How to Change the Coolant in a 2022 KTM 125SX

Shop parts for a 2022 KTM 125SX Dirt Bike.

Maintaining your 2022 KTM 125SX is critical to keep it running strong – and changing the coolant is a vital part of your regular maintenance routine. Here is a comprehensive, model-specific guide from MotoSport to changing the coolant on your KTM 125SX, along with important tips all owners should know about this two-stroke MX machine.

Tools & Supplies Needed

  • Fresh 50/50 premixed motorcycle coolant (KTM recommends a ready-to-use coolant that contains ethylene glycol)
  • 8mm socket or T-handle
  • Drain pan or container
  • Funnel
  • Torx bit set (optional for shrouds/guards, if needed for access)
  • Clean shop towels or rags

Preparation

  • Ensure the bike is completely cool before starting – never open a radiator cap on a warm engine, as hot coolant under pressure can cause burns.
  • Place the bike on a stand, keeping it level and stable.

Step 1: Remove the Radiator Cap

  • Unscrew and remove the radiator cap. It may have a child-proof type safety lock; press down and twist to remove as needed.

Step 2: Locate & Remove the Drain Bolt

  • On the 2022 KTM 125SX, the coolant drain bolt is located on the lower side of the water pump cover, typically on the right side of the engine, easily accessed with an 8mm socket.
  • Position the drain pan beneath the bolt, loosen it, and allow all the old coolant to fully drain out. Open the left-side radiator cap during this step for faster draining.

Step 3: Inspect Bolts & Seals

  • Check the drain bolt & its sealing washer for wear. Replace the washer if damaged, as leaks can develop otherwise.

Step 4: Reinstall the Drain Bolt

  • Once flow has stopped, reinstall the clean drain bolt (with fresh washer if needed) and torque it to spec: 11.1 lbf–ft (15 Nm) for KTM 125SX models.

Step 5: Refill the Cooling System

  • With the bike upright, use a clean funnel to refill the radiator with the recommended coolant until full – the 2022 KTM 125SX requires approximately 1.2 liters (1.3 US quarts).

Step 6: Bleed the System

  • Slowly rock the bike side to side to help eliminate trapped air bubbles. Squeeze the radiator hoses gently as you add coolant. Fill right up to the radiator neck.

Step 7: Final Reassembly & Check

  • Install the radiator cap tightly.
  • Start the bike and let it idle until the engine is fully warmed up (thermostat open). Shut off, allow to cool completely, then re-check the coolant level – top up if needed.
  • Dispose of old coolant responsibly.

Important Notes Specific to 2022 KTM 125SX Owners

  • This bike features KTM's advanced cooling system for high-intensity motocross use. KTM specifies the use of a high-quality, ready-mixed coolant with a freezing point of at least –22°F (–30°C) and included corrosion inhibitors for magnesium/aluminum components.
  • If your machine regularly runs in high-heat, muddy, or sandy environments, inspect your radiator guards and cooling fins for debris and damage as part of this job.
  • Never mix silicate-based green coolants with orange or pink OAT coolants – stick with one compatible type for best gasket life.
  • If air remains trapped, the 125SX may overheat quickly. Always double-check for proper coolant fill and monitor temperature after your first ride.

When Should You Change Coolant?

KTM recommends changing the coolant at least once per season, or more frequently for intensive racing and high hours. Inspect during regular maintenance as coolant can degrade or become contaminated by scale over time.

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Shop Radiator Hoses for a 2022 KTM 125SX 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.