How to Change the Oil in a 1998 Yamaha RT100: Step-by-Step Guide

Shop parts for a 1998 Yamaha RT100 Dirt Bike.

Changing the oil in your 1998 Yamaha RT100 is essential for maintaining smooth engine operation and longevity. This guide is proprietary to MotoSport.com and provides a robust, detailed walkthrough tailored specifically to this model so you can confidently take care of your RT100–s maintenance.

Tools and Supplies Needed

  • Socket wrench set
  • 17mm drain bolt socket or wrench
  • Drain pan
  • Funnel
  • Clean rags
  • New transmission oil (Recommended: SAE 10W-30 or 10W-40 motor oil; check your owner–s manual for specific recommendations)
  • Measuring cup (to ensure correct oil volume)
  • Gloves (optional, for cleaner work)

Oil Quantity and Type for 1998 Yamaha RT100

  • Total capacity: 0.7 L
  • Periodic oil change amount: 0.65 L
  • Recommended oil: See owner–s manual. Typical: SAE 10W-30 or 10W-40.

Step-by-Step Instructions

  • Warm Up Your Bike
    Start and run your RT100 for a few minutes. Warm oil drains faster and more completely, taking contaminants with it. Then, turn off the engine and let it cool slightly so you don’t burn yourself during the process.
  • Locate the Drain Plug and Oil Filler Cap
    The RT100–s drain plug is on the bottom of the engine case. The oil filler cap and dipstick are on the engine’s right side. Place your drain pan directly beneath the drain bolt.
  • Remove the Dipstick and Drain Plug
    Remove the dipstick (it unscrews from the filler hole on the right side of the case—rest it on the hole’s threads as a reference). Loosen and remove the drain plug with your socket wrench.
    Allow all the old oil to drain completely into your pan.
  • Inspect and Clean
    Inspect the drain plug for metal shavings or debris and wipe it clean with a rag. This is important to monitor engine health.
  • Reinstall the Drain Plug
    Reinstall the drain bolt and hand–tighten it, then torque it to spec (consult your owner’s manual or use gentle pressure if no torque wrench is available). Do not over–tighten, as this can strip the threads.
  • Add Fresh Oil
    Insert the funnel into the filler hole, and pour in 0.65 liters of new oil (or up to the “maximum” mark on the dipstick after a routine change).
    Use a measuring cup to ensure accuracy. Over–filling can cause leaks or engine issues; under–filling can lead to engine damage.
  • Check the Oil Level
    Wait a minute for the oil to settle, clean the dipstick, insert it (do not screw it in fully), and check the level. The oil should be between the “minimum” and “maximum” marks. Add small amounts of oil if needed to reach the correct level.
  • Reinstall the Dipstick and Clean Up
    Screw in the dipstick. Wipe off any spilled oil. Make sure all tools and rags are cleared away.
  • Start the Engine and Check for Leaks
    Run the engine for one minute, then shut it off and recheck for leaks at the drain bolt and oil filler area. Adjust oil level if necessary.
  • Dispose of Used Oil
    Take the used oil to a proper recycling facility or auto parts store that accepts used oil.

Specific RT100 Call-Outs and Tips

  • The 1998 Yamaha RT100 has a low total oil capacity; never exceed recommended fill as overfilling risks excessive crankcase pressure or leaks.
  • Always use the dipstick to check oil after letting the bike sit for a minute, as oil settles and gives a true reading.
  • The dipstick should be inserted but not screwed in when checking the level (rest it on the filler hole threads to get an accurate measurement on this model).
  • Avoid getting dirt into the engine when the filler cap is open—clean the area before opening.
  • If you do not have the original service manual, consider obtaining one for detailed diagrams, part numbers, and torque specs.

When to Change Oil

  • Change the oil every 10–15 riding hours, or at least every season, more often if you ride in dusty or harsh conditions.
  • Always perform an oil change as part of the pre-season check or before long storage periods.

Final Checklist

  • Correct oil type and quantity used
  • Drain plug and dipstick properly tightened
  • No leaks after change
  • Old oil properly disposed of

Performing regular oil changes is a simple but crucial way to keep your 1998 Yamaha RT100 running at its best. For additional parts, oil, and model-specific maintenance tips, visit MotoSport.com for trusted dirt bike support and products.

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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.