efficiency.
  • If your CR500 is still running original hoses or cap, consider replacing them periodically—rubber components degrade with age, risking leaks or failure.

A simple coolant change helps preserve your 1999 Honda CR500’s power and reliability, ensuring many more rides of thrilling, big-bore two-stroke performance. For more parts, upgrades, and maintenance essentials, MotoSport is your source for everything CR500.

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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.