How to Change the Oil in a 1978 Yamaha IT250

Shop parts for a 1978 Yamaha IT250 Dirt Bike.

Changing the oil in your 1978 Yamaha IT250 is a critical piece of maintenance, ensuring smooth operation and longevity of your dirt bike’s transmission. Even though the IT250 is a two-stroke, which uses a premix of oil and fuel for the engine, it requires periodic transmission oil changes to keep the clutch and gears lubricated and running efficiently. Follow this detailed how-to, proprietary to MotoSport.com, on safely and effectively changing the oil in your classic Yamaha dirt bike.

Tools and Supplies Needed

  • Socket wrench set (8mm-14mm, typically 12mm for the drain plug)
  • Drain pan to catch old oil
  • Funnel for refilling
  • Clean shop rags
  • Flathead screwdriver (optional, for loosening stubborn bolts)
  • Measuring cup for new oil
  • Gloves (recommended for cleanliness)
  • New transmission oil (SAE 10W/30 “SE” name-brand motor oil as recommended by Yamaha)

Before You Begin

  • Make sure the bike is cool to avoid burns from hot engine parts.
  • Park on a level surface and use a center stand if you have one, or secure the bike upright.
  • Clean the area around the drain plug and filler cap with a rag to prevent dirt from entering the transmission case.

Step-by-Step Oil Change Process

  1. Locate the Drain Plug
    The drain plug for the transmission is positioned beneath the engine, typically toward the left side. The transmission oil filler plug is located above the kick starter. Place your drain pan directly beneath the plug to catch the old oil.
    Model-Specific Call-Out: On the 1978 IT250, ensure you do not confuse the crankcase drain with the transmission drain plug. Only the transmission oil is being changed in this procedure.
  2. Remove the Drain Plug
    Use your socket wrench to slowly loosen the drain plug. As it comes out, let the oil flow into the pan. Allow several minutes for complete drainage.
  3. Inspect the Drain Plug
    Once removed, inspect the drain plug for metal shavings. Some fine metallic particles are normal but excessive material may indicate internal wear.
  4. Reinstall the Drain Plug
    Wipe the plug clean, check the condition of the sealing washer, and reinstall using your socket wrench. Do not overtighten to prevent stripping the threads or damaging the case.
  5. Remove the Filler Plug
    The transmission oil filler plug is found just above the kick starter. Remove it with your socket or by hand.
  6. Add New Oil
    Using your funnel and measuring cup, pour in the recommended amount of oil (refer to your owner's manual, but typically around 750ml for the IT250). Use only a high-quality SAE 10W/30 “SE” type motor oil.
  7. Check the Oil Level
    The oil level should be checked at the specified inspection port or fill hole. The oil should reach, but not overflow, the bottom edge of the fill hole. Add more oil if needed, a little at a time.
  8. Replace the Filler Plug
    Wipe away any spilled oil and securely reinstall the filler plug.
  9. CLEAN UP
    Dispose of the used oil responsibly. Wipe down the area around the plug and check for leaks with the bike upright.
  10. Final Inspection
    Start the engine and let it idle for a minute. Check for oil leaks at the drain and filler plugs. Recheck the oil level after the engine has run, topping up if necessary.

Special Considerations for the 1978 Yamaha IT250

  • This bike requires pre-mix fuel for the engine and separate transmission oil. Do not attempt to use 4-stroke engine oil in the fuel tank, and do not use 2-stroke premix in the transmission case.
  • Transmission oil capacity change is listed in the owner’s manual. Always measure oil volume rather than relying solely on sight glass or dipstick, as this generation does not typically offer a sight window.
  • Inspect gaskets and washers any time you open the drain or fill plugs; replace if damaged to prevent leaks.
  • Recommended Oil: Use quality, modern substitutes meeting SAE 10W/30 “SE” specification if original Yamaha lubricants are not available.

Helpful Tips

  • Run the engine for a few minutes before draining to warm the oil, which helps it flow out more thoroughly.
  • Always use a new crush washer on the drain bolt for best sealing.
  • If you ride aggressively or in harsh conditions, consider changing the oil more frequently than the manual suggests.

That’s it. With a few hand tools, attention to detail, and quality oil, you’ll keep your 1978 Yamaha IT250 shifting smoothly and ready for the next ride. For parts, tools and more vintage bike resources, trust MotoSport.com—Your Ride Starts Here.

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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.