How to Change the Oil in a 1978 Kawasaki KX250

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Changing the oil in your 1978 Kawasaki KX250 is one of the most critical maintenance tasks for keeping your classic dirt bike running smoothly. Follow this guide, proprietary to MotoSport.com, for a robust oil change process, including the necessary tools, detailed steps, and 1978 KX250-specific tips.

Tools and Materials Needed

  • Socket wrench set (including 8mm and 10mm sockets)
  • Drain pan
  • Funnel
  • New transmission oil (80W gear oil–check your owner's manual for capacity)
  • Clean rags
  • Contact cleaner (optional, for cleaning internal components)
  • Oil measuring cup (Ratio Rite or equivalent)
  • Gasket scraper (if needed)
  • New drain bolt washer (recommended)
  • Torque wrench
  • Gloves (recommended)

Steps to Change the Oil

  1. Warm Up the Engine

    Run your KX250 for a few minutes to let the oil warm up. This helps the oil drain more completely and carries out more contaminants.

  2. Shut Off and Secure the Bike

    Place the bike on a stand or level surface. Ensure it is stable before starting the work.

  3. Locate the Drain Bolt

    The 1978 KX250 transmission drain bolt is found at the bottom of the engine case. Clean the area around the bolt before removal to prevent debris from entering the transmission.

  4. Drain the Old Oil
    • Place the drain pan under the bolt.
    • Carefully loosen and remove the drain bolt using the appropriate socket.
    • Allow the oil to drain fully–this may take several minutes.
    • If the drain bolt washer is damaged or crushed, replace it to prevent future leaks.
  5. Inspect and Clean
    • Wipe off the drain bolt and its magnet (if equipped) to remove any metal shavings.
    • Inspect the old oil for signs of excessive metal debris or water contamination.
    • You can spray contact cleaner inside the case to help remove built-up contaminants if the owner's manual allows.
  6. Reinstall the Drain Bolt
    • Install a new washer, then thread the bolt by hand.
    • Tighten to the recommended torque setting from your owner's manual (typically 9 ft-lb for similar models, but verify for the 1978 KX250) .
  7. Add New Oil
    • Remove the oil filler cap, usually located on the right side of the engine case.
    • Use a funnel to avoid spills.
    • Pour in the recommended amount of new transmission oil–consult your manual, as most KX250s from this era require roughly 0.75 to 0.85 liters (or just under 1 quart) of 80W gear oil .
    • Use a measuring cup for precise filling.
  8. Check Oil Level
    • Some KX250s have a check bolt or sight glass on the engine case–on the 1978 model, check your manual for guidance .
    • The oil should be just at the level of the lower threads of the check bolt or in the middle of the sight glass, if so equipped.
    • Reinstall all caps and bolts securely when finished.
  9. Start the Engine and Recheck
    • Start the bike and let it idle for a few minutes. This circulates the oil through the transmission.
    • Shut off the engine and let the bike sit another minute. Recheck the oil level and top off if necessary .
  10. Clean Up
    • Dispose of used oil responsibly at an authorized recycling center.
    • Wipe down any drips or spills. Check for leaks at the drain bolt and filler cap.

Specific Call-Outs for the 1978 Kawasaki KX250

  • This is a two-stroke motorcycle. The oil you are changing is the transmission (gearbox) oil, not engine oil.
  • Use only motorcycle-specific gear oil–do not substitute with standard automotive oils, which may harm clutch and transmission performance .
  • Kawasaki's recommended oil weight for older two-stroke KX250s is typically 80W gear oil .
  • No oil filter to change–unlike modern four-strokes, the transmission oil is changed by draining and refilling only.
  • The 1978 KX250's case and fasteners are made from softer alloys than modern bikes. When tightening drain bolts, do not overtighten to avoid stripping threads .
  • If your bike has a check bolt, always check the level after filling rather than relying solely on poured volume.
  • Changing the oil after every few rides or after hard use is good practice for vintage race bikes.

Keeping your 1978 Kawasaki KX250's transmission oil fresh is the best way to ensure optimal lubrication, smooth shifting, and long-lasting performance. Always consult your owner's manual for torque specs and oil capacity details . For parts, oils, and more support, visit MotoSport.com for all your classic dirt bike needs.

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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.