How to Change the Coolant in a 2001 Husqvarna CR50S Senior

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The 2001 Husqvarna CR50S Senior is a high-revving, liquid-cooled mini motocross bike geared for young racers who demand top performance. Regular cooling system service is critical for engine longevity, especially with its compact two-stroke motor running at high rpm. Follow these exclusive MotoSport steps for a clean, safe, and effective coolant change, tailored to your CR50S Senior.

Why Change the Coolant?

Fresh coolant not only prevents overheating but also protects internal engine passages from corrosion and mineral build-up. For high-performance bikes like the CR50S Senior, stick to the maintenance schedule–or change coolant at least once every two years or 38,000 kilometers of use, whichever comes first. Racing or hard riding warrants even more frequent changes.

What You Will Need

  • Silicone-free, motorcycle-approved coolant
  • Distilled water (for flushing)
  • Drain pan
  • Socket set/wrenches
  • Funnel
  • Gloves and safety glasses
  • Shop towels

Step-by-Step Coolant Change Guide

  • Let the engine cool: Never open the radiator cap on a hot engine. Allow the bike to cool completely—ideally an hour after last use.
  • Position the bike: Use a bike stand to keep the CR50S upright on a flat surface. Remove the seat and right-side panel for easier access to the radiator and cap.
  • Remove the radiator cap: Slowly press down and twist to release pressure before removing the cap completely.
  • Locate and remove the drain bolt: On the CR50S Senior, the coolant drain bolt is at the bottom of the water pump on the engine's right side. Position your drain pan underneath. Loosen then remove the bolt with a socket. Allow coolant to fully drain.
  • Flush the cooling system (optional, but recommended): Reinstall the drain bolt, fill the radiator with distilled water, then refit the cap. Run the engine for 3-5 minutes to circulate. Let it cool, remove the cap, and drain again. Repeat until water runs clear.
  • Inspect and clean: Wipe around the radiator neck and inspect hoses for swelling, cracks, or soft spots. Replace if needed. The CR50S Senior uses small diameter hoses, so check for internal blockages–a common issue on mini race bikes.
  • Refill with new coolant: Install the drain bolt (with fresh washer if necessary). Using a funnel, fill the radiator with high-quality, pre-mixed motorcycle coolant or manufacturer-recommended 50/50 mix. Fill until the fluid reaches the lip of the filler neck.
  • Burp the system: Start the engine with the cap off and let it idle for a few minutes. Occasionally rev gently to dislodge trapped air. Top off as needed. When bubbling subsides, refit the radiator cap securely.
  • Check the overflow reservoir: If equipped, fill the coolant reservoir to the 'max' line.
  • Test ride & inspect: After reassembly, run the engine up to temp and check for leaks. Monitor the coolant level after your next few rides–topping off if necessary.

CR50S Senior-Specific Notes

  • The CR50S Senior uses a compact aluminum radiator that may clog more easily with sediment. Flushing with distilled water is especially important.
  • The engine's small coolant capacity (typically less than one quart) means even minor leaks or air pockets can cause overheating.
  • Always use a motorcycle-specific coolant that is aluminum-safe and silicate-free to avoid internal corrosion.
  • Inspect the radiator cap seal; a worn cap can cause overheating or loss of pressure in the CR50S's tightly packaged cooling layout.

Disposal Tips

Collect old coolant in a sealed container and bring it to a local automotive recycling center. Never pour coolant onto the ground or into drains–ethylene glycol is toxic to people, pets, and the environment.

Final Checks

Regularly inspect the coolant level before rides, especially after a fresh change. Heat cycles may shift trapped air, requiring a slight top-off in the days that follow. Maintaining your cooling system is the key to reliable, safe riding for young racers and seasoned pit crews alike.

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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.