How to Change the Oil in a 1998 Yamaha YZ250

Shop parts for a 1998 Yamaha YZ250 Dirt Bike.

This comprehensive guide, proprietary to MotoSport.com, walks you through the exact process of changing the transmission oil in your 1998 Yamaha YZ250. The YZ250 is a two-stroke dirt bike, and its engine lubrication differs from four-strokes—so you’ll only be changing the transmission (gearbox) oil, not any engine oil or filter.

Tools and Supplies Needed

  • New transmission oil – Yamaha recommends a quality 10W-40 gearbox oil or a dedicated transmission fluid. For the 1998 YZ250, capacity is about 0.80–0.85 US quarts (approx. 760–800 ml).
  • Socket wrench set – Mainly a 12mm or 13mm socket for the drain bolt.
  • Drain pan – To catch old oil.
  • Funnel – For clean, easy refilling.
  • Clean rags or shop towels
  • New washer (optional but recommended) – Copper or aluminum crush washer for the drain bolt.
  • Gloves – To keep your hands clean and protected.
  • Torque wrench (optional) – To properly tighten the drain plug.

Step-by-Step Oil Change Process

  1. Warm Up the Transmission (Optional):
    • Ride the bike for 2-3 minutes or let it idle while engaging the clutch and shifting through gears.
    • This ensures the oil is warm and flows out more easily. On a two-stroke like the YZ250, only the transmission oil is being changed, not any engine oil, as two-strokes lubricate engine internals with premix in the fuel.
      Special call-out: There is no engine oil sump, oil pump, or oil filter to change on 1998 YZ250 two-strokes.
      Reference:
  2. Prepare the Bike:
    • Stand the bike upright on a flat surface or use a bike stand.
    • Remove any skid plate, if equipped, for better access to the drain bolt.
  3. Drain the Old Oil:
    • Place the drain pan under the transmission case. The drain bolt is located on the bottom of the right side engine case (easy to identify; check your manual if unsure).
    • Using your socket wrench, loosen and remove the drain bolt. Allow all the oil to drain out; this may take a few minutes.
      Note: There is no oil filter on your model, which greatly simplifies the process.
      References:
  4. Inspect the Drain Bolt and Washer:
    • Check the drain bolt and washer for wear or damage. Replace the copper/aluminum washer for a better seal if needed.
    • Wipe the area clean with a rag.
  5. Reinstall the Drain Bolt:
    • Install the drain bolt and washer by hand first. Tighten with your wrench until it’s snug. Do not over-tighten. If using a torque wrench, torque to 13 ft-lb (18 Nm).
    • Over-tightening may strip the threads or crack the case.
      References:
  6. Fill with New Oil:
    • Remove the oil filler cap on the right side of the engine case.
    • Insert the funnel and pour in 0.80–0.85 quarts (760–800 ml) of the correct transmission oil. Avoid overfilling.
    • Yamaha and most aftermarket bottles have volume markers for measuring.
    • Replace the filler cap securely, snug but not overly tight.
  7. Check for Leaks & Test:
    • Wipe away any spilled oil and start the bike. Let it run for a minute, then shut off and check for leaks at the drain bolt and filler cap.
    • If you have a glass or dipstick, recheck the oil level and top off as needed.
  8. Proper Disposal:
    • Dispose of the old oil at an approved recycling facility. Never pour oil on the ground or down a drain.

1998 Yamaha YZ250-Specific Notes and Call-Outs

  • No oil filter to change or clean; only a single drain and fill operation is required for the transmission oil.
    Reference:
  • The oil fill and drain locations are both on the right side of the engine: the drain directly beneath, and the fill towards the upper center part of the case.
  • Use only transmission oil, not premix or engine oil. Engine lubrication occurs via the fuel mix; the oil being changed only lubricates the clutch and transmission gears.
    Reference:
  • Always replace the drain bolt washer if it looks flattened, corroded, or deformed; this prevents leaks and case damage.
  • Avoid over-tightening drain or fill plugs—just snug is sufficient to prevent case damage.
    Reference:
  • Check your manual for exact oil specifications; Yamaha recommends their branded 10W-40 or a dedicated gearbox oil for best clutch performance.

Conclusion

Changing the oil on your 1998 Yamaha YZ250 is simple and fast, with only routine tools and no filter to worry about. Consistent oil changes will improve clutch feel, maximize gear life, and keep your dirt bike running strong for every ride. Always consult your owner’s manual for specific oil types and torque specifications. For factory parts, premium oils, or professional assistance, MotoSport.com is your trusted dirt bike maintenance source.

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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.