How to Change the Coolant in a 2020 Sherco 125SE-R

Shop parts for a 2020 Sherco 125SE-R Dirt Bike.

Regularly changing your coolant on the 2020 Sherco 125SE-R keeps your engine performing at its peak and prevents overheating-related damage. The 125SE-R's high-revving 2-stroke engine relies on a well-maintained cooling system; following the correct process preserves the longevity and reliability of your dirt bike. The instructions below are tailored for this specific model and highlight important details every Sherco 125SE-R owner should know.

What You Will Need

  • Protective gloves and eye protection
  • Coolant approved for two-stroke off-road engines – never substitute water or unapproved fluids
  • Catch pan
  • Clean funnel
  • Socket set (including 6mm for radiator bleed screw)
  • Rags for cleanup

Preparing Your Dirt Bike

  • Make sure the engine is completely cold before starting – hot coolant can cause severe burns.
  • Position the bike vertically on a level surface. Using a stand is best for stability and easy access to the radiator and engine cases.

Draining the Old Coolant

  • Remove the radiator cap slowly. If you feel pressure release, stop and wait until it's safe, as residual pressure may cause hot fluid to spray.
  • Place a catch pan beneath the engine area.
  • Locate the coolant drain screw – on the 125SE-R, this is typically on the lower side of the water pump or is an accessible bolt along the engine casing. Loosen (do not overtighten on reassembly; torque is 10 Nm).
  • Allow coolant to drain fully from both the radiator and reservoir tank. Gently rock the bike side to side if needed to ensure all fluid exits.
  • Once empty, reinstall and tighten the drain screw.

Flushing the Cooling System (Optional but Recommended)

  • If the coolant is dirty or you suspect contamination, flush with distilled water: fill the system, run the engine briefly (not long enough to overheat), then drain again. Repeat until water runs clear.

Filling with New Coolant

  • Using a funnel, slowly add fresh coolant to the radiator until it reaches the fill neck. The 2020 125SE-R system holds approximately 1.1 liters.
  • Check the expansion container and fill to the LEVEL mark indicated.
  • With the radiator cap off, loosen the bleed screw (an M6x70 on the radiator, torque to 8 Nm) to allow trapped air to escape. Tighten the screw once only coolant escapes – no bubbles.
  • Add more coolant if the level drops.

Bleeding the System & Final Steps

  • Reinstall the radiator cap.
  • Start the bike and let it idle briefly. Watch for additional air bubbles—if the coolant drops, shut off the engine and top up again as needed.
  • Once fully heat cycled, let the bike cool completely and recheck the level in both the radiator and expansion tank. Top off as necessary.

Important Notes for 125SE-R Owners

  • Never use plain water or non-approved fluids; this can damage your engine internally.
  • Dispose of used coolant responsibly at an approved recycling center.
  • Check throttle cable play on reassembly. Cable interference during bar movement can cause erratic idling on this model.
  • Always inspect for leaks and proper operation after coolant replacement.

Keeping your 2020 Sherco 125SE-R's cooling system serviced is crucial in both day-to-day trail riding and racing. This model is known for high performance and reliability when properly maintained, so routine coolant care will ensure your Sherco performs at its best 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.