How to Change the Oil in a 1999 Yamaha PW80

Shop parts for a 1999 Yamaha PW80 Dirt Bike.

Routine oil changes are essential for keeping your 1999 Yamaha PW80 running smoothly. This step-by-step guide, proprietary to MotoSport.com, will walk you through the process, including model-specific tips and all the tools you'll need. The PW80 features both a two-stroke auto-injection system for engine lubrication and a separate transmission oil system, so be sure you're addressing the correct oil system for routine maintenance.

Tools and Supplies Needed

  • Socket set (10mm in particular for seat removal)
  • Socket wrench
  • Oil drain pan
  • Funnel
  • Rags (for cleanup)
  • Yamaha-recommended transmission oil (SAE 10W30, not to be substituted with “CD” diesel or “Energy Conserving II” or higher)
  • Measuring cup with milliliter (ml) or quart markings
  • Gloves (optional, for a cleaner job)

PW80-Specific Callouts

  • The oil tank for the auto-injector two-stroke oil is under the seat, accessed by removing two 10mm nuts under the rear fender

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  • For changing the transmission oil (the “oil change” most commonly maintained), reference the oil fill is on the left-side cover. You do not need to premix gas and oil–the injection system does this for you (unless it’s been removed or has a block-off kit installed)

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  • The oil capacity for a change is 0.65L (650ml, 0.69 US quart)

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Step-by-Step Instructions

  1. Warm Up the Engine
    • Start the PW80 and let it idle for a few minutes. Warm oil will flow more freely, ensuring a more thorough drain.
  2. Access the Drain Plug
    • Locate the oil drain bolt under the engine. Place your drain pan underneath.
  3. Drain the Oil
    • Use a socket wrench to loosen and remove the drain plug.
    • Allow the oil to completely drain into the pan. Tilt the bike slightly if needed to ensure full drainage.
  4. Replace the Drain Plug
    • Wipe down the plug and threads. Reinstall it, tightening until snug, but do not over-tighten.
  5. Refill With Fresh Oil
    • Locate the oil fill cap (left side of the engine, often with a dipstick attached).
    • Using your funnel, pour 650ml (0.65L) of Yamaha-recommended transmission oil into the fill port

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    • Lightly lubricate the dipstick o-ring with fresh oil for a good seal

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  6. Check Oil Level
    • Insert the dipstick without threading it in, remove and check the oil level. Add small amounts if necessary to reach the correct mark.
  7. Inspect for Leaks
    • Start the engine and let it idle for several minutes, then check around the drain bolt and fill port for any oil leaks

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    • If you see any signs of leaking, turn off the engine and address the source before riding.
  8. Dispose of Used Oil Properly
    • Take the used oil to a local recycling center or auto parts store. Do not dispose of oil in the trash or down drains.

Model-Specific Warnings and Best Practices

  • Clutch Slippage Alert:— The transmission oil also lubricates the clutch. Do not use oil with chemical additives or incorrect viscosity, as this can result in clutch slippage and transmission problems

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  • Auto-Oil Injection:— The 1999 PW80 is equipped with a factory oil-injection system. If yours is still installed, simply keep the under-seat tank filled with high-quality 2-stroke oil—do not premix unless your system has been removed and blocked off

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  • Drain Plug Gasket: Always check the condition of the drain plug washer or gasket, replacing it if damaged to prevent leaks.
  • Correct Oil Fill: Do not overfill. Too much oil can cause issues with shifting or excessive pressure inside the transmission case.
  • Maintenance Interval: Changing the transmission oil annually or every 20–30 hours of riding is a good standard for recreational use.

Conclusion

Changing the oil in your 1999 Yamaha PW80 is a beginner-friendly DIY task and a vital part of routine bike maintenance. Use only recommended oil and follow the steps carefully to maximize your PW80’s performance and longevity. Trust MotoSport.com for all your parts, fluids, and riding gear—ride safe and keep that Yamaha purring.

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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.