How to Change the Coolant in a 2021 KTM 350SXF

Shop parts for a 2021 KTM 350SXF Dirt Bike.

Regular coolant changes are essential for the performance and longevity of your 2021 KTM 350SXF. Here is a step-by-step guide to safely and effectively replace your bike's coolant, along with important tips specific to your model.

What You Need

  • Fresh coolant (preferably KTM-recommended or high-quality motorcycle coolant)
  • An 8mm socket or wrench
  • Catch pan or bucket
  • Funnel
  • Clean rags
  • Torque wrench (recommended)
  • Distilled water (if flushing the system)

Preparation Steps

  • Ensure your engine is completely cool before starting. Hot coolant can cause severe burns.
  • Wash the area around your radiator cap and drain plug to prevent dirt from entering the system.
  • Raise your bike on a stand for better access and stability.

Step 1: Remove the Radiator Cap

  • Open the left side panel if needed for better access.
  • Slowly loosen and then remove the radiator cap to relieve any built-up pressure.

Step 2: Drain the Old Coolant

  • Locate the 8mm drain bolt on the water pump cover, usually on the right side of the engine at the bottom.
  • Place your catch pan beneath the drain bolt.
  • Remove the bolt and allow all old coolant to fully drain out.
  • If your bike has a radiator overflow hose, remove it to allow a complete drain.

Step 3: Flush the System (Optional but Recommended)

  • Reinstall the drain bolt and fill the radiator with distilled water.
  • Start the engine and let it idle for 1-2 minutes (do not rev).
  • Turn off the engine, let it cool completely, and repeat the drain process.
  • Repeat until clear water drains out, then reinstall the drain bolt.

Step 4: Add New Coolant

  • Using a funnel, slowly add new coolant to the radiator until it reaches the bottom of the filler neck.
  • Tip the bike side to side gently to help burp air bubbles from the system.
  • Reinstall the radiator cap.

Step 5: Bleed the Cooling System

  • Start the engine and let it warm up fully, allowing the coolant to circulate and further air to bleed out.
  • Shut off the engine and let it cool. Recheck the coolant level in the radiator and top up if necessary.

Step 6: Check for Leaks & Final Inspection

  • Inspect all hoses, clamps, and around the drain bolt for any leaks. Tighten as needed.
  • Make sure the radiator cap is fully seated.

Special Tips for the 2021 KTM 350SXF

  • Use only silicate-free, motorcycle-specific coolant to prevent water pump and gasket wear.
  • Regularly inspect your radiator hoses–the 350SXF is high-revving and can put additional stress on the cooling system.
  • Overheating from low coolant is a risk on tight tracks or during low-speed operation. Always check before each ride.
  • 2021 SX-F models use a pressurized system—always let the bike cool fully before opening the radiator cap.
  • Follow KTM's maintenance intervals, as early 2021 models may have OE coolant that should be replaced sooner than later.

Disposal

  • Never pour old coolant down the drain or on the ground. Take it to a local recycling center or hazardous waste collection point.

Changing your coolant is a straightforward task that protects your KTM 350SXF's engine from overheating and corrosion. Always prioritize safety—work when the bike is cool, wear gloves, and properly dispose of used coolant.

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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.