How to Change the Coolant in a 1986 Honda CR250

Shop parts for a 1986 Honda CR250 Dirt Bike.

You ride a legendary machine–the 1986 Honda CR250 was a championship contender and remains a two-stroke icon to this day. To keep your CR250 performing at its best, routine coolant changes are critical. A well-maintained cooling system protects your engine during hard rides and extends its lifespan. Follow this MotoSport guide for a smooth, mess-free coolant swap, with focus on the specifics of your classic Honda CR.

Essential Tools & Supplies

  • New coolant (50/50 distilled water & ethylene glycol, or a recommended premix designed for aluminum engines – avoid tap water)
  • 10mm socket & ratchet
  • Drain pan
  • Funnel
  • Soft brush & rags
  • Optional: replacement crush washer for drain bolt, radiator cap if original shows wear

Preparation

  • Allow your CR250 engine to cool completely–never remove the radiator cap when hot.
  • Clean around the radiator cap and water pump to keep debris out of the cooling system.
  • Place your bike on a stable stand and remove enough bodywork for easy access to the radiators and water pump. On the 1986 CR250, this typically means removing the seat, side plastics, and sometimes the fuel tank for maximum workspace.

Draining the Old Coolant

  • Set a drain pan beneath the water pump. Locate the water pump drain bolt (10mm head) at the bottom of the pump on the right engine case.
  • Loosen the radiator cap to allow airflow, but do not remove it fully yet to control the drain flow.
  • Remove the drain bolt and allow the coolant to empty completely into your pan.
  • To encourage full drainage, gently lift the front of the bike or tip it slightly toward the drain side. Carefully remove the radiator cap if you have not already.
  • If performing a full flush, re-install the drain bolt, fill with distilled water, run the engine briefly, let it cool, then drain again. Repeat until water runs clear.

Inspect & Prepare

  • Check the old coolant for signs of oil (milky color), rust, or contamination–these can reveal deeper engine or seal issues.
  • Inspect your radiator hoses for cracks or bulges, and the drain bolt washer for deformation. Replace as needed.

Refilling the System

  • Install the drain bolt with a new washer if necessary; do not overtighten (factory spec: snug plus a fraction).
  • Pour the fresh coolant slowly into the radiator neck using a funnel–stop when level reaches just below the cap sealing surface.
  • Rock the bike gently side-to-side, or squeeze the main hoses to help bubbles escape. Top off as needed.
  • Replace the radiator cap securely.
  • If your CR250 is equipped with an overflow reservoir, check and fill to the marked line.

Bleeding Air & Final Check

  • Start the engine and let it reach operating temperature at idle. Watch for leaks.
  • Rev the bike a few times and check the coolant level again as trapped air escapes. Add coolant if the level drops.
  • After the engine cools, re-inspect the level and top off if needed.

CR250 1986-Specific Notes

  • The 1986 CR250 uses a simple, relatively accessible dual-radiator system. Be sure to check both radiator cores and hoses for damage.
  • Many 1986 models may have aging radiators and hoses–inspect carefully for corrosion, cracks, or external leaks that could worsen after a coolant swap.
  • Honda specified a 50/50 mix of distilled water and ethylene glycol-based coolant for this era, but modern non-silicate, aluminum-safe coolants offer better protection for older bikes.
  • Replacing the radiator cap regularly is advised on older bikes. A weak cap can cause overheating or coolant loss.

Disposal & Safety

  • Dispose of used coolant responsibly–never pour it down the drain. Most auto parts stores or recycling centers accept it for safe disposal.
  • Rinse any spills immediately and keep coolant away from pets and wildlife; ethylene glycol is highly toxic if ingested.

With the cooling system on your 1986 Honda CR250 properly serviced, you ensure crisp throttle response and reliable power on every ride, whether you're restoring a classic or tearing up the trails. Regular coolant changes are a simple way to preserve your legendary Honda's performance for seasons to come.

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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.