How to Change the Coolant in a 2010 Yamaha YZ125
Shop parts for a 2010 Yamaha YZ125 Dirt Bike.
Keeping your 2010 Yamaha YZ125 running cool is crucial for peak performance and long engine life. Changing the coolant is a straightforward maintenance task any YZ125 owner can master with minimal tools. Unlike many street bikes, the YZ125's simple cooling system is easy to drain, flush, and refill, but there are important steps unique to this model that you should follow for best results.
Preparation – What You‘ll Need
- Fresh, motorcycle-specific coolant (ethylene glycol-based, not automotive coolant)
- Distilled water (if using concentrate instead of premixed coolant)
- 10 mm socket & ratchet
- Drain pan
- Rags
- Protective gloves
Step-by-Step Coolant Change Process
- Ensure the engine is cool. Never open the radiator cap on a hot engine as pressurized steam and hot coolant can cause burns.
- Remove the radiator cap. The cap is on the left radiator. Loosen it to allow the system to vent and drain freely.
- Locate the coolant drain bolt. On the YZ125, this is the small bolt at the base of the right side of the cylinder water jacket. Place a drain pan under the engine.
- Remove the drain bolt and drain the coolant. Let the coolant completely drain. If you want a more thorough flush, you can gently rock the bike or disconnect the lower radiator hose temporarily.
- Inspect the drained coolant. Look for oil, rust, or metal fragments. These could indicate other maintenance or inspection is needed.
- Flush (if desired): For best results, slowly pour distilled water into the radiator and allow it to drain to flush out residue. Repeat until water runs clear.
- Reinstall the drain bolt. Clean the threads and replace the sealing washer if worn. Tighten to manufacturer specifications (do not overtighten).
- Refill with coolant. Pour fresh coolant into the radiator up to the filler neck. If using concentrate, always mix with distilled water per label instructions.
- "Burp" the system. Leave the radiator cap off. Tilt the bike side to side gently to release air pockets. Start the engine and let it idle for a few minutes while gently blipping the throttle. Watch for any air bubbles escaping.
- Top off the coolant. Once the air bubbles subside and coolant settles, top off to the filler neck as needed.
- Reinstall the radiator cap. Ensure a snug fit—never force it on crooked.
Important Tips Specific to the YZ125
- The 2010 YZ125 has a compact radiator system, so even small air pockets can affect cooling efficiency. Always thoroughly burp the system.
- Never mix coolant types. Use a coolant recommended for aluminum radiators and avoid any solution containing silicates that can damage seals over time.
- This model lacks a separate coolant overflow reservoir—check levels often after the first ride and top off as needed until coolant level stabilizes.
- If you ride in mud or sand, periodically confirm the radiator fins are clean and undamaged for optimal airflow.
After Servicing
- Run the bike briefly until normal operating temperature, then shut it off and recheck coolant level.
- Dispose of old coolant responsibly. Antifreeze is toxic—never pour it on the ground or down the drain.
- Regular coolant changes (every 1-2 seasons) extend the life of your water pump, seals, and engine.
Conclusion
Changing the coolant on your 2010 Yamaha YZ125 is one of the simplest and most effective ways to protect your investment. Take your time, follow the steps above, and your YZ will stay cool no matter how hard you ride. For all of your OEM and performance needs, MotoSport.com is the premier source for YZ125 maintenance and parts.
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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.