How to Change the Coolant in a 1980 Honda CR250: A Step-by-Step Guide

Shop parts for a 1980 Honda CR250 Dirt Bike.

The 1980 Honda CR250 remains an iconic motocross machine, known for its lightweight chassis, responsive two-stroke power, and liquid cooling system – a pioneering feature at the time. To ensure optimal performance and protect your engine from overheating or internal corrosion, routine coolant replacement is crucial. Follow this MotoSport-exclusive guide for a safe and thorough coolant change specific to your CR250.

Preparing for Coolant Replacement

  • Let the engine cool completely. Hot coolant can scald—always work with a cold bike.
  • Find a suitable, well-ventilated workspace and use a drain pan to catch old coolant—preventing environmental harm.
  • Gather supplies: fresh, silicate-free antifreeze/coolant (mixed 50-50 with distilled water unless using premix), rags or towels, a funnel, a 10mm socket/wrench, and safety gloves.

Removing the Old Coolant

  • With the bike upright (use a stand if possible), carefully remove the radiator cap. Loosen it to relieve pressure but do not fully remove until pressure is released.
  • Locate the coolant drain bolt—typically a 10mm bolt on the water pump cover near the bottom left of your engine.
  • Place the drain pan under the bolt. Unscrew the drain bolt and allow all coolant to empty. Lean the bike gently side to side to ensure complete drainage.
  • If the coolant appears rusty, milky, or contains debris, flushing the system with distilled water is recommended. Reinstall the drain bolt temporarily, fill the radiator with distilled water, run the engine briefly, shut it off, and drain again. Repeat until only clear water drains.

Refilling with Fresh Coolant

  • Inspect the drain bolt crush washer for wear. Replace if damaged to prevent leaks.
  • Reinstall and securely torque the drain bolt (do not overtighten).
  • Using a funnel, fill the radiator through its cap opening with your coolant mix until fluid reaches just below the neck.
  • With the cap still off, gently rock the bike to dislodge air bubbles. Top up if necessary.
  • Start the engine and let it idle with the cap off for 1–2 minutes. Watch for air bubbles and add coolant as the level drops. Turn off the engine and allow it to cool before installing the radiator cap securely.

Final Checks

  • Visually inspect for any leaks at the drain plug, radiator seams, and hose connections.
  • Check coolant level after the next ride (once the engine has cooled) and top off if needed.
  • Safely dispose of old coolant—never pour it down drains or on the ground.

Model-Specific Tips & Notes for Your 1980 Honda CR250

  • The 1980 CR250 uses a pioneering liquid-cooling system for superior high-RPM durability compared to most other bikes of its era.
  • Always use silicate-free coolant designed for aluminum engines to prevent internal corrosion.
  • Inspect your vintage bike's radiator hoses and clamps for aging or brittleness; replace any compromised parts with correct-fit replacements to maintain reliability.
  • If you perform regular hard riding or racing, check coolant condition mid-season and replace more frequently as needed.

Regular attention to your CR250's cooling system is essential for keeping this legendary two-stroke ripping for years to come.

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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.