How to Change the Coolant in a 2020 Honda CRF150R Big Wheel

Shop parts for a 2020 Honda CRF150R Big Wheel Dirt Bike.

Regularly changing the coolant in your 2020 Honda CRF150R Big Wheel is crucial for engine health and optimal performance, whether you are riding tracks or trails. This guide from MotoSport offers a complete, step-by-step process specific to your CRF150RB – including expert notes on this high-performance mini motocrosser.

Things You Will Need

  • Approved coolant: Use Pro Honda HP Coolant or an equivalent high-quality, silica-free coolant formulated for aluminum engines.
  • Drain pan
  • 8mm or 10mm socket or wrench (for drain bolt, check your model)
  • Phillips screwdriver (for radiator shrouds if needed)
  • Distilled water (for flushing, if desired)
  • Shop rags
  • Funnel
  • Rubber gloves – coolant is toxic

Step 1: Prepare the Bike

  • Ensure the engine is cool to prevent burns — never open the radiator cap on a hot engine.
  • Place the bike upright on a stand.
  • If shrouds obstruct the radiator cap, remove them carefully.

Step 2: Drain the Old Coolant

  • Place the drain pan under the water pump area.
  • Locate the coolant drain bolt — near the water pump on the right side of the engine. Remove the bolt and its copper sealing washer (be careful not to lose it).
  • Slowly open the radiator cap to let air in. This allows coolant to drain quickly and completely.
  • Allow coolant to fully drain. Inspect the old coolant for rust or oil contamination, which can indicate other maintenance needs.

Step 3: Flush (Optional but Recommended)

  • If you've had issues with overheating or old, contaminated coolant, flush the system with distilled water.
  • Replace and tighten the drain bolt momentarily, fill the radiator with distilled water, run the engine for about a minute, then let it cool and repeat the drain process.
  • Ensure all flush water is drained before adding new coolant.

Step 4: Reinstall the Drain Bolt

  • Check the drain bolt and copper washer for wear.
  • Reinstall and tighten, but do not overtighten — you can strip the threads in the engine case. If available, use the correct torque spec for your CRF150RB.

Step 5: Add New Coolant

  • Using a funnel, slowly fill the radiator with recommended coolant until it reaches just below the filler neck.
  • Gently rock the bike side-to-side a few times to help air bubbles escape. Top off to the filler neck as needed.
  • Replace and tighten the radiator cap securely.

Step 6: Bleed Air From the System

  • Start the bike and let it idle for a few minutes with the radiator cap on.
  • Shut off the engine, allow it to cool, and check the coolant level again. Top off if necessary.

Step 7: Final Checks

  • Wipe up any spilled coolant immediately; it is both toxic and slippery.
  • Reinstall any radiator shrouds if removed.
  • Run the engine and look for leaks from the drain bolt or radiator area.
  • Dispose of used coolant responsibly, as it is toxic to animals and the environment.

CRF150RB Owner Tips & Model Notes

  • The 2020 CRF150R Big Wheel uses a high-revving, race-bred engine that runs hot under stress, making clean, fresh coolant especially important.
  • Honda recommends replacing coolant at regular intervals or after any episode of overheating to prevent corrosion and maintain cooling efficiency.
  • Stick to approved, silicate-free coolant to avoid clogging radiator cores or damaging the lightweight aluminum cooling system.
  • The cooling system capacity is 0.80 US qt (0.76 L) – do not overfill beyond the radiator neck.

Proper coolant maintenance ensures your CRF150RB stays ready to race or ride with confidence. If you're prepping for a competition or rugged trail season, make coolant inspections a regular part of your routine maintenance plan.

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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.