How to Change the Coolant in a 2025 KTM 150SX: Step-by-Step Guide

Shop parts for a 2025 KTM 150SX Dirt Bike.

Changing the coolant in your 2025 KTM 150SX is essential maintenance, ensuring optimal engine performance and protection against overheating. The cooling system on the 150SXlike other KTM two-strokesuses high-performance coolant, and proper service extends the life of internal components. This guide is developed specifically for MotoSport.com customers and covers tools, procedures, and special notes for this model year.

What You Will Need

  • New coolant (using a quality motorcycle-specific formula is recommended for KTM)
  • 8mm socket or wrench
  • Drain pan or container
  • Funnel
  • Shop towels for cleanup
  • Protective gloves and eyewear (coolant is harmful to eyes & skin)

Pre-Service Preparation

  • Ensure the bike is on a stable stand and the engine is cool to the touch – never open the radiator cap on a hot engine.
  • Wear eye protection, and immediately rinse with water and seek medical attention if coolant contacts your eyes.
  • Dispose of old coolant according to local regulations; do not pour it on the ground or down drains.

Step 1: Remove the Radiator Cap

  • With the engine cool, carefully remove the radiator cap by turning it counter-clockwise.
  • Do not force the cap; use light downward pressure if necessary.

Step 2: Locate and Remove the Water Pump Drain Bolt

  • Locate the 8mm drain bolt on the water pump covergenerally on the lower right-hand side of the engine.
  • Position your drain pan under the bolt, then remove the bolt to let old coolant flow out.
  • Temporary tip: Remove the radiator cap fully if you did not do so in Step 1 to improve drain flow.

Step 3: Drain the Coolant

  • Let the coolant fully drain out, then inspect old fluid for contamination or discoloration. Replace the bolt and torque it to OEM spec after drainage is complete.

Step 4: Refill with Fresh Coolant

  • With the bike upright, use a clean funnel to fill the radiator completely to the lower edge of the filler neck.
  • Gently tap hoses to release any trapped air pockets.

Step 5: Bleed and Check Coolant System

  • Start the engine and let it idle for several minutes with the radiator cap loosely in place. Carefully monitor coolant level as air escapesadd more coolant if necessary.
  • Once no bubbles are rising and the fluid level remains steady, shut off the bike, allow it to cool, then top off if needed and refit the radiator cap securely.

Step 6: Check for Leaks and Test Ride

  • Inspect all connections and ground under the bike for leaks.
  • After a short test ride, let the bike cool, then check the coolant level again. Top up if necessary.

Model-Specific Notes: 2025 KTM 150SX

  • This updated 150SX may feature tighter radiator packaging and minor hose routing changesensure all hoses are routed without kinks, and secure using OEM clamps as specified in the owner's and setup manuals.
  • Use only manufacturer-recommended coolants to avoid damage to magnesium engine parts typical of KTM small-bore two-strokes.
  • If your bike has a new T-pipe or updated fastener hardware, always use the correct tool size and torque settings to avoid over-tightening and stripping threads. Consult your owner's manual for specifics.
  • Rinse thoroughly and change clothing immediately if coolant spills on skin, as modern coolants can be more aggressive to materials and flesh.

Safety Reminder

Never open the radiator cap while the system is hot or pressurized. Dispose of used coolant responsibly. Regular coolant changes – typically once per season for racers and at least every second season for casual riders – keep your 2025 KTM 150SX running reliably on track or trail.

Related Shopping Categories

Shop Radiators for a 2025 KTM 150SX Dirt Bike.

Shop Coolant for a 2025 KTM 150SX Dirt Bike.

Shop Temperature Sensors for a 2025 KTM 150SX Dirt Bike.

Shop Tools for a 2025 KTM 150SX Dirt Bike.

Shop Radiator Hoses for a 2025 KTM 150SX 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.