How to Change the Coolant in a 2007 Honda CR85 Big Wheel: MotoSport.com Guide

Shop parts for a 2007 Honda CR85RB Dirt Bike.

The 2007 Honda CR85RB (Big Wheel) is a race-bred, two-stroke mini motocross machine, and keeping the cooling system in top condition is key to performance and longevity. Routine coolant changes prevent overheating, corrosion, and premature engine wear–especially after every season or approximately every 40-50 hours of use, or sooner if you ride in harsh conditions.

Why Coolant Service Matters on the CR85RB

The CR85RB has a high-revving engine and compact radiator system. Because it runs hotter and harder than many trail models, fresh, high-quality coolant is especially important. Always use Pro Honda HP coolant or an equivalent performance-grade ethylene glycol coolant designed for aluminum engines. Never use plain water, as it provides inadequate freeze, boil-over, and corrosion protection1.

Essential Tools & Supplies

  • Coolant catch pan
  • 8mm or 10mm socket/wrench (for drain bolt)
  • Needle-nose pliers (for hose pinch)
  • Shop towels/rags
  • Funnel
  • New crush washer for drain bolt, if needed
  • Pro Honda HP coolant or equivalent
  • Safety glasses & gloves

Step-by-Step Coolant Change Procedure

  1. Prep the Bike
    Ensure the engine is completely cool. Move your CR85RB to a level work area with good ventilation.
  2. Remove the Radiator Cap
    Loosen and remove the radiator cap slowly to release any residual pressure.
  3. Locate the Water Pump Drain Bolt
    On the CR85RB, the coolant drain bolt is found low on the right side, at the water pump cover. It typically has a copper or aluminum crush washer behind it1.
  4. Drain the Old Coolant
    Position your catch pan under the drain. Remove the bolt and washer. Old coolant will flow out quickly.
    Tip: Carefully lean the bike from side to side to help fully evacuate the system.
  5. Inspect and Replace Washer
    Check the drain bolt's crush washer for wear. Replace with new if flattened or damaged–this prevents leaks.
  6. Reinstall the Drain Bolt
    Once fully drained, reinstall the drain bolt (& new washer), tightening securely but not overtightening.
  7. Flush if Needed
    For extra thoroughness, flush the system by refilling with distilled water, running briefly, then repeating the drain. Do this until water drains clear if old coolant was very dirty.
  8. Add New Coolant
    Slowly pour fresh coolant into the radiator. Fill to the top of the filler neck.
  9. Bleed Air from the System
    With the radiator cap off, start the engine and let it idle. As air bubbles escape, the coolant level may drop–top it up as needed. Once the system is bubble-free and to the proper level, install the radiator cap.
  10. Check for Leaks
    Inspect all hoses, the radiator, and the drain bolt for leaks. Wipe up any spills.

Special Tips for 2007 CR85RB Owners

  • This model uses specific radiator hoses and narrow passages–always double-check for clogs if your old coolant was rusty or contaminated.
  • Race use leads to higher engine temps–consider upgrading to a premium, high-boiling-point coolant for maximum protection.
  • Inspect for cracked hoses and warped radiator fins during coolant changes. Replace as needed to prevent overheating.
  • Always recycle old coolant properly–it is toxic and should never be poured down drains or onto the ground.
  • Check the coolant level regularly, especially after your first ride post-change, as residual air can work its way out and drop the level slightly.

Conclusion

Coolant replacement is quick, low-cost insurance against severe engine damage. With a simple set of tools, high-quality coolant, and some basic care, your 2007 Honda CR85RB Big Wheel will stay fast and reliable at the track or on the trail.

Related Shopping Categories

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Shop Temperature Sensors for a 2007 Honda CR85RB Dirt Bike.

Shop Tools for a 2007 Honda CR85RB Dirt Bike.

Shop Radiator Hoses for a 2007 Honda CR85RB 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.