How to Change the Coolant in a 2019 Kawasaki KX85

Shop parts for a 2019 Kawasaki KX85 Dirt Bike.

Properly maintaining the cooling system on your 2019 Kawasaki KX85 ensures optimum engine performance, improved lifespan, and reliability on the track or trail. This two-stroke mini-motocrosser is revered for its high-revving engine, and its cooling system plays a critical role. If you ride often, Kawasaki recommends changing the coolant about once a year or whenever it becomes discolored. This guide covers the process and important notes specific to this model.

What You Need

  • Chemical-safe drain pan
  • 10mm socket or wrench
  • Phillips screwdriver
  • Metric allen wrenches (if removing radiator shrouds)
  • Fresh engine coolant (do not use plain water or automotive antifreeze for aluminum systems)
  • New crush washer for drain bolt (recommended)
  • Clean rag
  • Safety gloves and eye protection

Preparation

  • Ensure the KX85 engine is completely cool before starting. Never open a hot radiator cap due to risk of burns from steam and pressurized fluid.
  • Position the bike on a level stand for easy access.
  • Remove the radiator shrouds if needed (recommended for clearer access).

Drain Old Coolant

  • Remove the radiator cap by turning it counterclockwisedo this slowly to release any pressure.
  • Place the drain pan under the cylinder coolant drain bolt. (On the KX85, this is typically found on the side of the cylinder.)
  • Loosen and remove the drain bolt with your 10mm socket or wrench. Coolant will begin to flow outdirect it into the pan for proper disposal.
  • For complete draining, loosen the radiator hose clamp at the lowest point and carefully detach the hose, allowing remaining coolant to escape.
  • Optionally, remove the small bleed screw on the top of the opposite radiator to allow quicker, fuller drainage and to help air escape during refill.
  • Inspect the crush washer on the drain bolt. Replace it with a new one if there's any deformity or you want to ensure a leak-free seal.

Flush (Optional but Recommended)

  • For thorough cleaning, flush with distilled water only. Fill, run the engine briefly, then drain again.
  • Do not use hard tap water or chemical flush additives, as these can cause corrosion or damage the KX85's aluminum cooling system.

Refill With Fresh Coolant

  • Reinstall the drain bolt with the new (or undamaged original) crush washer and tighten securelynot overtightened to strip the threads.
  • Reconnect and secure the radiator hose if it was removed.
  • On the KX85, use high-quality motorcycle coolant designed for aluminum engines (silicate-free, pre-mixed for convenience and accuracy).
  • Slowly fill the radiator until coolant reaches the top of the filler neck. Stop periodically to let air bubbles escape.
  • If your model has a bleed screw at the top of the radiator or by the thermostat, open this briefly while filling to release trapped air, then close it immediately after coolant seeps out steadily.
  • Gently squeeze the upper and lower hoses to help purge air pockets from the system.

Bleed and Final Checks

  • With the radiator cap still off, start the engine and let it idle for 20-30 seconds. Watch for coolant level to drop as air escapes.
  • Add coolant as needed to keep the filler neck full, then shut off the engine.
  • Once bubbling subsides and the level stabilizes, install and tighten the radiator cap.
  • If equipped, check and top off the overflow reservoir to the max line.
  • Inspect for any leaks at the drain bolt and hose joints. Tighten as necessary.

Model-Specific Tips and Notes

  • The 2019 Kawasaki KX85 cooling system holds about 0.90L (0.95 US qt) of coolant when fully drained. Do not overfill–excess coolant gets pushed into the overflow tank.
  • This model uses twin radiators. Ensure both radiators are bled and check for trapped air—failure to do so can cause overheating and engine damage.
  • Always use a high-quality, pre-mixed coolant that is safe for magnesium and aluminum engine components. Avoid automotive coolant containing silicates or phosphates.
  • If you notice excessive steam, bubbling, or coolant loss after a ride, recheck radiator and hose connections and inspect the radiator cap for proper sealing.
  • Dispose of old coolant responsibly according to local environmental regulations–it is toxic to pets and wildlife.

Enjoy Your Next Ride

Changing the coolant in your 2019 Kawasaki KX85 is a critical maintenance step for peak performance. Performing this job with the right tools and fluids helps you get the most from your bike and extends engine life for many rides to come.

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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.