How to Change the Coolant on a 2020 Yamaha YZ125X: A MotoSport Exclusive Guide
Shop parts for a 2020 Yamaha YZ125X Dirt Bike.
Changing coolant is a must for prolonging engine life and maintaining peak performance–especially for a high-revving, liquid-cooled two-stroke like the 2020 Yamaha YZ125X. This step-by-step MotoSport guide covers everything a YZ125X owner needs to know, from tools to details unique to this bike.
What Makes the YZ125X Coolant Change Unique?
- Engine design: The YZ125X shares its motor with the legendary YZ125 motocrosser, but with tweaks for woods riding and enduro.
The engine is a single-cylinder, liquid-cooled 2-stroke, and relies heavily on proper cooling for reliability and power delivery.
Always use coolants safe for aluminum engine components. - Rugged use: Hard off-road riding increases the importance of frequent coolant checks since debris and low-speed use can make it run hotter than MX bikes.
- Routine interval: Yamaha recommends changing coolant at least every two years or more often for severe use, including racing or sustained high-temperature operation.
What You Need
- New coolant (look for aluminum-safe premixed, or mix with distilled water per label)
- Socket wrench set
- Phillips screwdriver
- Shop rags
- Drain pan
- Funnel
- Gloves and eye protection
Step-by-Step: Changing the Coolant on Your YZ125X
- Let the engine cool: Never attempt this procedure with a hot engine or radiator. Wait until completely cool.
- Remove side panel (if necessary): For better access, you may want to remove the side panel covering part of the radiator. Use your screwdriver to remove bolts and set the panel aside.
- Position the bike: Place your YZ125X upright on a stand and ensure it is stable. Put the drain pan under the right crankcase area.
- Remove the radiator cap: Slowly unscrew the radiator cap to release pressure and allow the system to drain freely–do this only when the engine is cold.*
- Locate and remove the coolant drain bolt: The coolant drain bolt is typically located at the bottom of the water pump cover (right side of the engine). Use a socket to remove this bolt. Allow all coolant to drain out completely into your pan.
- Flush (optional but recommended): If the old coolant looks dirty or contaminated, flush the system with distilled water by reinstalling the drain bolt, filling the radiator with water, running the engine briefly with the cap off (never rev hard.), then draining again.
- Reinstall drain bolt: Replace the drain bolt and torque it to manufacturer specs. Inspect and replace the crush washer if worn.
- Add new coolant: Using a funnel, add fresh coolant until you see liquid near the filler neck. The recommended coolant capacity is about 1.08 L (1.14 US qt). Fill slowly to avoid air bubbles.
- Bleed air from the system: Gently rock the bike and squeeze hoses to help release trapped air. Top off as needed.
- Reinstall the radiator cap and side panel: Securely tighten the cap and reinstall any panels removed earlier.
- Start and recheck: Let the bike idle until warm, then shut off and allow to cool. Recheck the coolant level at the radiator, topping off if needed. Inspect thoroughly for leaks at the drain bolt and hoses.
Pro Tips for Your YZ125X
- Inspect the radiator and hoses for cracks, bulges, or leaks during every coolant change. Off-road impacts can cause hidden damage.
- Use only premix coolant approved for use in motorcycle aluminum systems for optimal protection against corrosion and boiling.
- Riding in extreme conditions? Consider checking and changing coolant more frequently, as woods and enduro use create extra thermal stress.
- If you notice persistent overheating, inspect your radiator fins for clogs or bends, and check the cap for proper spring tension–both can affect cooling efficiency.
Final Thoughts
Regular coolant maintenance helps your YZ125X perform at its best on the trail, protecting your engine and giving you the confidence to push hard all season. Shop for parts, service kits, and the right coolant at MotoSport–your source for everything YZ.
<.-- *Always confirm specific bolt locations and torque values with your official Yamaha Service Manual for the 2020 YZ125X for maximum accuracy. -->Related Shopping Categories
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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.