How to Change the Coolant in a 2021 Honda CRF450RL

Shop parts for a 2021 Honda CRF450RL Dirt Bike.

Keeping your 2021 Honda CRF450RL in peak condition means staying ahead on maintenance, and one of the most crucial but overlooked tasks is changing the coolant. The CRF450RL's high-performance liquid-cooled engine demands clean, high-quality coolant to prevent overheating and corrosion, especially if you ride hard and often. Here's a MotoSport-exclusive guide that will walk you through changing the coolant with tips unique to your model.

Why Change the Coolant?

Coolant breaks down over time, loses effectiveness, and contaminates with engine debris. Honda recommends replacing the coolant every two years or 24,000 miles, whichever comes first. The CRF450RL's dual-sport design means you may spend long hours at a wide range of engine speeds–fresh coolant is critical in both hot trail conditions and long road stretches.

Tools and Supplies Needed

  • Silicate-free, motorcycle-specific coolant (never use car coolant)
  • 8mm and 10mm sockets
  • Ratchet
  • Phillips screwdriver
  • New brass or aluminum crush washer for the drain bolt
  • Drain pan
  • Funnel
  • Clean rags or paper towels
  • Torque wrench (recommended)
  • Safety gloves

Step-by-Step Instructions

  1. Prepare the Bike:
    • Make sure your bike is completely cool before starting. Hot coolant can burn and is under pressure.
  2. Remove Engine Guard:
    • The 2021 CRF450RL is equipped with a skid plate (engine guard) that covers the water pump drain bolt. Remove the fasteners (8mm or 10mm bolts) and take off the skid plate for easy access to the drain bolt at the bottom of the right-side engine cover. Note bolt length for proper reassembly–long and short bolts have specific locations.
  3. Remove Plastics (if necessary):
    • Some radiator shrouds or side panels may partially block the radiator cap. Remove with a 5mm or 8mm tool as needed.
  4. Drain the Old Coolant:
    • Place a drain pan beneath the water pump on the lower right side.
    • Remove the radiator cap to release system pressure. This helps coolant drain freely.
    • Remove the water pump drain bolt and crush washer. Let all old coolant drain. Inspect the old coolant–milky or rust-colored fluid suggests other engine concerns.
    • Dispose of coolant responsibly–do not pour down the drain or on the ground.
  5. Replace the Crush Washer:
    • The factory drain bolt uses a single-use crush washer that should be replaced at each coolant service. This ensures a proper seal and prevents leaks.
    • Reinstall the drain bolt and torque to spec: approximately 10 N·m (7 lb·ft).
  6. Fill with New Coolant:
    • Using a funnel, pour fresh silicate-free coolant into the radiator. Fill just below the filler neck to allow for expansion.
    • Do not overfill. Clean any spills immediately to protect plastics and paint.
  7. Bleed and Check for Air:
    • Start the bike and let it idle with the radiator cap off. Some bubbles may emerge as the thermostat opens and trapped air escapes. Top off coolant as the level drops.
    • Once bubbling ceases and coolant level stabilizes, shut the engine off and allow it to cool. Reinstall the radiator cap firmly.
  8. Reinstall Plastics and Guard:
    • Replace the engine guard/skid plate, torque all fasteners to spec.
    • Reinstall any side panels or shrouds as removed.
  9. Test Ride and Recheck:
    • Start the engine, let it warm up, then check for leaks around the water pump, drain bolt, and radiator cap.
    • After a brief test ride, let the engine cool and double check the coolant level in the radiator and overflow bottle (if equipped). Top off if needed.

CRF450RL Model Notes & Tips

  • The 2021 CRF450RL uses a high-compression Unicam engine derived from Honda's racing lineage. Keeping the cooling system in top shape is critical for longevity, especially under hard enduro or long dual-sport rides.
  • Never mix different coolant types. Always use pre-mixed motorcycle coolant with silicate-free corrosion inhibitors to protect the alloy components.
  • Check and replace radiator hoses if they're brittle or swollen; stock hoses can degrade over time under high-heat conditions.
  • It's good practice to inspect the radiator cap seal during service–a worn cap may not hold pressure and can lead to overheating.
  • If you ride in extremely muddy or dusty areas, periodically clean radiator fins to prevent overheating.

Routine cooling system maintenance is the easiest way to safeguard your CRF450RL's engine for years of adventure. Stay ahead of the game with a fresh coolant change, and enjoy reliable power wherever you ride.

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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.