How to Change the Coolant in a 1981 Suzuki RM80

Shop parts for a 1981 Suzuki RM80 Dirt Bike.

Properly maintaining the cooling system on your 1981 Suzuki RM80 is crucial for peak performance and engine longevity–especially given the age and unique characteristics of this classic air-cooled two-stroke. Though the RM80 of this era relies primarily on air cooling, many riders have fitted aftermarket liquid cooling kits, so always check whether your specific bike uses a radiator before starting service. If you have a factory RM80 without modifications, it will not have a radiator and coolant system. Owners with aftermarket coolant systems or those working on a swapped engine, follow these steps for a complete coolant change tailored for MotoSport customers.

Preparation and Safety

  • Ensure the bike is completely cool to prevent burns.
  • Place the bike securely on a stand or block.
  • Gather: the correct type of coolant (typically a pre-mixed motorcycle coolant or a 50/50 mix of distilled water and motorcycle antifreeze), a drain pan, basic hand tools, and safety gloves.

Drain the Old Coolant

  • Remove any bodywork or skid plate if necessary to access the water pump and radiator.
  • Remove the radiator cap to relieve system pressure.
  • Locate the coolant drain bolt at the bottom of the water pump. Place your drain pan underneath and remove the bolt. Let all coolant drain thoroughly. 
  • Once most coolant is out, gently rock the bike to ensure full drainage. If fitted, disconnect the lowest radiator hose to release any remaining coolant. 

Flush the Cooling System (Recommended)

  • With the drain bolt out, pour distilled water through the radiator filler neck. Allow it to fully drain. Repeat until the water runs clear. 
  • Avoid tap water due to potential mineral deposits.

Refill with Fresh Coolant

  • Reinstall and tighten the drain bolt securely, using a new sealing washer if possible. 
  • Slowly pour your fresh coolant into the radiator up to the base of the filler neck. 
  • Check for leaks around the drain area.

Bleed the System of Air

  • With the cap off, start the engine and let it idle for several minutes. Gently blip the throttle and carefully rock the bike side-to-side. This process helps air bubbles escape–called burping the radiator. 
  • Keep an eye on the coolant level and top off as needed so the radiator stays full. 
  • Once air is cleared and the fluid level remains steady, reinstall the radiator cap.

Finishing Touches and Inspection

  • Let the bike cool completely.
  • Check the coolant level once more–top off if needed. 
  • Inspect all connections for leaks. Reinstall any removed bodywork.
  • Dispose of used coolant responsibly through a recycling center or auto parts store. 

Important Owner Notes for the 1981 Suzuki RM80

  • The 1981 RM80 originally does not come equipped with a liquid cooling system. The above steps apply if your bike has been retrofitted with a cooling system, which became common on race-modified or rebuilt bikes.
  • If your RM80 is stock (air-cooled), regular cleaning of cooling fins and cylinder is crucial. Use compressed air and a brush, not coolant.
  • Always verify your bike's setup before performing any maintenance.
  • Consult your MotoSport customer support team if you're uncertain about identifying or servicing aftermarket components.

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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.