How to Change the Coolant in a 2009 Yamaha TTR125L

Shop parts for a 2009 Yamaha TTR125L Dirt Bike.

Maintaining the cooling system on your 2009 Yamaha TTR125L is crucial for performance and longevity. While this durable air-cooled dirt bike doesn’t have a liquid radiator system like big-bore motocross models, some late-year TTR125L variants are equipped with a compact radiator and coolant circuit designed to better manage trail heat and reduce engine wear. Here’s how you change the coolant on this specific model—and a few model-specific things every owner should know.

What You’ll Need

  • Pre-mixed motorcycle coolant (or coolant concentrate plus distilled water–never tap water)
  • Socket set & screwdrivers
  • Drain pan
  • Protective gloves and rags

Preparation

  • Ensure the engine is completely cool before starting. Changing coolant on a hot engine can lead to serious burns and pressure spray when opening caps.
  • Park your TTR125L upright on level ground using the kickstand or a bike stand.
  • Remove any bodywork or panels interfering with access to the radiator cap and drain bolt. Most years require removing the left shroud for full access.

Draining the Old Coolant

  • Place your drain pan beneath the water pump–it’s located at the base of the engine, near where the lower radiator hose attaches.
  • Slowly remove the radiator cap to release any residual pressure. Always use a rag over the cap to catch unexpected splashes.
  • Remove the coolant drain bolt from the water pump–expect a strong initial stream, so keep clear.
  • If your bike is equipped with a coolant reservoir, remove and drain it, too.
  • Allow coolant to fully drain from the system. It’s normal for a small air-cooled engine like the TTR125L to drain quickly.

Flushing the System (Recommended)

  • Pour distilled water into the radiator. Replace the cap loosely and run the engine for about 90 seconds to circulate.
  • Shut off, allow to cool, and repeat the drain process. This step helps remove remaining old coolant and debris.

Refilling with New Coolant

  • Install a fresh sealing washer on the drain bolt and torque the bolt securely. Overtightening can crack the aluminum housing.
  • Slowly pour pre-mixed coolant into the radiator up to the base of the filler neck. Filling slowly helps limit air pockets in the system.
  • If using concentrated coolant, mix exactly 50 percent coolant to 50 percent distilled water before filling.
  • Refill the coolant reservoir to the upper line if your bike has one.

Burp the Cooling System

  • Start the engine with the radiator cap off, and let it idle for a few minutes. Gently rock the bike side to side and blip the throttle to help trapped air escape.
  • If the coolant level drops, top it off. Once no more bubbles appear, reinstall the radiator cap securely.
  • Let the engine run long enough to reach operating temperature, ensuring the thermostat opens and coolant circulates.

Final Checks and Disposal

  • After the engine cools completely, recheck both the radiator and the overflow reservoir level. Top up as needed.
  • Inspect all hoses and the radiator cap for leaks.
  • Properly dispose of old coolant–it’s toxic to humans and animals, and should never be dumped outdoors.

2009 Yamaha TTR125L Model Notes

  • The 2009 TTR125L is primarily air-cooled, but always double-check if your specific sub-model has the optional radiator kit. Some trail and MX-L versions were fitted with auxiliary cooling upgrades.
  • Model year 2009 and later TTR125Ls are known for reliable cylinder head gaskets, but improper coolant maintenance can still cause premature gasket failure.
  • Always use Yamaha-approved coolant or an equivalent that’s safe for aluminum engines and cooling systems to prevent corrosion and gasket damage.

Regular coolant changes protect the engine, maximize trail-life, and keep the 2009 TTR125L’s legendary reliability intact—ensuring every ride is a great one.

Related Shopping Categories

Shop Radiators for a 2009 Yamaha TTR125L Dirt Bike.

Shop Coolant for a 2009 Yamaha TTR125L Dirt Bike.

Shop Temperature Sensors for a 2009 Yamaha TTR125L Dirt Bike.

Shop Tools for a 2009 Yamaha TTR125L Dirt Bike.

Shop Radiator Hoses for a 2009 Yamaha TTR125L 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.