How to Change the Coolant in a 2018 Sherco 125SE-R

Shop parts for a 2018 Sherco 125SE-R Dirt Bike.

Maintaining the cooling system on your 2018 Sherco 125SE-R is essential for peak performance and engine longevity. Over time, coolant can lose its effectiveness and even damage internal components if not replaced as recommended. Follow this MotoSport guide for a safe and effective coolant change, tailored specifically for the Sherco 125SE-R two-stroke dirt bike.

Tools & Materials Needed

  • Correct type of approved motorcycle coolant (never use plain water or unapproved fluids as these can harm your engine – always follow manufacturer specification)*
  • Phillips screwdriver or specific wrench for bleed/drain screws
  • Clean rags and a catch pan
  • Funnel
  • Gloves and safety glasses

Step-by-Step Coolant Change Procedure

  1. Allow the engine to cool completely. Never remove the radiator cap when the engine is hot; pressurized coolant can cause severe burns.
  2. Remove the seat and fuel tank to access the radiator and associated components, if necessary. This bike's design may require lifting the tank for easier access to the radiator neck and bleed screw*.
  3. Position a drain pan underneath the engine's lowest coolant hose or drain screw.
  4. Loosen and remove the radiator cap.
  5. Locate and remove the coolant drain/bleed screw on the right side of the engine or at the bottom of the radiator. Allow coolant to completely drain.
  6. Inspect coolant for contamination. If you see metal flakes, sludge, or oil, further inspection of the cooling system or motor may be necessary before refilling.
  7. Reinstall the drain/bleed screw securely once drained. Some models require a new crush washer.
  8. Pour fresh coolant into the radiator through the filler neck. Fill slowly, allowing air to escape. If your Sherco has a bleed screw at the top of the radiator/head, open it while filling to vent trapped air.
  9. Check the coolant level, ensuring it's slightly below the filler neck when the radiator is upright.
  10. Replace the radiator cap securely.
  11. Start the engine and let it idle until the thermostat opens (the radiators warm up evenly). Watch for leaks and monitor the overflow for bubbles that indicate trapped air.
  12. Turn off the engine, let it cool, then recheck coolant level. Top off as necessary.

2018 Sherco 125SE-R Model-Specific Notes

  • Only use coolants approved for aluminum motorcycle engines. The 125SE-R's two-stroke performance can be compromised by incorrect fluids, and using plain water risks corrosion and overheating.
  • Never overfill the radiator–leave space for coolant expansion when the engine reaches operating temperature.
  • Inspect radiator hoses for cracks or bulges while the tank is removed, and replace as needed.
  • If the cooling system has not been maintained, consider flushing with distilled water before adding new coolant. Avoid harsh chemicals that could damage seals or aluminum components.
  • Check all hose clamps and the radiator cap for proper sealing to prevent leaks under pressure.

Proper coolant maintenance is vital to prevent overheating and ensure your Sherco 125SE-R delivers factory-level performance. Regular changes protect the two-stroke's power and reliabilitydon't neglect this simple but essential service task.

*Follow your owner's manual for any torque specifications and only use manufacturer-approved fluids. Failure to do so could damage the engine, void the warranty, or lead to premature wear.

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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.