How to Change the Coolant in a 2024 Yamaha YZ125X

Shop parts for a 2024 Yamaha YZ125X Dirt Bike.

Regular coolant changes are essential to keep your 2024 Yamaha YZ125X running cool & reliably, especially when tackling demanding trails or race courses. The following guide gives you model-specific steps for replacing your coolant and details unique maintenance notes for this championship-caliber two-stroke dirt bike.

What Makes Coolant Changes Important on the 2024 YZ125X?

This model uses a high-performance, liquid-cooled 125cc two-stroke engine. Frequent coolant maintenance helps prevent overheating, corrosion, and premature wear – extending the life of vital engine components. Always use a high-quality ethylene glycol-based coolant made for aluminum engines and mixed 1:1 with distilled water for best results.

Essential Supplies & Tools

  • New coolant (aluminum-compatible, pre-mixed or mix with distilled water)
  • 10mm socket and ratchet
  • Flathead screwdriver
  • Pliers
  • Drain pan
  • Clean rags
  • Protective gloves and eyewear (coolant can irritate skin and eyes)

Step-by-Step Coolant Change Instructions

  1. Let the engine cool completely.
    Never open the radiator cap when the engine is hot. The system is pressurized and can spray hot coolant – wait at least one hour after riding for safety.
  2. Remove the seat and left side panel.
    This grants easier access to the radiator cap and drain bolt.
  3. Place a drain pan under the water pump area.
  4. Remove the radiator cap.
    Twist off the cap to allow air into the system – this helps coolant drain more completely.
  5. Locate the coolant drain bolt.
    On the YZ125X, it is on the lower right side of the engine case (part of the water pump cover). Use a 10mm socket to carefully loosen and remove the bolt. Also remove the copper crush washer if present.
  6. Let the old coolant drain out fully.
    Tilt the bike slightly (use a stand if available) to ensure all fluid exits both radiators.
  7. Inspect the drained coolant.
    Look for oil contamination or metallic particles, which can indicate engine issues needing further attention.
  8. Reinstall the drain bolt and washer.
    Torque the drain bolt to specification (typically around 7Nm / 5 ft-lb – confirm in your owner’s manual).
  9. Refill the radiators with new coolant.
    Slowly pour in fluid until it reaches just below the base of the fill neck. The standard capacity is approximately 0.90L (0.95 US qt) for the entire system.
  10. Bleed air from the system.
    Loosen the air bleed screw located on the right or left radiator (if equipped), or gently rock the bike back and forth to help trapped air escape. Add coolant as the level drops, then re-tighten the bleed screw.
  11. Reinstall the radiator cap.
    Tighten securely until it clicks or locks in place.
  12. Reinstall the seat and side panel.
  13. Start the engine briefly and inspect for leaks.
    Let it idle for several minutes, then shut off and allow the bike to cool. Recheck the coolant level – top off to the fill neck if needed.

Model-Specific Maintenance Tips for the 2024 Yamaha YZ125X

  • Always use aluminum-compatible coolant.
    The YZ125X features lightweight, aluminum radiators and a magnesium engine case that require high-grade, anti-corrosion coolant to resist electrolysis.
  • Check for muddy or clogged radiators.
    Off-road conditions can pack mud or debris into the radiator fins, cutting cooling efficiency. Rinse thoroughly with low-pressure water after rides.
  • Inspect all hoses and clamps each service interval.
    Replace any cracked, swollen, or weeping hoses immediately.

Dispose of Used Coolant Responsibly

Never pour old coolant down the drain or on the ground. Collect it in a sealed container and drop off at an authorized recycling or hazardous waste facility.

Stay Ahead with MotoSport

With proper maintenance, your YZ125X’s cooling system will keep up with every lap or adventure ride. For OEM and upgrade cooling parts, shop parts for a 2024 Yamaha YZ125X 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.