How to Change the Coolant on a 2025 Yamaha YZ85 Big Wheel (YZ85LW)
Shop parts for a 2025 Yamaha YZ85LW Dirt Bike.
Maintaining your 2025 Yamaha YZ85LW Big Wheel is essential for peak performance and long engine life–and one of the most critical routine jobs is changing the coolant. The YZ85LW, with its larger wheels and track-ready cooling system, needs clean and fresh coolant for reliable power on every ride.
Why Changing Coolant Matters for the YZ85LW
- Engine cooling: The cool-running two-stroke engine on the YZ85LW is highly dependent on efficient heat transfer. Old coolant can lose efficiency, leading to overheating under race or practice conditions.
- Corrosion prevention: Fresh coolant contains additives that protect the aluminum radiator and engine components from corrosion–critical for long-term durability.
- Model note: The YZ85LW is engineered for aggressive youth racing and frequent revving, so keeping the cooling system in top shape is especially important.
What You Need
- Fresh premixed coolant (engine ice or manufacturer-approved type, ready to install)
- Drain pan
- 10mm socket or wrench
- Clean funnel
- Shop rags
- Flat surface for working
- Protective gloves and eyewear
Coolant Change Steps
- Let the bike cool: Never open the radiator cap on a hot engine–wait until the engine is fully cold to avoid injury and ensure correct coolant levels.
- Stabilize the bike: Position your YZ85LW upright on a bike stand or paddock stand. A slight tilt can cause inaccurate readings or incomplete drainage.
- Remove the radiator cap: Unscrew the radiator cap, located at the top of the left-side radiator. This allows air in and helps draining.
- Locate and loosen the coolant drain bolt: The drain bolt is typically found near the base of the water pump cover (right side of the engine). Place a drain pan underneath and use a 10mm wrench to remove the bolt and let old coolant flow out completely. (There may also be a small copper washer-ensure it does not get lost.)
- Flush if needed: For extra cleanliness, flush the system with distilled water. Pour into the radiator and let it drain fully.
- Reinstall the drain bolt: Once drained, clean the drain bolt threads and reinstall, tightening snugly but not overtight (do not strip the threads). Check washer condition and replace if damaged.
- Add new coolant: Using a clean funnel, slowly pour new coolant into the radiator. Fill until coolant is just below the radiator filler neck. Do not overfill.
- Bleed air bubbles: Gently rock the bike side-to-side to help trapped air escape. Add more coolant if needed.
- Replace the radiator cap: Once the coolant is topped off and air is bled, secure the cap tightly.
- Start and check: Start the engine, run for a few minutes, then shut off and allow to cool. Re-check the coolant level, top off if necessary.
Special Considerations for the 2025 YZ85LW
- Check before every ride: The YZ85LW manual recommends checking coolant level before each use since aggressive riding can consume more fluid.
- Correct coolant level: For proper reading, always check when the engine is cold and the bike is upright–the level should be just at the bottom of the radiator filler neck.
- Big Wheel model dimensions: The LW (Large Wheel) version's added wheel size does not affect the coolant system procedure, but regular inspection is crucial for racers who jump or ride in hot weather.
Final Tips
- Dispose of old coolant safely–never pour it down drains or onto the ground.
- If you spot persistent overheating or coolant loss, check for leaks or consult a MotoSport-certified technician for further diagnosis.
- Your YZ85LW thrives on routine maintenance–staying on top of coolant service will help your bike run cooler and stronger, lap after lap.
Related Shopping Categories
Shop Radiators for a 2025 Yamaha YZ85LW Dirt Bike.
Shop Coolant for a 2025 Yamaha YZ85LW Dirt Bike.
Shop Temperature Sensors for a 2025 Yamaha YZ85LW Dirt Bike.
Shop Tools for a 2025 Yamaha YZ85LW Dirt Bike.
Shop Radiator Hoses for a 2025 Yamaha YZ85LW 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.