How to Change the Coolant in a 2020 Yamaha YZ125
Shop parts for a 2020 Yamaha YZ125 Dirt Bike.
Regularly changing the coolant in your 2020 Yamaha YZ125 is critical for performance and longevity, especially given the demands of off-road riding. The YZ125's two-stroke, liquid-cooled engine relies on effective heat dispersion, and fresh coolant is key for preventing overheating and corrosion in high-rev conditions. Below, find a step-by-step, MotoSport-exclusive guide tailored to your YZ125.
What Makes the 2020 YZ125 Unique?
The 2020 YZ125 features a lightweight aluminum frame and a proven 125cc 2-stroke engine with a liquid-cooled system, engineered for competitive motocross and aggressive trail use. The cooling system capacity and routing are optimized for maximum airflow and low weight, so periodic fluid change is especially important for maintaining peak power and rider confidence. Yamaha recommends coolant changes every two years, but more frequent maintenance benefits riders who operate in tough conditions or race environments–5.
What You Need
- New coolant (use an aluminum-compatible formula, ideally premixed, or mix distilled water and coolant per label instructions)
- Clean funnel
- Socket set
- Drain pan
- Shop rags
- Gloves and eye protection
Step-by-Step Coolant Change Instructions
- Allow the engine to cool completely. Never open the radiator cap while hot.
- Remove the radiator cap. The cap is on the top side of the left radiator shroud. Use a rag to catch any residual spray.
- Locate the coolant drain bolt. On the YZ125, it is usually at the water pump cover on the right side of the engine. Place the drain pan under the drain bolt to catch old coolant.
- Remove the drain bolt and allow all coolant to drain. Open the radiator cap fully to speed the draining process.
- Optionally, flush the cooling system. Reinstall the drain bolt, fill the radiator temporarily with distilled water, remove the bolt again, and drain. Repeat until the water runs clear.
- Once fully drained, reinstall and torque the drain bolt to factory spec to prevent leaks (do not overtighten).
- Slowly fill the radiator with new coolant using a funnel. Fill to just below the neck at the cap.
- Leave the cap off and lean the bike side to side to help burp air from the system.
- Start the engine and let it idle for about 1–2 minutes with the radiator cap off to purge air bubbles. Watch for coolant movement; top off if needed.
- Once no air bubbles appear, install the radiator cap securely.
- Check for leaks at the drain bolt and radiator cap.
Post-Change Checklist
- Verify the correct coolant level with the bike upright. Top off once the system is fully purged and cooled.
- Dispose of old coolant properlyit is toxic to pets, wildlife, and people.
- Inspect hoses and connections for any signs of wear or leaks.
Noteworthy Tips for YZ125 Owners
- The YZ125's radiator is exposedalways inspect for debris and bent fins that may reduce cooling efficiency.
- If you often ride in muddy or sandy conditions, flushing the coolant system more frequently may reduce buildup.
- Use only aluminum-safe coolant; generic automotive coolants can cause corrosion inside your YZ125's system and void Yamaha's warranty.
- The two-stroke YZ125 relies on precise fuel/coolant balance; overheating can quickly ruin piston and cylinder plating, so always ensure proper coolant levels before hard riding or racing.
By following this MotoSport proprietary guide, you'll keep your 2020 Yamaha YZ125 running strong, lap after lap. Regular coolant changes ensure your engine stays cool under pressure—protecting your power and your investment.
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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.