How to Change the Coolant in a 1993 KTM 125EXC

Shop parts for a 1993 KTM 125EXC Dirt Bike.

The KTM 125EXC from 1993 features an open-style radiator and a liquid-cooled two-stroke engine. Routine coolant maintenance is critical to avoid overheating and ensure peak performance, especially for older models like this one. This step-by-step guide is tailored for the 1993 125EXC and highlights specific notes every owner should know.

What You Will Need

  • Fresh coolant suitable for aluminum motorcycle radiators
  • Pans or containers to catch old coolant
  • Socket set and basic hand tools
  • Rags for cleanup
  • Funnel and, if possible, a torque wrench
  • Distilled water for flushing (optional but recommended)

Changing the Coolant: Step-by-Step Instructions

  1. Position the bike: Place the motorcycle upright on a stable surface with the engine off and fully cooled. Remove any plastic guards or covers obstructing the radiator cap. This will give you clear access to the cooling system and keep your workspace clean.
  2. Remove the radiator cap: Carefully twist off the radiator cap. Always do this when the engine is cold–opening a hot radiator can spray pressurized coolant and cause burns.
  3. Locate and remove the drain bolt: Look for the coolant drain bolt on the lower part of the engine or water pump cover. Using a socket wrench, loosen and remove the bolt, making sure a container is in place underneath to catch the old coolant.
  4. Drain old coolant: Allow the coolant to fully drain. Gently rock the bike upright if needed to evacuate all fluid. Check the owner's manual for your specific model, but for this generation of KTM EXC, no additional drain plug should be needed–gravity will do the trick.
  5. Flush system (recommended): If you want a thorough flush, reinstall the drain bolt, fill the radiator with distilled water, and briefly run the engine. Shut off, cool down, and repeat the drain process until the water runs clear. This flushes contaminants and old coolant from passageways.
  6. Inspect hoses and clamps: Now is a great time to inspect radiator hoses and hose clamps for cracking or leaks. Replace worn parts as necessary to prevent future problems.
  7. Reinstall the drain bolt: Once fully drained, securely reinstall the drain bolt. Tighten firmly by hand; if you have a torque wrench, torque to about 10 Nm (always confirm with the owner's manual or service spec for the 1993 model).
  8. Refill with coolant: Pour fresh coolant into the radiator up to the filler neck. Avoid mixing different coolant types. If the system requires a premixed 50/50 ratio coolant, make sure the mixture is correct for optimal freezing and boiling protection.
  9. Bleed trapped air: Carefully lean the bike from side to side, then open any bleed screw at the top of the cylinder head (if equipped) to let air escape. Some 1993 125EXC models rely solely on careful filling and rocking the bike to release air bubbles.
  10. Top off and recap: Top off the coolant as needed. Reinstall the radiator cap securely.
  11. Check for leaks and test ride: Start the engine and let it idle until warm. Check for leaks, monitor the coolant level, and add more if the level drops after cycling. Your KTM is now ready for the next ride.

Owner Notes for 1993 KTM 125EXC

  • The 1993 KTM 125EXC does not feature a modern expansion (overflow) tank, so the coolant level must be checked directly in the radiator when cold.
  • Use only aluminum-safe, non-silicate, motocross-specific coolant to prevent corrosion and water pump wear.
  • Periodically inspect radiator fins for mud buildup to maintain optimal airflow–the open fin design of this year is prone to clogging after muddy rides.
  • Given the age, check original radiator caps (0.9 bar pressure rating stock) for deterioration. Replacements are available and can help prevent coolant loss at temperature spikes.
  • Service interval: Change coolant at least once a year or every 40–50 hours of ride time for best protection.

Stay on top of cooling system maintenance and your 1993 KTM 125EXC will keep running strong for seasons to come.

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Shop Radiator Hoses for a 1993 KTM 125EXC Dirt Bike.

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.