How to Change the Coolant in a 1989 Honda CR125

Shop parts for a 1989 Honda CR125 Dirt Bike.

Keeping your 1989 Honda CR125 running cool and reliable requires regular coolant changes. Over time, coolant degrades, risking corrosion, overheating, and poor engine performance. Whether you're prepping for a race or routine maintenance, follow this MotoSport proprietary guide to safely and effectively change the coolant in your classic CR125.

What You'll Need

  • New coolant (preferably motocross-specific, non-silicate, ethylene glycol-based, or a recommended alternative)
  • Distilled water (if diluting concentrate or flushing)
  • Drain pan
  • Sockets or wrenches (commonly 8mm, 10mm)
  • Flathead screwdriver (for hose clamps)
  • Clean rags
  • Safety gloves and eyewear

Step-by-Step Coolant Change Procedure

  1. Let Your Bike Cool Down. Never open the radiator cap on a hot engine to avoid injury from pressurized steam or hot coolant.
  2. Remove the Seat & Side Panels for easier access to the radiator, if necessary for your workspace preference.
  3. Remove the Radiator Cap by turning it counterclockwise. Loosen it slowly to relieve any residual pressure.
  4. Place a Drain Pan under the water pump or the lowest coolant hose. Most CR125s drain best from the water pump bolt, identifiable by its copper sealing washer.
  5. Remove the Drain Bolt or Loosen the Lower Radiator Hose. Use a socket or wrench to remove the drain bolt from the water pump. If your bolt is stuck, you can alternatively loosen the lower radiator hose clamp and pull the hose off the connection to drain.
  6. Allow Coolant to Drain Fully. To help expel remaining coolant, you can gently tilt the bike side to side. For stubborn coolant, use the kickstarter a few times (ignition off) to help push fluid through the system by moving the impeller.
  7. Inspect Coolant for Contaminants. Look for metal shavings, excessive dirt, or oil in old coolant. These may indicate larger issues, like a water pump seal leak.
  8. Reinstall the Drain Bolt or Lower Radiator Hose using a fresh copper washer if available, and tighten just snug–don't overtighten to avoid damaging threads or the pump body.
  9. Refill the Radiator. Pour in fresh coolant (premixed or as directed by the manufacturer). Fill slowly to allow air to escape. The fill capacity for the CR125 is small, so watch as you pour to avoid overfilling.
  10. Bleed the System of Air:
    • With the cap off, gently rock the bike and squeeze the hoses to help any trapped air escape.
    • Check the coolant level again and top off as needed.
    • Reinstall the radiator cap.
  11. Run the Engine Briefly. Start the bike and let it idle with the radiator cap on. Shut it off after a few minutes, and, once cool, check the level again. Top off if the level dropped as air worked its way out.
  12. Inspect for Leaks. Double-check the water pump, radiator hoses, and drain bolt area. Tighten as needed.

Unique Notes for 1989 Honda CR125 Owners

  • Aluminum Radiators: The 1989 model's radiators are prone to damage from improper coolant. Using plain tap water or the wrong antifreeze can accelerate corrosion. Always use distilled water (never tap) for flushing or dilution and motocross-approved coolant to protect internal surfaces.
  • Older Hose Condition: If hoses show cracks, brittleness, or leaks, replace them during this service. Age-related wear is common for original parts.
  • Sensitive Water Pump Seals: The CR125's magnesium cases and seals are sensitive to chemical breakdown. A quality coolant helps maximize water pump and gasket life.
  • Air Entrapment: This generation is susceptible to trapped air due to narrow radiator passages. Take extra time burping the system as directed above for best reliability.
  • Race Prep Tip: Some organizations require non-glycol coolants. Verify before racing and flush thoroughly if switching types.

Total Time Needed

Expect 30-45 minutes for a thorough coolant service. With practice, future changes will be even faster.

Disposal Reminder

Dispose of old coolant responsibly according to local environmental regulations. Coolant is toxic and should never be poured down drains or onto the ground.

Summary

Changing coolant is essential to keep your 1989 Honda CR125 racing strong. With the right parts and attention, you'll help protect your engine for years of two-stroke fun.

Related Shopping Categories

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Shop Radiator Hoses for a 1989 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.