How to Change the Coolant in a 1979 Yamaha IT250

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The 1979 Yamaha IT250 is a legendary enduro and features a simple air-cooled, two-stroke engine – so while it lacks a radiator and traditional liquid coolant system like more modern bikes, it’s vital for owners to thoroughly understand its unique cooling considerations. If your IT250 has been converted to use a water-cooling kit or a similar aftermarket setup (which was a rare period modification), changing the coolant is a necessary task to keep your bike running optimally on the trails. Here’s a proprietary MotoSport guide for the process, including essential tips for authentic IT250 machines.

Before You Begin: Know Your IT250

  • The stock 1979 IT250 uses an air-cooled engine. If your bike is still in original configuration, it will not require coolant or have a radiator system. Maintenance will focus on clean fins, unobstructed airflow, and proper jetting for temperature control.
  • If your IT250 has an aftermarket or custom water-cooling system installed, follow these coolant change instructions – but also consult kit-specific documentation for any additional steps required.

Tools & Supplies Needed

  • Pre-mixed motorcycle coolant (or 50/50 distilled water and coolant concentrate as specified by your kit)
  • Drain pan
  • Socket and wrench set
  • Funnel
  • Distilled water (for flushing, if needed)
  • Protective gloves and eyewear

Instructions: Changing the Coolant

  1. Allow the engine to cool fully. Never open the radiator or drain the coolant when the engine is hot – risk of severe burns and injury.
  2. Locate the radiator drain bolt and cap. On most conversions, the drain bolt will be at the lowest point of the radiator or water pump housing.
  3. Remove the radiator cap. This allows air into the system and encourages drainage.
  4. Place the drain pan underneath the radiator.
  5. Loosen and remove the drain bolt. Let the old coolant drain completely. If your system includes a reservoir tank, empty that as well.
  6. Optional: Flush the system. If it’s been more than two seasons or if the coolant is discolored:
    • Replace the drain bolt and fill the system with distilled water.
    • Start and run the engine for a few minutes to circulate water (without installing the radiator cap).
    • Let cool, then drain again.
  7. Reinstall the drain bolt, using a new sealing washer if available.
  8. Fill with fresh coolant. Pour slowly through a funnel into the radiator neck to avoid spills. Gently squeeze the hoses and tilt the bike side to side to help purge air pockets.
  9. Burb (bleed) the system. With the cap still off, start the engine and run for a few minutes at idle. Rev gently and rock the bike to expel trapped air. Top off as the level drops.
  10. Install the radiator cap securely.
  11. Check for leaks and inspect hose connections. Tighten as needed.

After the Change

  • Double-check the coolant level when the bike has cooled down completely. Top up if necessary.
  • Monitor the level again after your first long ride and add coolant if needed; air bubbles may still work their way out of the system.
  • Dispose of old coolant responsibly – it’s toxic to pets and wildlife.

IT250 Air-Cooled Essentials

  • If your IT250 is air-cooled and unrestored, focus on cleaning the cylinder and head fins regularly to ensure maximum cooling. Remove mud, debris, and oil residue that can trap heat.
  • Double-check for proper jetting and oil mix, especially if you’re riding in extreme temperature ranges – these engines are hardy but sensitive to lean mixtures and overheating.
  • Modern premix oils and clean air filters will keep the engine temps in check during aggressive riding.

Important Note for Authenticity & Collectors

  • Original, unrestored 1979 IT250s do not require a liquid coolant change. The information above is relevant only for bikes fitted with an aftermarket cooling system.
  • If unsure about your setup, inspect around the cylinder head and engine for radiators, hoses, and a coolant cap – if absent, your bike remains in original air-cooled configuration.

Got questions or need parts for your 1979 Yamaha IT250? Shop parts for a 1979 Yamaha IT250 Dirt Bike.

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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.