How to Change the Coolant in a 1979 Kawasaki KD80

Shop parts for a 1979 Kawasaki KD80 Dirt Bike.

Changing the coolant in your 1979 Kawasaki KD80 is key to keeping the engine running cool and reliable – especially if you ride in hot or demanding conditions. While the KD80's two-stroke engine does not have a radiator-based liquid cooling system like some larger bikes, this model does feature an oil/coolant reservoir to help prevent engine overheating. Cooling system maintenance is sometimes overlooked in smaller displacement bikes, so keeping your KD80's cooling circuit well-serviced will extend its life and performance.

What Makes the KD80 Unique?

The KD80 is a classic small-displacement dirt bike, prized for its simplicity. Unlike modern four-strokes, the 1979 KD80 has robust air cooling with an auxiliary lubrication system that sometimes utilizes a small coolant-like reservoir (common in some vintage small-displacement two-strokes). Regular maintenance of both its oil injection and any associated cooling tanks is critical. No radiator is used – so if you see references to "coolant" related to a KD80, it often means the mixture in its autolube or a non-pressurized fluid reservoir, not anti-freeze for a water-cooled engine. For bikes with confirmed aftermarket or unusual upgrades using actual liquid-cooling circuits, follow the generic liquid coolant change routine below. Always check the owner's manual or inspect your bike for modifications.

Tools & Supplies You'll Need

  • New coolant (if your bike has a liquid cooling upgrade; if original, maintain oil as specified by the manufacturer)
  • Drain pan
  • Socket wrench set
  • Funnel
  • Clean rags
  • Protective gloves – for working with oils or coolants

Step-by-Step: Changing Coolant (For Modified or Upgraded KD80s with a Radiator)

  1. Ensure the engine is cool. Remove the seat and side panels for access. Place a drain pan beneath the coolant drain bolt (usually at the lowest point on the water pump or engine).
  2. Remove the radiator cap (if present) to allow air in. Release the drain plug/bolt and let old coolant drain completely.
  3. Inspect hoses, clamps, and seals for leaks or cracks. Replace as needed before refilling.
  4. Refit the drain bolt using a new washer if possible to prevent leaks.
  5. Refill with fresh coolant using a funnel. Pour slowly to avoid trapping air bubbles. Fill to the top of the filler neck or as specified by any fill line or the service manual.
  6. "Burp" the system: With the radiator cap still off, start the engine and let it idle. Blip the throttle and gently rock the bike side-to-side to work trapped air up and out. Shut the bike down, top off coolant as necessary, then reinstall the radiator cap.
  7. Check the expansion or overflow tank (if equipped) and fill to the appropriate line.
  8. Test run: Ride until fully warmed. Check the coolant level and inspect for leaks. Top off once more after it's cooled.

Step-by-Step: Maintaining Oil/Coolant Reservoir (Original KD80 Setup)

  1. Locate the oil/coolant reservoir – usually beneath the seat or near the engine.
  2. Drain old fluid (if equipped with a drain bolt) or siphon it out carefully if no drain exists.
  3. Wipe out any residue or build-up with a clean rag.
  4. Refill with the correct oil or manufacturer-recommended lubricant. For two-strokes, use high-quality two-stroke oil. For specialty coolants (rare on KD80), follow the guidance above.
  5. Secure the cap and double-check for leaks after running the engine.

Important Notes for 1979 KD80 Owners

  • Be cautious of overheating: The KD80 relies on airflow for cooling – keep fins clean and unblocked.
  • Watch your mix: If your KD80 uses premix, always use the correct oil-to-gasoline ratio for optimal cooling and lubrication.
  • If you see a radiator, check whether your bike has been modified, as the original 1979 KD80 did not come with one.
  • Coolant leaks, unusual smoke, or inconsistent engine temps should be investigated promptly to avoid lasting damage.

With regular coolant or oil reservoir changes, your classic KD80 will stay running strong for years of trail fun.

Related Shopping Categories

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Shop Radiator Hoses for a 1979 Kawasaki KD80 Dirt Bike.

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.