How to Change the Coolant in a 2019 Honda CRF125F

Shop parts for a 2019 Honda CRF125F Dirt Bike.

Coolant maintenance is crucial for maximizing performance – and longevity – for your 2019 Honda CRF125F. Regular coolant changes help protect your engine from overheating, freezing, and corrosion. If you ride aggressively or in harsh conditions, consider more frequent coolant service.

What Makes the 2019 CRF125F Unique?

The 2019 CRF125F features Honda's advanced air-cooled, four-stroke engine with a reliable liquid-cooled system to prevent overheating under demanding conditions. Unlike many smaller displacement bikes, the CRF125F's compact radiator and streamlined plastic shrouds mean easy access for routine maintenance. Be mindful that using the correct, silicate-free coolant is essential – generic automotive coolants can cause premature wear or cooling system damage.

What You Need

  • Silicate-free, motorcycle-specific coolant (premixed 50/50 preferred)
  • Phillips and flathead screwdrivers
  • Socket set (8mm, 10mm commonly)
  • Drain pan
  • Funnel
  • Shop towels
  • Replacement radiator cap gasket or crush washer (recommended)
  • Distilled water (optional, for flushing)
  • Gloves – always work on a cooled engine

Step-by-Step: Changing Your 2019 CRF125F Coolant

  1. Preparation
    Make sure the CRF125F is on level ground with a cold engine. Remove the seat and right side plastics to expose the radiator cap and overflow reservoir. Have all tools and supplies within reach.
  2. Drain Old Coolant
    Locate the coolant drain bolt, typically found near the bottom of the water pump cover. Position a drain pan underneath. Loosen the radiator cap to release pressure, then remove the drain bolt and let the coolant flow completely out.
  3. Flush (if needed)
    If the coolant appears dirty or you're changing coolant types, flush the system: replace the drain bolt, fill the radiator with distilled water, run the engine briefly, then shut it down and let it cool. Drain again and repeat as necessary until water runs clear.
  4. Install New Crush Washer
    Inspect the drain bolt and replace the washer or gasket if needed to prevent leaks.
  5. Refill with Fresh Coolant
    Using a funnel, slowly add the new coolant into the radiator. Gently squeeze the radiator hose and rock the bike lightly to burp out air bubbles. Fill until the coolant is level with the bottom of the radiator fill neck.
  6. Bleed Air – Final Top Off
    Reinstall the radiator cap loosely. Start the engine and let it idle for a few minutes with the radiator cap open, allowing trapped air to escape. Watch for coolant levels to drop as bubbles escape—top off as needed. Once bubbling subsides and coolant remains steady, secure the cap.
  7. Check Overflow Reservoir
    Fill the overflow tank to the upper mark. Reinstall any removed plastics and the seat.
  8. Final Check
    Run the bike until fully warm, check for leaks, and recheck all fluid levels when cooled. Dispose of the old coolant at an approved recycling facility.

CRF125F Owner Tips

  • Use only Honda-approved or silicate-free motorcycle coolant to prevent internal corrosion.
  • Never mix coolant types unless flushing the system first.
  • Check coolant levels regularly, especially after hard riding or long storage.
  • Always work with the engine cold to prevent scalding injuries.
  • Inspect coolant hoses and radiator cap annually for wear.

Routine coolant changes keep your 2019 Honda CRF125F running cool—no matter the trail or weather.

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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.