How to Change the Coolant in a 2014 Yamaha YZ125: MotoSport Guide

Shop parts for a 2014 Yamaha YZ125 Dirt Bike.

Maintaining optimal engine cooling ensures your Yamaha YZ125 two-stroke delivers peak performance – and protects its powerplant from unnecessary wear or damage. Regular coolant replacement removes any contaminants that can cause corrosion, overheating, or diminished efficiency. This guide covers everything you need to know about changing the coolant in your 2014 Yamaha YZ125, plus crucial tips unique to your bike.

What You Need

  • Fresh coolant (use high-quality, dirt bike-approved coolant – avoid automotive coolant containing silicates or phosphates)
  • Drain pan
  • Socket wrench set (10mm common)
  • Flathead screwdriver
  • Funnel
  • Clean rags
  • Distilled water (for system flush, optional)
  • Gloves and protective eyewear

Change Procedure

  1. Ensure the bike is cool.
    The cooling system is under pressure at operating temperature. Never attempt to open the radiator cap when the engine is hot. Wait until the engine is completely cool.
  2. Remove plastics for easy access.
    Take off the radiator shrouds using the socket wrench. This will expose the radiator cap and hoses.
  3. Release radiator pressure.
    Slowly open the radiator cap to relieve any pressure in the system.
  4. Locate and remove the drain bolt.
    The YZ125's coolant drain bolt is found on the lower right side of the engine near the water pump. Place your drain pan directly underneath, then use a socket wrench to remove the bolt. Some models use a copper washer – be sure not to lose it.
  5. Drain the old coolant.
    Allow all coolant to drain from the engine and radiator. For a fuller flush, tilt the bike gently from side to side. If flushing the system, reinstall the drain bolt, fill the radiator with distilled water, run the engine briefly, then repeat the draining process.
  6. Inspect hoses and clamps.
    Check all coolant hoses for cracks or signs of wear, and verify that hose clamps are secure but not over-tightened.
  7. Reinstall the drain bolt.
    Clean and reinstall the drain bolt. If your bike uses a copper washer, inspect or replace as needed to ensure a good seal.
  8. Refill with new coolant.
    Using a funnel, slowly pour fresh coolant into the radiator until it reaches the base of the filler neck. The 2014 YZ125 typically requires just under 1 liter of coolant, but always fill per the sight gauge and owner's service manual.
  9. Bleed the system.
    Start the engine and let it idle with the radiator cap off for a couple of minutes – this helps air bubbles escape. Gently squeeze the radiator hoses to help burp the system. Top off the coolant if the level drops and reinstall the radiator cap.
  10. Check for leaks.
    Let the bike run and come to operating temperature while monitoring for leaks around the drain bolt, hoses, and radiator cap.
  11. Reinstall plastics.
    Once you confirm there are no leaks and the cooling system is properly filled, reinstall the radiator shrouds.
  12. Final inspection.
    After a short test ride, allow the bike to cool fully and recheck the coolant level. Top off if necessary.

2014 Yamaha YZ125 Considerations

  • Lightweight aluminum radiators: YZ125 radiators are efficient but susceptible to damage; carefully inspect for bent fins or leaks during coolant replacement.
  • Proper coolant type: The YZ125’s magnesium and aluminum engine cases require a silica-free, dirt bike-specific coolant to prevent corrosion.
  • No coolant reservoir: The system is filled directly via the radiator; routinely check levels before each ride.
  • Frequent maintenance for racers: If you ride hard or on sandy tracks, consider more frequent coolant changes to mitigate heat buildup and debris contamination.

Summary

Changing the coolant on your 2014 Yamaha YZ125 is straightforward but critical. Fresh, high-quality coolant and routine inspection help protect your two-stroke’s engine and keep you riding trouble-free. Always dispose of old coolant responsibly – never pour it down the drain or onto the ground.

Related Shopping Categories

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Shop Radiator Hoses for a 2014 Yamaha YZ125 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.