How to Change the Coolant in a 1987 Kawasaki KX125

Shop parts for a 1987 Kawasaki KX125 Dirt Bike.

Proper coolant maintenance is critical to keeping your 1987 Kawasaki KX125 running cool, especially under the rigorous demands of dirt bike riding. This two-stroke machineknown for its high-revving performance and lightweight chassisdemands a clean, correctly mixed coolant system to prevent overheating and prolong engine life. Follow this guide for a robust, model-specific process.

What You Need

  • 50/50 mix of soft water – permanent-type coolant (green in color, specifically for aluminum engines and radiators)
  • Catch pan for old coolant
  • Socket/ratchet set (usually 8mm/10mm)
  • New radiator cap (optional but recommended for older bikes)

Important Notes for the 1987 KX125

  • Total coolant capacity: 0.96L
  • The KX125 uses an aluminum engine and radiatornever use silicate-based or automotive coolant that may harm internal surfaces
  • The radiator cap pressure spec is 95–125 kPa (14–18 psi)

Coolant Change Steps

  1. Cool Down: Let the engine cool fully before removing the radiator cap to avoid burns or injury. Do not attempt to change coolant while hot.
  2. Remove the Radiator Cap: With the engine cool, place your catch pan under the bike and carefully remove the radiator cap.
  3. Locate and Remove the Drain Bolt: On the 1987 KX125, the coolant drain bolt is typically located at the water pump cover. Use your socket set to carefully loosen and remove it. Allow all coolant to fully drain into your catch pan.
  4. Flush If Necessary: If the drained coolant is dirty or has debris, consider flushing the system with distilled water. Reinstall the drain bolt securely after draining.
  5. Refill Coolant: Slowly fill the radiator with your 50/50 coolant mix, up to the base of the filler neck. Do not overfill. Take care to pour slowly to prevent introducing air bubbles into the system.
  6. Bleed Air from System: Briefly lean the bike side to side and gently squeeze radiator hoses to help release trapped air. Top off coolant as needed.
  7. Run and Heat Cycle: Leave the cap off, start the bike, and let it idle until the engine is warm. Watch for the coolant to circulate. If coolant drops in level, top off to the appropriate level.
  8. Final Check and Cap: Let the engine cool completely. Re-check coolant level. Add if required, then securely replace the radiator cap.

Maintenance Tips for the 1987 KX125

  • Always check coolant level before each ride – this model is sensitive to overheating
  • Replace the radiator cap if it shows wear, as a weak cap can cause premature boiling
  • Inspect the radiator and hoses for leaks, especially at the age of this vintage KX
  • Stick strictly to the recommended coolant type & mix ratio

Routine coolant changes not only protect your 1987 KX125 engine but help maintain top power output during demanding rides. Keep your cooling system in peak condition for lasting performance out on the track or trail.

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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.