How to Change the Coolant in a 2021 Beta 390 RR-S

Shop parts for a 2021 Beta 390 RR-S Dirt Bike.

If you own a 2021 Beta 390 RR-S, regular coolant changes are critical for peak performance and engine longevity. The 390 RR-S is a high-compression, liquid-cooled four-stroke dirt bike whose advanced cooling system was designed to withstand tough off-road conditions. The following proprietary guide delivers step-by-step instructions tailored specifically for this model, highlighting any unique points Beta 390 RR-S owners need to know.

Preparation

  • Ensure the engine is cool before starting–opening the radiator cap on a hot bike can cause burns.
  • Gather a drain pan, appropriate new coolant (such as pre-mixed Engine Ice or Motul), a funnel, and basic hand tools.
  • Locate the radiator cap on the left radiator (remove the right-side shroud for easier access).

Draining the Old Coolant

  • With the bike upright (use a stand if available), remove the radiator cap to release system pressure.
  • Place your drain pan under the water pump area on the lower right engine case.
  • Remove the coolant drain bolt from the water pump cover (10 mm head). Allow the coolant to drain completely.
  • Inspect the coolant color–milky or rusty fluid suggests other maintenance may be needed.
  • Replace and torque the drain bolt to manufacturer specification. Make sure the included copper washer is in good shape and reinstall it if undamaged.

Flushing the Cooling System (Recommended)

  • With the drain bolt back in, fill the radiators with distilled water via the radiator cap neck and reinstall the cap.
  • Start the engine and let it idle for several minutes to circulate the flush fluid, then turn it off.
  • Let the bike cool, then drain the water using the earlier steps. Repeat this flush process if required until draining water runs clear.

Refilling with New Coolant

  • Ensure the drain bolt is torqued properly and begin filling the radiator with your chosen coolant.
  • Pour slowly to help prevent air pockets. Fill the radiator until the fluid reaches just above the core fins inside the neck–the 2021 390 RR-S does not use radiator bleeder screws, unlike older Beta models, so careful filling and rocking the bike aids air removal.
  • Gently rock the bike side-to-side to move any trapped air bubbles to the surface. If the level drops, top off as needed.
  • Reinstall the radiator cap securely.

Final Bleed & Coolant Level Check

  • Start the engine with the radiator cap on and let the bike idle until it reaches normal operating temperature–the cooling fan should kick in during this phase. Shut off the engine and let it fully cool to ambient temperature.
  • Once cool, remove the radiator cap and recheck the fluid level. Top off if necessary, then replace the cap.
  • Check the coolant overflow reservoir (if equipped) and ensure the level is between the min and max marks.

Important Notes for 2021 Beta 390 RR-S Owners

  • No bleeder screw: Later Beta models including the 2021 390 RR-S no longer include radiator bleeder screws. Proper filling and rocking the bike as you fill will ensure air is expelled.
  • Coolant specification: Use only high-quality, motorcycle-approved, pre-mixed coolant. Avoid tap water–use distilled only for system flushes.
  • Capacity: The system takes just over 1 liter; always verify the level after the first heat cycle.
  • Fan sensor built-in: The coolant temperature sensor for the fan is preinstalled from the factory. 
  • Level check: Always check both the radiator and the reservoir after a complete cool-down–the system may need a final top-off after a short ride.

Dispose of Old Coolant Responsibly

  • Used coolant is toxic–never pour it on the ground or into drains. Take all spent coolant to your local hazardous waste collection center.

With these steps, your 2021 Beta 390 RR-S cooling system will stay healthy and your engine protected no matter where you ride.

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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.