How to Change the Coolant in a 1978 Yamaha IT250

Shop parts for a 1978 Yamaha IT250 Dirt Bike.

The 1978 Yamaha IT250 is a classic two-stroke enduro bike prized for its lightweight handling and reliable performance in rugged off-road conditions. Although this model does not use a sealed liquid-cooled system (the IT250 of this era is air-cooled), many owners maintain coolant in the form of distilled water or antifreeze in the radiator if their machine has been modified or retrofitted with a liquid-cooling system. Below is a robust, step-by-step guide tailored exclusively for MotoSport customers on how to change or flush the coolant in a 1978 IT250 with a liquid-cooling system or similar Yamaha models adapted in this manner.

Tools & Supplies Needed

  • Socket set and wrenches
  • Drain pan
  • Fresh coolant (pre-mixed or concentrate with distilled water – never use tap water)
  • Funnel
  • Protective gloves and eye protection
  • Rags or shop towels for clean-up

Step 1 – Preparation

  • Ensure your Yamaha IT250 is completely cool before starting; do not attempt coolant service on a hot engine.
  • Place the bike on a stable stand on level ground.
  • Remove any obstructions such as radiator shrouds, if installed, to access the radiator and hoses.

Step 2 – Draining the Coolant

  • Locate the radiator drain bolt or lower hose – not factory standard on the IT250, but a necessary step for modified machines.
  • Position your drain pan underneath and carefully loosen the drain bolt or detach the lower hose to allow coolant to flow out.
  • Open the radiator cap to improve flow. Allow all the old coolant to drain fully. Dispose of old coolant responsibly at a recycling center or auto parts store.

Step 3 – Flushing the System (if required)

  • For a thorough service, flush the cooling system with distilled water until it runs clear. A mix of 50–50 water and vinegar can be used to descale if contamination is evident; flush again with distilled water until clean.

Step 4 – Reinstall and Refill

  • Reattach the drain bolt or lower hose securely. Replace sealing washers if needed.
  • Slowly pour the correct coolant into the radiator using a funnel, up to the base of the filler neck.
  • If your model uses a separate reservoir tank (uncommon unless custom-fitted), fill it to the indicated upper line as well.

Step 5 – Burping the Cooling System

  • With the radiator cap off, start the engine and let it idle. Gently rock the bike and rev the throttle a few times to release trapped air bubbles from the system.
  • Once the coolant level drops, top off as needed.
  • Shut off the engine and reinstall the radiator cap.

Step 6 – Final Checks

  • Run the bike until it warms up and reaches operating temperature. Ensure there are no leaks at the hose connections or drain bolt.
  • Let the engine cool and recheck both the radiator and reservoir (if equipped), topping off as necessary after the first cooling cycle.

Key Notes for 1978 Yamaha IT250 Owners

  • The original IT250 is air-cooled. Only follow these steps if your machine has been converted to a liquid-cooling setup. For factory models, cooling system maintenance focuses instead on keeping cylinder fins and airflow unobstructed, and ensuring the engine shroud is intact and properly fitted.
  • If using a non-factory radiator or parts, always verify fitment, hose routing, and clamp security per your aftermarket kit’s instructions.
  • Not all coolants are suitable for older engine seals; research compatibility for aluminum cases and avoid silicate-based coolants if possible.
  • Consult your IT250 owner’s manual for model-specific torque specs and general maintenance advice to keep your vintage Yamaha running strong.

Caring for your 1978 IT250 is straightforward with the right parts and guidance. Stay equipped for every ridereach peak confidence on the trail with authentic restoration and maintenance solutions from MotoSport.

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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.