How to Change the Coolant in a 1986 Kawasaki KX125
Shop parts for a 1986 Kawasaki KX125 Dirt Bike.
Maintaining the cooling system is crucial for the performance and longevity of your 1986 Kawasaki KX125. Regular coolant changes keep your engine running smoothly, prevent overheating, and protect components from corrosion and scale buildup. Here is MotoSport.com's proprietary guide for changing the coolant in your classic KX125.
Tools & Supplies Needed
- Phillips screwdriver
- 10mm socket or wrench
- Drain pan or clean container
- New coolant (compatible with KX125)
- Compressed air (optional for thorough system flush)
- Rags for cleanup
Step-by-Step Coolant Change Instructions
-
Prepare the Bike
Place your KX125 on a stable stand. Make sure the engine is cool before you begin. -
Access the Radiator
Remove the radiator cap to release any pressure. The KX125 is equipped with a coolant bleeder screw on the opposite side of the radiator—use your Phillips screwdriver to loosen it for easier draining and to prevent vacuum lock. -
Locate and Remove the Drain Bolt
Find the drain bolt at the bottom of the water pump housing (usually on the right side of the engine). Place your drain pan underneath, then use your 10mm socket to remove the bolt. Coolant will start to flow out–opening the radiator cap ensures a steady flow. -
Flush the Cooling System (Optional)
If switching to a different coolant type or for a thorough clean, remove hoses from the radiator and use compressed air to blow out residual coolant. Avoid using tap water if you're changing from water-based to non-water coolant mixtures. -
Inspect Components
Check the radiator cap for damage or bent edges. Confirm the bleeder screw threads are intact. Clean up any spilled coolant with rags. -
Refill with New Coolant
Reinstall the drain bolt and tighten securely by hand to avoid cross-threading. Pour the new coolant slowly into the radiator. Fill until liquid appears at the bleeder screw opening. Tighten the bleeder screw, then finish topping off the radiator until full. -
Final Checks
Start your engine and let it idle briefly. Check for leaks around the drain bolt, radiator cap, and hoses. Once the bike cools, recheck coolant level and top off if needed.
KX125 Specific Notes & Tips
- The 1986 KX125 utilizes a simple single-radiator design. The cooling capacity is adequate for high-rev riding, but always ensure there is no debris blocking airflow through the fins, especially after muddy rides.
- The water pump gasket should be inspected whenever you drain the coolant. If you notice signs of leakage or wear, replace the gasket during the service to avoid future problems.
- Always use a high-quality, motorcycle-specific coolant for best results–mixing coolant types can reduce performance or cause chemical incompatibility.
Environmental & Safety Considerations
- Dispose of old coolant safely–never pour it down the drain or onto the ground. Local auto shops or hazardous waste facilities can handle this for you.
- Wear gloves and work in a well-ventilated area to avoid skin or inhalation contact.
By following this guide, you'll keep your 1986 Kawasaki KX125 running cool and strong–ready for every 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.