How to Change the Coolant in a 2015 Yamaha TTR125L

Shop parts for a 2015 Yamaha TTR125L Dirt Bike.

Changing the coolant in your 2015 Yamaha TTR125L is a crucial maintenance step for efficient engine cooling, extended engine life, and reliable performance on every ride. While the TTR125L's air-cooled 124cc engine means there is no liquid coolant system like those on many full-size motocross bikes, it still requires proper oil maintenance and periodic checks of the frame-mounted oil cooling system. However, if you have an aftermarket conversion or are referencing a different "coolant" such as engine oil or a mini radiated kit, follow this guide for a thorough, MotoSport-backed approach. For standard models, focus on oil changes – but if a coolant system is present, these steps apply.

Preparation

  • Ensure the bike is completely cool before starting to avoid burns.
  • Set the TTR125L securely on a stand or firm surface for stability.
  • Gather supplies: socket set, gloves, drain pan, fresh coolant (for kits), funnel, rags, and eye protection.

Accessing the Cooling System

  • Remove the right side panel (if equipped) and any covers blocking access to the radiator cap or drain bolt. On oil-cooled conversions, locate the oil cooler lines and fittings.

Draining Old Coolant

  • If your model is liquid-cooled or fitted with a conversion kit, locate the radiator drain bolt at the base of the radiator, or the crankcase drain plug if it's an oil cooler. Position a drain pan beneath.
  • Carefully open the radiator cap or oil filler cap to allow air in – never do this while the bike is hot, as pressure may cause burns.
  • Remove the drain bolt and let all coolant/oil drain completely.
  • If flushing is needed (for neglected systems), fill with a mix of distilled water and a small percentage of vinegar, run the engine briefly (monitor closely), then drain again. Flush once more with pure distilled water before final coolant refill.

Refilling the Cooling System

  • Install a new washer or O-ring on the drain bolt and tighten it securely.
  • Slowly pour the correct type and amount of coolant or oil into the filler neck, using a funnel to prevent spills. For coolant systems, slowly fill to avoid air pockets.
  • Gently squeeze cooling hoses to release trapped air. Rock the bike back and forth if needed to help air bubbles escape.

Bleeding the System – Removing Air

  • Leave the cap off and start the engine for a minute or two, monitoring coolant level as air escapes. Rev the engine lightly to help force bubbles out.
  • Top off fluid as necessary, then install the cap securely.

Final Checks

  • Run the engine to operating temperature, then let it cool completely.
  • Re-check and top off the reservoir to the proper fill line.
  • Inspect for leaks at all connections, drain bolts, and around the cap area.
  • Properly dispose of old coolant – do not pour down drains or onto the ground.

TTR125L Model-Specific Notes

  • Standard TTR125L models are air-cooled and do not have a traditional coolant system. If your bike is stock, focus on regular oil changes and inspecting oil cooler lines if equipped.
  • Custom or racing applications sometimes use mini radiators or auxiliary cooling systems; service these as described above.
  • Always consult your owner's manual for recommended fluids and torque specs unique to the TTR125L.

MotoSport brings you the knowledge and parts selection to keep your TTR125L in peak condition through every trail and challenge.

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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.