How to Change the Coolant in a 1979 Honda CR250: Step-by-Step Guide

Shop parts for a 1979 Honda CR250 Dirt Bike.

Regular coolant changes are essential for keeping your 1979 Honda CR250 running cool and performing at its best. The two-stroke CR250 from this classic era uses a straightforward liquid-cooled system, but, as with all vintage bikes, careful attention and correct procedure are key to preserving your machine. The following MotoSport guide walks you through the coolant change process and highlights important model-specific considerations for your CR250.

Tools & Supplies You Will Need

  • Phillips screwdriver and socket set (for shrouds and tank, if necessary)
  • Drain pan
  • New quality ethylene glycol-based motorcycle coolant
  • Funnel
  • Shop rags
  • Replacement coolant hose or clamps if hoses show signs of age

Step 1: Prepare the Bike

  • Let your CR250 cool completely before starting. This avoids burns and ensures safe cap removal.
  • For easier access, remove the seat and fuel tank. On many vintage CR250s, this involves removing a few bolts and disconnecting the fuel line at the petcock.

Step 2: Drain the Old Coolant

  • Place a drain pan below the water pump drain bolt (typically located on the lower right side of the engine).
  • Remove the radiator cap slowly to release any pressure, then fully remove it.
  • Use the proper-size wrench to loosen and remove the drain bolt. Allow coolant to flow out completely.
  • If the original bolt uses a sealing washer, inspect and replace if necessary to prevent leaks when reinstalled.

Step 3: Flush the System (Optional, but Recommended)

  • For a thorough flush, temporarily reinstall the drain bolt and pour distilled water into the radiator.
  • Replace the radiator cap and gently rock the bike or briefly start the engine (cap on) to circulate water.
  • Repeat the draining process to remove any remaining debris or scale.

Step 4: Refill with New Coolant

  • Tighten the drain bolt to specification.
  • Slowly pour in fresh, high-quality ethylene glycol motorcycle coolant until it reaches the base of the radiator neck. Avoid overfilling.
  • Check coolant hoses for cracks or swellingreplace if needed for reliability.

Step 5: Bleed Air from the System

  • With the radiator cap off, start the engine and let it idle for a few minutes to help trapped air escape. Top off if the level drops.
  • Once full and stable, reinstall the radiator cap securely, ensuring it clicks into place for a proper seal.

Step 6: Final Checks

  • After your first post-service ride, let the bike cool, then open the radiator cap to check and top off coolant level if necessary.

Model-Specific Tips & Notes for the 1979 Honda CR250

  • Vintage radiators are made from softer metals and can be fragile. Avoid overtightening bolts and caps.
  • Genuine or high-quality aftermarket radiators and hoses are recommended; many OEM hoses can harden with age.
  • The CR250 from 1979 was among the early generation of liquid-cooled two-strokes—monitor for leaks at aging joints, and consider pressure testing if coolant loss is recurring.
  • Always use motorcycle-specific coolant, as automotive types with silicates may damage the water pump seals in vintage models.
  • Dispose of old coolant responsibly, as it is toxic to animals and the environment.

Keeping your 1979 Honda CR250 in top shape with regular coolant changes increases engine longevity and on-track reliability. For quality parts, gaskets, and upgraded hoses, remember to Shop parts for a 1979 Honda CR250 Dirt Bike.

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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.