How to Change the Coolant in a 1985 Kawasaki KX500

Shop parts for a 1985 Kawasaki KX500 Dirt Bike.

Maintaining the cooling system on your 1985 Kawasaki KX500 is critical for performance – especially given its legendary 2-stroke power output and unique engine characteristics. Regular coolant change helps keep your engine running at optimal temperature and protects vital components during aggressive riding conditions. Below is MotoSport's exclusive step-by-step guide for changing coolant on your classic KX500.

What Makes the 1985 KX500 Cooling System Unique?

  • The KX500 is air-assisted by high-capacity radiators, but 1985 models can be prone to overheating during extended high-rpm use – proper coolant management is key.
  • Unlike modern closed-systems, the 1985 KX500 uses a simple pressurized loop with a radiator cap and a visible overflow.
  • Always inspect for wear on original hoses and radiator cores, as these parts are decades old. Replacements are readily available.

Supplies Needed

  • Fresh premixed coolant recommended for 2-stroke dirt bikes (ethylene glycol-based, silicate-free).
  • 10mm socket or wrench.
  • Phillips screwdriver.
  • Funnel.
  • Catch basin/pan for old coolant.
  • Shop rags/gloves.

Step-by-Step Coolant Change Procedure

  1. Ensure the engine is completely cool before beginning. Place your KX500 securely on a stand.
  2. Remove the radiator cap. Locate and unscrew the cap atop the left-side radiator. For safe draining, remove any bleeder screw present on the opposite radiator tank – this prevents vacuum lock and allows fluid to flow freely.
  3. Position your catch basin/pan under the radiator drain bolt on the lower corner of the radiator.
  4. Unscrew the drain bolt with a 10mm wrench to allow coolant to flow out. For best results, remove any lower side plastics obstructing access.
  5. Once drained, reinstall the drain bolt and securely tighten.
  6. Using a funnel, slowly fill the radiator with fresh coolant. Pour slowly to prevent air pockets and spills. Fill until coolant just reaches the neck of the filler.
  7. Fill the overflow reservoir if equipped, to the marked FULL level.
  8. With both caps off, briefly start the engine for 30–60 seconds to circulate coolant and purge trapped air. Shut down and refill if needed, keeping an eye for visible air bubbles at the neck.
  9. Replace the bleeder and radiator caps, ensuring a tight seal. Twist the cap as specified until fully engaged.

Expert Tips for the 1985 KX500

  • Inspect the radiator, hoses, and fittings for age-related wear – replacement is recommended every few seasons.
  • Flush out any old coolant buildup or scale before refilling. If switching coolant type, perform a thorough flush with compressed air for best results.
  • Check for leaks after your ride. The KX500 engine produces considerable vibration, which can loosen connections over time.
  • Coolant should be changed annually or after any overheating incident for optimal reliability.

Stay on top of maintenance to maximize the legendary performance of your 1985 KX500. Routine coolant change not only protects your engine but preserves the potent ride that makes this model an icon.

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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.