How to Change the Transmission Oil in a 1998 Yamaha PW50

Shop parts for a 1998 Yamaha PW50 Dirt Bike.

Changing the transmission oil in your 1998 Yamaha PW50 is vital to keep the bike running smoothly and prevent premature transmission wear. This guide, proprietary to MotoSport.com, details everything you need, along with important steps and model-specific notes for the PW50.

Tools and Materials Needed

  • 12mm socket or wrench
  • Measuring cup (preferably marked to 0.30 L)
  • Oil funnel
  • Drain pan
  • Fresh transmission oil (Yamalube or approved equivalent, see below for quantity)
  • Crush washer (replace with each change)
  • Rubber gloves
  • Rags for cleanup

Recommended Transmission Oil and Quantity

  • Oil Type:– Use only the recommended transmission oil. Yamalube is suggested for optimal performance and protection.
  • Capacity:– 0.30 Liters (0.32 US qt, 0.26 Imp qt) of transmission oil for the 1998 Yamaha PW50. Do not overfill or underfill.
    Reference: PW50/K/K2 Yamaha Manual

Step-by-Step Guide

  1. Warm Up the Engine
    • Briefly run the PW50 for 2-3 minutes to warm the oil, making it flow out easier and ensuring a more complete drain.
      This step is recommended for all PW50s to help suspend particulates in the oil for removal.
  2. Position the Bike
    • Turn off the engine and place the bike on a level surface with the wheels securely on the ground or a stand.
    • Ensure the transmission area and drain bolt are easily accessible.
  3. Prepare to Drain
    • Put on gloves. Place a drain pan directly beneath the transmission drain bolt (left side, bottom of engine near the footpeg).
    • If your model has excessive dirt, wipe the area first to prevent contamination.
  4. Remove the Drain Bolt
    • Use your 12mm socket to loosen and remove the drain bolt. Caution:– The oil may be hot.
    • Allow all oil to fully drain into the pan. Inspect old oil for excessive debris, which could indicate internal wear.
    • Remove the old crush washer from the bolt (always replace it to prevent leaks).
  5. Reinstall the Drain Bolt
    • Install a new crush washer onto the bolt.
    • Thread the bolt back in by hand, then use your wrench to tighten to 14 Nm (10 lb·ft).
      Do not overtighten—using the factory torque is crucial on the lightweight aluminum cases.
  6. Add Fresh Oil
    • Remove the oil fill cap on the right-side engine cover.
    • Using a measuring cup, pour exactly 0.30 L of the recommended oil into the transmission through a funnel.
    • Reinstall and tighten the fill cap securely.
  7. Check for Leaks
    • Start the engine and let it idle for a minute.
    • With the bike still on a level surface, inspect the drain and fill areas for leaks.
    • Wipe away any drips and tighten the drain bolt slightly if a small leak appears (never over-torque).
  8. Dispose of Old Oil Properly
    • Never pour used oil on the ground or into regular trash.
    • Bring it to a certified recycling center or an auto parts shop that accepts used oil.

Model-Specific Notes for the 1998 Yamaha PW50

  • All Yamaha PW50s (including 1998) use a two-stroke engine:– The transmission oil change is completely separate from the two-stroke injector oil. Maintain proper levels in both for reliable operation.
  • Change interval:– For a new bike, change after the first month of use, then at six months, and annually thereafter, unless more frequent riding or racing is involved.
  • Transmission oil fill quantity and torque:– Never exceed 0.30 L and always torque the drain bolt to exactly 14 Nm. Overfilling or under-torquing can result in leaks or internal damage.
  • Always use a new crush washer:– Re-using old washers can cause transmission oil leaks. Crush washers are inexpensive and vital for sealing.
  • OEM-recommended oil is best:– While alternatives like Valvoline may work, always default to Yamaha's Yamalube for the safest and best long-term protection, as recommended by factory and most experienced mechanics.

Final Tips

  • Mark the date or engine hour after each service to stay on schedule for the next change.
  • Inspect the oil coming out–milky, metallic, or sludgy oil could indicate seal, water ingress, or transmission wear that should be addressed immediately.
  • Follow all manufacturer torque specs from the factory service manual to avoid damaging the cases or hardware.

By following this guide, Yamaha PW50 owners can be confident they are keeping their bike's transmission well protected for years of trouble-free riding. 1998 PW50s require only basic tools but careful attention to oil quantity, correct part torque, and using a new crush washer with every change.

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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.