How to Change the Coolant in a 1998 Honda CR125

Shop parts for a 1998 Honda CR125 Dirt Bike.

Changing the coolant in a 1998 Honda CR125 is an essential maintenance task that keeps your bike performing at its best, especially under the demands of off-road riding. This guide from MotoSport.com is designed specifically for CR125 owners and highlights important model-specific tips you need to know.

What You Need

  • Fresh coolant suitable for off-road motorcycles (silicate-free recommended)
  • Phillips and flathead screwdrivers
  • 10mm socket or wrench
  • Drain pan (capacity of at least 3 liters)
  • Clean funnel
  • Distilled water (optional, for flushing)
  • Shop rags
  • Gloves and eye protection

Step-by-Step Coolant Change Procedure

  • Allow the bike to cool completely.
    The 1998 CR125 is a liquid-cooled 2-stroke, and working on a hot system can cause burns and injuries.
  • Remove necessary plastics for access.
    To reach the radiator cap and water pump drain bolt, remove the side panels and seat if access is restricted. On a dirt bike like the CR125, this is usually straightforward with a few bolts.
  • Position the drain pan.
    Place it under the water pump area on the right side of the engine.
  • Remove the radiator cap.
    This relieves system pressure and ensures coolant flows out freely.
  • Locate and remove the coolant drain bolt.
    The CR125 features a 10mm bolt at the water pump cover specifically designed to drain coolant. Carefully loosen and remove it. Some models may use a copper or aluminum crush washer–replace if worn.
  • Let coolant drain completely.
    Wait until the flow completely stops. Tilt the bike gently side-to-side to ensure a thorough drain from both radiators.
  • (Optional) Flush with distilled water.
    If the existing coolant is old or contaminated, reinstall the drain bolt, pour in distilled water, and run the engine briefly. Then shut off, let cool, and repeat the drain. Do not leave plain water in the system for storage or running.
  • Reinstall drain bolt.
    Tighten the drain bolt securely but avoid over-tightening, especially if using a new crush washer.
  • Fill with new coolant.
    Using a funnel, pour new coolant into the radiator neck. Fill to just below the neck to allow expansion.
  • Bleed air from the system.
    Gently rock the bike side-to-side and up-and-down. With the cap off, start the engine and let it idle for a few minutes. Watch for air bubbles to escape. As the coolant level drops, top off as needed until bubbles stop appearing.
  • Replace the radiator cap.
    Install securely once the system is full with no bubbles.
  • Check system for leaks.
    Inspect the drain bolt, hoses, and radiator for leaks once the bike is warmed up.

Model-Specific Notes for the 1998 Honda CR125

  • Watch for corrosion.
    The CR125’s aluminum cooling system can corrode if mixed coolant types are used. Always flush out any old coolant completely and use a silicate-free blend specifically made for aluminum components.
  • Inspect hoses and o-rings.
    This generation is known for aging rubber hoses and seals around the water pump and radiator connections. Check for swelling or cracks and replace as needed to avoid leaks or overheating.
  • Use correct coolant volume.
    The total system capacity is just under 1 liter. Overfilling may result in overflow when the bike is hot.
  • Periodically replace coolant.
    Dirt racing environments and high-revving nature of the CR125 make annual coolant replacement a good idea–even more often if you ride in muddy or sandy terrain.
  • Track overheat risks.
    If you routinely ride at slow speeds or in extreme conditions, consider upgrades like high-flow water pumps or auxiliary fan kits to prevent overheating.

Final Check

  • Run the engine and ensure there are no leaks.
  • After the first ride, check coolant level again and top off if necessary.

Keeping your 1998 Honda CR125’s cooling system maintained is key to reliable power and longevity on any trail or track.

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Shop Radiator Hoses for a 1998 Honda CR125 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.