How to Change the Coolant in a 2009 Kawasaki KLX250S: Step-by-Step Guide

Shop parts for a 2009 Kawasaki KLX250S Dirt Bike.

Regular maintenance keeps your 2009 Kawasaki KLX250S running at peak performance, and coolant changes are essential to prevent overheating while protecting your engine from corrosion. The KLX250S has a straightforward cooling system–but there are a few unique touches compared to other dual-sports. Follow this MotoSport.com proprietary guide to get the job done safely and efficiently.

What You'll Need

  • High-quality motorcycle coolant (silicate/phosphate-free, premixed for aluminum engines)
  • Ratchet with 8mm and 10mm sockets
  • Phillips screwdriver
  • Drain pan/container
  • Funnel
  • Distilled water for flushing (optional but recommended)
  • Clean shop rags
  • Protective gloves

Preparation

  • Begin with a cool engine—never open a hot radiator cap.
  • Place your KLX250S on level ground and secure it on a stand.
  • Remove the seat and left side panel using the 8mm socket to access the radiator cap and overflow reservoir.

Draining Old Coolant

  • Remove the radiator cap slowly to release any residual pressure.
  • Locate the coolant drain bolt on the water pump cover at the bottom right side of the engine. Place a drain pan underneath.
  • Use a 10mm socket to remove the drain bolt and washers.
  • Allow all coolant to fully drain. For a more complete flush, tilt the bike slightly upright.
  • Empty the overflow reservoir by disconnecting it if necessary.

Flushing the System (Recommended)

  • Reinstall the drain bolt and fill the radiator with distilled water.
  • Start the engine and let it run for 2–3 minutes, then shut it off and repeat the draining process.
  • Repeat until clear water drains out.

Refilling New Coolant

  • With the drain bolt securely in place, use a funnel to add coolant slowly through the radiator neck.
  • Fill the radiator to the bottom of the filler neck.
  • Check and fill the overflow reservoir to the “Full” line.
  • Temporarily reinstall the radiator cap, then lean the bike side to side several times to release trapped air.
  • Remove the cap again to top off if needed.
  • Start the engine and let it run for 2–3 minutes with the cap off to purge air from the system. Top off as necessary and reinstall the cap.

Final Checks

  • Inspect for any leaks at the drain bolt and around the hoses.
  • Reinstall side panel and seat.
  • Go for a short ride, allow the bike to fully cool, then recheck coolant level and overflow reservoir.

Important Notes Specific to the 2009 KLX250S

  • This model has a relatively compact cooling system–take care not to overfill the radiator or reservoir.
  • Kawasaki recommends using a silicate- and borate-free coolant to prevent internal corrosion and ensure water pump seal life.
  • The KLX250S is prone to air bubbles–always lean and burp the system during refills.
  • Periodically inspect hoses and the radiator cap. The small radiator commonly suffers damage from crashes or debris.
  • If the engine overheats or loses coolant rapidly, inspect the water pump and radiator for leaks or failures.

A well-maintained cooling system means more time on the trails and less time in the garage. For all genuine parts, maintenance supplies, and coolant options for your 2009 KLX250S, MotoSport.com has you covered.

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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.