How to Change the Coolant in a 2019 Sherco 125SE-R: Complete MotoSport Guide

Shop parts for a 2019 Sherco 125SE-R Dirt Bike.

Maintaining your 2019 Sherco 125SE-R's cooling system is essential for reliable two-stroke performance–especially given the bike's high-strung engine and off-road focus. Below, MotoSport walks you through a robust, model-specific coolant change process to keep your Sherco running cool on every ride.

Items You'll Need

  • Fresh coolant (consult your owner's manual or use a high-quality motorcycle-specific coolant)
  • Socket set and screwdrivers
  • Drain pan
  • Clean funnel
  • Protective gloves
  • Shop rags

Step-by-Step Coolant Change

1. Ensure the engine is completely cool–never open the radiator cap on a hot engine.

2. Remove seat and plastics as needed for easier access to the radiator fill cap and coolant hoses.
On the 125SE-R, removing the seat is quick: loosen the mounting bolt at the rear and slide the seat backward. Remove side shrouds if they block access to the radiator fill neck.

3. Prepare to drain coolant:
- Position a drain pan under the lower water pump area on the right side of the engine.
- Loosen (but don't remove) the radiator cap to avoid creating a vacuum during draining.
- Identify the coolant drain bolt. On the Sherco 125SE-R, this is typically located at the lowest point of the water pump cover.

4. Drain the system:
- Remove the coolant drain bolt and let the old coolant flow into your pan.
- To maximize drainage, gently lean the bike from side to side.
- Inspect the old coolant for oil or debris–contamination can indicate a water pump seal issue.

5. Flush (optional but recommended):
If the coolant was discolored or contaminated, flush the system by replacing the drain bolt and filling with distilled water. Run the engine briefly, allow it to cool, then drain and repeat if needed. Never use tap water due to mineral deposits.

6. Reinstall the drain bolt and ensure it's tightened to factory torque specifications.

7. Fill with new coolant:
- Pour fresh coolant slowly into the radiator via the filler neck, using a funnel to prevent spills.
- The Sherco 125SE-R doesn't have a separate overflow tank to fill; just top up the radiator until fluid reaches the base of the filler neck.
- Squeeze and release the upper and lower radiator hoses to help purge trapped air.

8. Bleed air from the system:

  • With the radiator cap off, start the engine and allow it to idle until operating temperature is reached.
  • Watch for air bubbles rising from the radiator neck–signs of trapped air escaping.
  • Once bubbling stops and the coolant level stabilizes, carefully top up as needed and reinstall the radiator cap.

9. Reassemble:
Reinstall plastics and the seat. Clean off any spilled coolant. Check for leaks around drain bolt and hose connections.

10. System check:

  • After your first ride, let the engine cool completely and check the coolant level again. Top off if necessary.
  • If the level repeatedly drops or cloudy coolant appears, further inspection may be needed.

2019 Sherco 125SE-R Owner Notes

  • This model features a compact two-stroke cooling system that heats and cools rapidly. Regularly monitor fluid levels, particularly after long or aggressive rides.
  • Check for leaks at the water pump seal–milkiness in coolant can signal a worn bearing or seal.
  • Torque specs for bolts, including the water pump drain, should follow Sherco recommendations to avoid stripping (often 6–9 Nm for small bolts).
  • For high-performance or extreme-climate riding, consider a premium high boiling-point coolant for even better protection.

Routine coolant servicing protects your 125SE-R's engine investment, giving you more confidence on every trail ride. For genuine replacement parts, gaskets, and performance upgrades, visit MotoSport to keep your Sherco running at its best.

Related Shopping Categories

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Shop Temperature Sensors for a 2019 Sherco 125SE-R Dirt Bike.

Shop Tools for a 2019 Sherco 125SE-R Dirt Bike.

Shop Radiator Hoses for a 2019 Sherco 125SE-R 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.