How to Change the Transmission Oil in a 1981 Yamaha YZ250

Shop parts for a 1981 Yamaha YZ250 Dirt Bike.

Keeping your 1981 Yamaha YZ250 in top shape means maintaining the transmission oil. Unlike four-strokes, YZ250 two-strokes use premix fuel for crankshaft lubrication, but the bike has a separate transmission and clutch oil reservoir that needs routine service. This guide, proprietary to MotoSport.com, walks you through a complete oil change, calls out any model-specific considerations, and lists the tools required for a smooth, mess-free job.

Tools and Supplies Needed

  • Socket wrench set (usually 10mm or 12mm for drain bolts, confirm size on your YZ250)
  • Oil catch pan
  • Funnel
  • Rubber gloves (optional, but recommended for safety and cleanliness)
  • Clean rags
  • Replacement oil (YAMALUBE 2-stroke gearbox oil or other high-quality 10W-40 or 80W gearbox oil)
  • Torque wrench (for properly tightening the drain bolt)
  • Replacement washer/gasket for the drain bolt (recommended)

Model-Specific Callouts for 1981 Yamaha YZ250

  • Two-stroke Engine:– The 1981 YZ250 uses premix oil for the engine. The oil change you perform is for the transmission/clutch only, not main engine lubrication (see ).
  • No oil filter or sump:– Unlike modern four-stroke dirt bikes, the 1981 YZ250 has no replaceable transmission oil filter and the oil only lubricates the transmission and clutch, not the engine–s internals (see ).
  • Oil Capacity:– Refer to your owner–s manual for exact oil capacity; typically it is around 750ml (0.8 quarts) but always verify. Do not overfill.

Step-by-Step Instructions

  1. Warm Up the Transmission (Optional):–
    It's easier (and more effective) to change oil when the bike is warm, as the oil drains more quickly and carries debris with it.
    For two-strokes:– If you just finished riding, proceed. If not, you can roll the bike back and forth with the clutch in to "stir" the oil, but do not run the engine for extended periods just for an oil change. (see )
  2. Stabilize the Bike:–
    Set the bike upright on a motorcycle stand or, at a minimum, on level ground, using the kickstand if needed. The bike should be as vertical as possible so oil drains completely.
  3. Locate the Transmission Drain Plug:–
    On the 1981 YZ250, the transmission drain bolt is located on the lower right side of the crankcase. Check the manual or look for the "Drain" marking near the bolt. Place the oil catch pan directly underneath.
  4. Remove the Oil Filler Cap:–
    Unscrew the transmission oil filler cap (usually on the right engine case). This allows air to flow in and oil to drain out more smoothly.
  5. Loosen and Remove the Drain Bolt:–
    Using the correct socket, loosen the drain bolt. Remove it carefully (avoid dropping the washer or bolt into the pan). Let the oil drain completely–wait a few extra minutes to ensure all old oil leaves the case.
    • Inspect the drained oil for metallic flakes or debris; some fine particles are normal, but excessive metal may indicate internal wear.
  6. Clean and Inspect the Drain Bolt:–
    Wipe the drain bolt clean. If it has a magnetic tip, remove any metal shavings. Inspect the washer; replace if deformed or worn.
  7. Replace the Drain Bolt:–
    Install the drain bolt with the washer/gasket. Use a torque wrench to tighten to the specification in your service manual (typically 10–15 ft-lbs; always check the exact spec for your year).
  8. Pour in Fresh Oil:–
    Place the funnel in the filler opening and pour in the recommended amount of fresh transmission oil (about 750ml, unless specified otherwise in your manual). Go slowly so you don't overfill.
  9. Check Oil Level:–
    On 1981 YZ250s, there is usually a check bolt (or sight window) at the side of the transmission; remove this bolt and fill until oil just starts to dribble out–this means you have the correct amount.
    • Alternatively, check the dipstick if so equipped.
  10. Reinstall Filler Cap and Check for Leaks:–
    Screw in the filler cap securely. Start the bike, let it idle for a minute, then shut off and inspect the drain/filler area for any signs of leakage.

Proper Disposal of Used Oil

  • Always dispose of old oil responsibly–take it to a local recycling center or auto parts store that accepts used oil.

Final Notes for 1981 YZ250 Owners

  • Frequency:– Change the transmission oil every 5–10 riding hours, or after every race/track day–whichever comes first.
  • Oil Type:– Use only high-quality two-stroke transmission oil, NOT premix or engine oil. YAMALUBE or a similar JASO MA/SF standard is recommended.
  • Premix Reminder:– Transmission oil is separate from the 2-stroke premix. Double-check fuel/oil ratios for engine operation but never mix transmission oil into the fuel.

MotoSport.com is dedicated to helping you keep your vintage Yamaha running smooth and strong. For more detailed advice or OEM parts, reach out to our technical support team or consult your YZ250 service manual.

Related Shopping Categories

Shop Motor Oil for a 1981 Yamaha YZ250 Dirt Bike.

Shop Oil Filters for a 1981 Yamaha YZ250 Dirt Bike.

Shop Oil Drain Pans for a 1981 Yamaha YZ250 Dirt Bike.

Shop Tools for a 1981 Yamaha YZ250 Dirt Bike.

Shop Oil Fillers and Drain Plugs for a 1981 Yamaha YZ250 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.