How to Change the Coolant in a 2002 Kawasaki KX125 – MotoSport Exclusive Guide
Shop parts for a 2002 Kawasaki KX125 Dirt Bike.
The 2002 Kawasaki KX125 is a championship-winning motocross bike renowned for its responsive powerband and light frame. Keeping its cooling system in peak condition is crucial for maintaining engine performance, so regular coolant changes are a must. Follow our robust, MotoSport-specific process to change the coolant in your KX125 – and keep this iconic two-stroke running cool, lap after lap.
Tools & Supplies Needed
- 8mm or 10mm socket (for water pump drain bolt)
- Catch pan or container
- Phillips screwdriver (for radiator cap housing or bleeder if equipped)
- Rag for cleanup
- Fresh coolant – choose a premium motorcycle coolant compatible with aluminum components
- Compressed air (optional, for advanced flushing)
- Gloves and eye protection
Step-by-Step Instructions
- Cool the bike – Make sure your KX125 is completely cool before you begin. Removing coolant from a warm engine can cause burns and may damage engine components.
- Access the radiator and water pump – Place the bike securely on a stand. Remove the radiator shroud if needed to access the radiator cap easily.
- Open the radiator cap – Slowly twist the cap off to relieve any pressure and allow air in. This speeds up draining.
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Locate and remove the drain bolt – On the KX125, the drain bolt is at the bottom of the water pump cover, near the right engine case. Place your catch pan under the area and use your socket to remove the bolt. Allow the old coolant to drain completely.
Tip: For a faster flow and more thorough job, gently lean the bike side-to-side or remove the lower radiator hoses. - Flush the system (optional but recommended) – Pour a small amount of distilled water through the radiator to flush out any remaining old coolant and debris. For a full flush, remove both radiator hoses and use compressed air to blow out any trapped fluid, as the KX125's small passages can collect sediment over time.
- Reinstall the drain bolt – Clean and tighten the water pump drain bolt securely. Avoid overtightening to prevent stripping.
- Add new coolant – Pour fresh, premixed motorcycle coolant into the radiator. Fill until the coolant level reaches the base of the radiator neck.
- Bleed air from the system – Gently rock the bike or squeeze the lower radiator hose to burp out trapped air. Some KX125 models may have a small bleed screw on the opposite radiator – loosen it briefly until fluid escapes, then retighten.
- Reinstall the radiator cap – Secure the cap and reinstall any shrouds or parts you removed.
- Run and recheck – Start the bike and idle it a few minutes. Shut it off and let it cool. Check the coolant level again and top off as needed.
Important Reminders for KX125 Owners
- The 2002 KX125 uses an aluminum radiator – always use coolant that's safe for aluminum to prevent corrosion.
- Inspect your radiator hoses and water pump gasket for wear or leaks during coolant changes. Replace as needed to avoid overheating.
- Dispose of old coolant responsibly – it's toxic to people and pets.
- Check your service manual for coolant capacity, but generally, the total system holds just under one quart (about 900ml).
Maintaining fresh, high-quality coolant is key to the legendary reliability of your KX125. Following this MotoSport guide will help ensure your bike runs strong on the track or trail, no matter how hard you ride.
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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.