How to Change the Coolant in a 2012 Kawasaki KLX250S

Shop parts for a 2012 Kawasaki KLX250S Dirt Bike.

Changing the coolant in your 2012 Kawasaki KLX250S is a critical maintenance task that protects your engine and maintains optimal performance. The KLX250S features a liquid-cooled, single-cylinder engine that relies on a clean, properly filled cooling system—neglecting coolant changes can lead to overheating and internal damage.

What You Need

  • Approved motorcycle coolant (silicate-free and safe for aluminum engines; avoid standard automotive coolants)
  • Distilled water (if flushing)
  • Drain pan
  • 10 mm and 8 mm sockets with ratchet
  • Funnel
  • Clean rags
  • Protective gloves

Preparation

  • Allow your bike to cool completely—never open the radiator cap on a hot engine.
  • Position the KLX250S upright on a level surface with the sidestand up or use a bike stand for stability.

Coolant Draining Procedure

  • Remove the right side panel and, if needed, the seat, to access the radiator and overflow reservoir.
  • Place a drain pan beneath the water pump, which is located at the lower left side of the engine.
  • Slowly remove the radiator cap to relieve pressure.
  • Locate the coolant drain bolt on the bottom of the water pump and loosen it using a 10 mm socket. Allow the coolant to drain fully.
  • Disconnect the hose from the overflow reservoir and drain its contents.

Flushing the System (Recommended)

  • Reinstall the drain bolt temporarily.
  • Fill the radiator with distilled water.
  • Run the bike briefly (about 1–2 minutes), then turn it off and let it cool.
  • Drain the system again by removing the drain bolt and the overflow hose. Repeat if the drained water appears dirty.

Refilling with New Coolant

  • Ensure the drain bolt is tight and hoses are reconnected.
  • Using a funnel, slowly fill the radiator with new coolant up to the filler neck.
  • Fill the overflow reservoir to the "Full" line.
  • Reinstall the radiator cap securely.

Bleeding Air from the System

  • Start your KLX250S and let it run for several minutes with the radiator cap off (watch for splashing).
  • Gently rev the engine a few times; this helps purge air.
  • Add more coolant if the level drops. Once stable, turn off the engine and replace the cap.
  • Check the overflow again and top off if required.

Important KLX250S Notes

  • The KLX250S cooling system is compact—avoid overfilling, which can cause overflow and pressure issues.
  • Inspect all hoses and clamps for cracks or leaks while panels are off. Replacement when brittle is recommended.
  • This model has an aluminum radiator and engine components—always use silicate-free coolant to avoid internal corrosion.
  • Regular coolant changes (every 2 years or 12,000 miles) extend the life of your KLX250S and help avoid costly repairs.

With regular coolant changes using the correct fluids, your 2012 KLX250S stays ready for every trail and track. Routine maintenance is the easiest way to protect your engine and ensure years of riding enjoyment.

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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.