How to Change the Coolant in a 2000 Honda CR125: Step-by-Step Guide

Shop parts for a 2000 Honda CR125 Dirt Bike.

The 2000 Honda CR125 is a race-proven 2-stroke built for light weight and rapid handling, but like any performance dirt bike, it depends on healthy coolant for engine protection. Keeping your cooling system fresh reduces the risk of overheating and protects your cylinder and water pump components. Here is a proprietary MotoSport guide to changing the coolant on your 2000 CR125, including unique model notes every owner should know.

Tools – Supplies Needed

  • New coolant (silicate-free, high-performance motorcycle coolant recommended; use 0.88 liters for a change)
  • Drain pan
  • Socket set (10mm and 12mm recommended)
  • Phillips screwdriver
  • Clean rags
  • Optional: funnel, compressed air, parts brush

Step 1: Prepare the Bike

  • Ensure the engine is completely cool before starting, as coolant is under pressure when hot.
  • Support the bike on a stable stand; remove side panels or the seat if needed for better access to the radiator cap.

Step 2: Remove the Radiator Cap

  • Locate the radiator cap on the left side of the bike.
  • With a rag over the cap to catch any residue, press down and turn counterclockwise to remove. (Never remove when hot.)

Step 3: Drain the Old Coolant

  • Position a drain pan beneath the water pump cover area (right side of the engine).
  • Remove the 10mm coolant drain bolt at the bottom of the water pump cover. (Pro tip: The drain bolt may have a sealing washer – do not lose it or reuse if damaged.)
  • Allow coolant to drain fully into the pan. Lean the bike gently side-to-side to evacuate trapped liquid from both radiators.

Step 4: Flush the System (Optional, Recommended)

  • Add clean, distilled water through the radiator cap to rinse the system; let it drain out the open pump. Repeat until clear water exits. (This step removes old deposits and prevents contamination.)
  • Reinstall the drain bolt (use a new crush washer if needed) and torque to spec.

Step 5: Add New Coolant

  • Using a funnel, pour 0.88 liter of new coolant into the radiator, filling slowly.
  • Tap the radiator and hoses to release air pockets. Fill to the base of the radiator neck but do not overfill.

Step 6: Bleed Air – Install the Cap

  • Leave the radiator cap off and start the engine for about 30–60 seconds. Rev lightly once or twice and turn the bike off.
  • Add coolant if the level drops. Repeat once or twice to ensure all air bubbles are purged.
  • Install the radiator cap. Twist until it seats and clicks twice for full lock.

Step 7: Check for Leaks – Safe to Ride

  • Inspect all joints and the water pump cover for leaks. Wipe away any drips.
  • After a short ride, allow the bike to fully cool and recheck the coolant level by removing the cap. Top off as needed.

What Every 2000 CR125 Owner Should Know

  • Coolant level must be checked before each ride – 2-stroke race engines are sensitive to overheating & seized top ends.
  • The 2000 CR125 uses a magnesium water pump cover – always avoid coolants that contain silicates to protect magnesium from corrosion. This is not typical automotive coolant.
  • If you notice any oil in the coolant or vice versa, your water pump shaft seal may be worn – this is a known maintenance item for CR models. Replace immediately to prevent major engine damage.
  • Inspect your radiator hoses for cracks and swelling regularly – hoses lose elasticity with age and heat.

Final Thoughts

  • Changing your coolant annually extends the life of your 2000 CR125's engine and water pump system.
  • If you've rebuilt the top end, changed the head, or replaced the water pump, always fill with new coolant as part of the job.

Related Shopping Categories

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Shop Radiator Hoses for a 2000 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.