How to Change the Coolant in a 2019 KTM 250SX

Shop parts for a 2019 KTM 250SX Dirt Bike.

Changing the coolant in your 2019 KTM 250SX is one of the most important maintenance steps to keep your two-stroke running cool on the track and reliable all season. KTM recommends replacing the coolant every 40–50 hours of run time to ensure top performance and protect against overheating.

What You Need

  • Park the bike on a level surface and allow the engine to cool completely. Never remove the radiator cap when hot—scalding coolant and steam can cause severe burns.
  • Tools & Supplies:
    • 10mm or 13mm wrench (drain bolt size may vary)
    • Screwdriver (for radiator shrouds, if necessary)
    • Drain pan
    • Coolant funnel
    • Fresh coolant rated for aluminum engines (avoid automotive coolant with silicates)
    • Shop towels
    • Distilled or deionized water (for flushing if needed)

Step-by-Step Coolant Change Procedure

  1. Remove the radiator cap: Let your KTM cool, then twist the radiator cap (right side of the bike, above cylinder) counterclockwise until it pops off. This releases system pressure and allows the coolant to flow out freely.
  2. Locate & remove the drain bolt: On the right side of the cylinder, find the coolant drain bolt. Place a drain pan beneath it, then use a 10mm or 13mm wrench to carefully loosen and remove the bolt. Coolant will begin draining immediately–have towels ready for spills.
  3. Drain completely: Allow all coolant to drain from the engine. To speed it up, gently tip the bike left and right. Inspect the drained coolant for dirt or contamination; flush with distilled water if necessary before refilling.
  4. Reinstall the drain bolt: Clean the drain bolt threads and reinsert it, tightening to manufacturer torque specifications to prevent leaks.
  5. Fill new coolant: Insert your funnel into the radiator neck. Slowly fill the system with your chosen high-quality dirt bike coolant, pausing to let bubbles escape.
  6. Bleed air from the system: On KTM 250SX models, there is often a small bleeder bolt atop the cylinder head. Loosen this bolt until coolant seeps out, then re-tighten–this ensures no air pockets remain in the cooling system and helps prevent hot spots.
  7. Top off & reinstall radiator cap: Continue adding coolant until the level reaches the base of the radiator neck. Replace and securely tighten the cap.
  8. Start and run briefly: Fire up your 250SX for a few minutes, then shut it off and double-check coolant level (top up as needed); inspect for any leaks at the drain bolt or hoses.

2019 KTM 250SX Ownership Tips

  • Aluminum radiators on the 2019 KTM 250SX are lightweight but require non-silicate coolant to avoid corrosion. Stick with engine-specific products to prevent clogging or premature wear.
  • Overheating Risks: Two-stroke machines, especially the 250SX, are ridden hard and may require more frequent fluid inspection if you race or ride in extreme heat. If boiling over is frequent, consider high-performance coolants.
  • Bleeder screws help remove trapped air—a unique KTM feature that should always be used during coolant changes for a bubble-free fill.
  • Inspect hoses and radiator fins for damage or mud clogging at every service. Clean debris and replace any cracked hoses to keep your cooling system efficient and reliable.

Proper coolant maintenance keeps the legendary 250SX powerplant cool under pressure and ready for every Moto finish line. Always track intervals and inspect the system as part of your regular maintenance for maximum longevity and performance.

Related Shopping Categories

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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.