How to Change the Coolant in a 1989 Kawasaki KX80 Big Wheel

Shop parts for a 1989 Kawasaki KX80 Big Wheel Dirt Bike.

Maintaining the cooling system is critical for the longevity and performance of your 1989 Kawasaki KX80 Big Wheel. Due to its high-revving two-stroke engine and compact radiators, fresh coolant not only ensures reliable riding but also protects the system from corrosion and overheating. Here is MotoSport's proprietary step-by-step guide to changing the coolant on this classic mini motocross machine.

Essential Tools & Materials

  • Ready-mixed motorcycle coolant or concentrate (mixed with distilled water)
  • Socket set or wrench
  • Drain pan
  • Funnel
  • New sealing washer for drain bolt (recommended)
  • Gloves & rags

Preparation

  • Allow the engine to cool completely before starting the procedure.
  • Place the bike on a stand or securely on level ground.
  • Remove the seat and side panels if they block access to the radiator cap or overflow tank.

1. Draining the Old Coolant

  • Locate the radiator cap on the left side of the bike and the drain bolt at the water pump (bottom left engine case).
  • Remove the radiator cap to relieve pressure.
  • Position a drain pan beneath the water pump. Remove the drain bolt and let the coolant fully drain.
  • If equipped, disconnect the overflow hose and drain the expansion tank as well. This is especially important on older bikes since residue can accumulate in expansion tanks.

2. Inspect & Clean

  • Check all hoses and clamps for cracks, stiffness, or leaks. Replace any brittle hoses–these can become a common failure point on older KX80 models due to age.
  • Inspect the radiator for bent fins or damage. Straighten with a small flathead screwdriver if necessary.
  • If the expansion tank is dirty, flush with clean water and gently scrub to remove any deposit buildup.

3. Refitting the Drain Bolt

  • Install a new sealing washer on the drain bolt for optimal sealing and thread it back into the water pump.
  • Tighten the bolt securely, but be careful not to overtighten–the cases are aluminum and can strip easily.

4. Filling with Fresh Coolant

  • Slowly pour the new coolant into the radiator until the fluid is just below the filler neck. Use a funnel to minimize spillage and avoid introducing air bubbles.
  • Top up the overflow tank as well, filling to the indicated upper mark.

5. Bleeding Air from the System

  • With the radiator cap still off, start the engine and let it idle for 2–3 minutes. Gently blip the throttle several times to encourage trapped air to escape–this is especially important on two-strokes where air pockets can cause rapid overheating.
  • Turn off the engine and allow a minute for the coolant to settle.
  • Check the coolant level. Top off if necessary so that the radiator is full up to the neck, and the expansion tank is at the upper mark.

6. Sealing & Final Checks

  • Reinstall the radiator cap securely.
  • Wipe away any spilled coolant, reinstall body panels or seat if removed.
  • Dispose of old coolant at an appropriate recycling facility.

Special Notes for the 1989 KX80 Big Wheel Owner

  • The KX80BW is known for high-revving performance, making effective cooling crucial–never run the bike with low coolant or air in the system.
  • Due to age, watch for corrosion or pitting on the water pump cover and cylinder. Even minor cracks or worn gaskets can cause coolant leakage into the engine, risking performance loss or engine damage. If you observe milky oil or unexplained coolant loss, inspect these areas closely.
  • Factory spec recommends regular inspection of the cooling system hardware and immediate replacement of any worn parts to avoid unexpected failures during rides or races.

Maintenance Tips

  • Monitor coolant level in the first few rides after the change–air pockets may settle out with use and require a minor top-off.
  • Change coolant every 1–2 years or per your riding environment; more frequent changes are needed if regularly riding in muddy or sandy conditions.

Related Shopping Categories

Shop Radiators for a 1989 Kawasaki KX80 Big Wheel Dirt Bike.

Shop Coolant for a 1989 Kawasaki KX80 Big Wheel Dirt Bike.

Shop Temperature Sensors for a 1989 Kawasaki KX80 Big Wheel Dirt Bike.

Shop Tools for a 1989 Kawasaki KX80 Big Wheel Dirt Bike.

Shop Radiator Hoses for a 1989 Kawasaki KX80 Big Wheel 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.