How to Change the Coolant in a 2009 KTM 105SX: Step-by-Step MotoSport Guide

Shop parts for a 2009 KTM 105SX Dirt Bike.

Your 2009 KTM 105SX is a competition-focused mini motocrosser built for high performance and reliability. Regular coolant maintenance helps ensure that legendary KTM two-stroke engine runs cool and delivers consistent power whether you're racing or hitting the practice track. This guide breaks down a comprehensive step-by-step process to change coolant on your KTM 105SX–and highlights essential details specific to this model year.

What to Know Before You Start

  • Total coolant capacity for the 2009 KTM 105SX is 1 liter.
  • KTM specifies a 50/50 water and glycol-based coolant mix; use only distilled water if you need to mix.
  • Never use tap water, as it can cause mineral buildup in the fine radiator passages.
  • Always change coolant with a cold engine to avoid burns and ensure your safety.
  • Dispose of old coolant responsibly–never pour it down drains or on the ground.

Tools & Supplies Needed

  • Socket set or wrench (8mm is typical for drain bolts)
  • Drain pan or suitable container
  • New coolant (pre-mixed or concentrated; verify type is safe for aluminum radiators)
  • Distilled water (if mixing concentrate)
  • Rags for cleanup
  • Optional: Funnel, fresh drain bolt washer

Step 1: Draining the Old Coolant

  • Place the drain pan under the right radiator drain bolt (consult your owner's manual for exact bolt location on the lower right radiator side).
  • Remove the radiator cap on the left radiator to relieve pressure.
  • Unscrew the right radiator drain bolt and allow coolant to flow completely into the pan.
  • Inspect the old coolant for debris or discoloration–signs you may need to flush the system more frequently.

Step 2: Flushing (If Desired)

  • For a thorough cleaning, refill the system with distilled water only and repeat the draining step.
  • This will help remove residual old coolant and contaminants.

Step 3: Filling the Cooling System

  • Reinstall the right-side radiator drain bolt, using a fresh sealing washer if needed.
  • Pour about 0.5 liters of new coolant into the radiator.
  • Remove the vent bolt at the top of the right radiator.
  • Continue slowly adding coolant until it emerges at the vent hole without bubbles, then reinstall the vent bolt immediately to prevent air from re-entering the system.
  • Top up coolant in the left radiator until you see the level about 10mm above the radiator fins.

Step 4: Bleeding the System

  • Start the engine briefly with the radiator cap off; let it idle and gently tap the hoses to encourage any trapped air to escape.
  • Top up coolant as needed, then install the radiator cap securely.

Step 5: Final Checks & Test Ride

  • Warm up the engine and inspect for leaks at the drain bolt, vent bolt, and along radiator hoses.
  • After a short and careful test ride, recheck the coolant level and top off if necessary. Re-inspect for leaks.

Model-Specific Tips: 2009 KTM 105SX

  • This model holds exactly 1 liter of coolant when totally empty so do not overfill after burping the system.
  • The 105SX uses a high-revving two-stroke with a relatively small coolant reservoir–regularly monitor levels during hot riding conditions.
  • If you ride in extreme temperatures, consider a high-performance or race-spec coolant endorsed for KTM aluminum radiators.
  • While working on your cooling system, visually inspect all hoses and clamps for cracking or leaks, replacing aging components as needed for peace of mind.

Keeping your 2009 KTM 105SX's coolant fresh ensures maximum engine protection and performance. Stay ahead on maintenance so you can focus on what matters–riding at your best.

Related Shopping Categories

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Shop Radiator Hoses for a 2009 KTM 105SX 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.