How to Change the Coolant in a 2015 Yamaha YZ85
Shop parts for a 2015 Yamaha YZ85 Dirt Bike.
Routine coolant changes are vital for keeping your 2015 Yamaha YZ85 engine performing at its best, especially given its high-revving, competition-oriented two-stroke powerplant. Here is a unique MotoSport.com guide on how to change the coolant, as well as some essential notes specific to this MMY dirt bike.
What You'll Need
- Fresh coolant (Yamaha recommends ethylene glycol-based coolant, pre-mixed or mixed with distilled water to manufacturer specs)
- Basic hand tools (ratchet, socket or spanner set, screwdriver)
- Drain pan
- Rags or paper towels
- Funnel
- Rubber gloves (for safety)
Changing the Coolant – Step-by-Step Instructions
- Let the bike cool completely. The cooling system is under pressure when hot – removing the radiator cap can be hazardous if the system is not fully cooled.
- Remove the radiator cap. Locate the radiator cap on the left side of the YZ85. Twist it off slowly to release any residual pressure.
- Locate the coolant drain bolt. On the 2015 YZ85, the coolant drain bolt is typically found on the lower side of the water pump cover, left-side engine case. Place your drain pan below it.
- Remove the drain bolt and drain old coolant. Use the correct size socket or wrench to remove the drain bolt. Allow all coolant to fully drain into the pan. For a thorough flush, briefly tilt the bike from side to side.
- Flush (optional but recommended). For best results, flush the system with distilled or filtered water to remove any old coolant residue. Reinstall the drain bolt loosely, fill the radiator with water, then drain again. Repeat until the drained water runs clear.
- Install the drain bolt. Use a new gasket or crush washer if possible for a leak-free seal. Tighten the bolt securely, but do not overtighten.
- Add new coolant. Using a funnel, fill the radiator slowly with the recommended coolant.
- Bleed air from the system. Gently rock the bike side to side and squeeze radiator hoses to release trapped air. Top up the coolant if the level drops. Stop when the coolant reaches the base of the filler neck.
- Replace the radiator cap. Ensure it is seated securely.
- Check for leaks and test. Start the bike and let it idle for several minutes. Check for leaks at the drain bolt and cap. After cooling, recheck the coolant level. Top up if needed.
Yamaha YZ85 (2015): Key Owner Tips
- Drain bolt torque: Always tighten the drain bolt to specification to avoid damage. Refer to your YZ85 service manual for recommended torque.
- Coolant quality: Avoid tap water – use distilled or filtered water when mixing coolant to prevent deposits and corrosion in the small YZ85 cooling passages.
- Check hoses & water pump: YZ85s are built for aggressive riding. Always inspect hoses and the water pump for wear or leaks during maintenance.
- Cooling system capacity: The YZ85 has a relatively small cooling system. Overfilling can cause overflow – it is normal for the initial level to drop after bleeding air from the system.
- Service interval: High-performance dirt bikes like the YZ85 often run hot and are pushed hard. Yamaha recommends checking and replacing coolant yearly or every 20–40 hours of use for optimal performance.
Proper cooling maintenance will keep your YZ85 running fast and reliable, whether you're practicing at the track or racing at full throttle.
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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.