How to Change the Oil in a 1994 Yamaha RT100

Shop parts for a 1994 Yamaha RT100 Dirt Bike.

The 1994 Yamaha RT100 is a classic two-stroke dirt bike, and regular oil changes are crucial to keep it running smoothly. Unlike four-stroke engines, the oil in a two-stroke like the RT100 primarily lubricates the transmission and clutch. Here’s a comprehensive, step-by-step guide exclusive to MotoSport.com, covering all you need to know: tools, steps, and model-specific insights for changing the transmission oil on your RT100.

Tools and Supplies Needed

  • Socket set and/or wrench set (for drain and filler bolts)
  • Flat-head screwdriver (helpful for loosening stubborn bolts)
  • Measuring cup (for correct oil volume)
  • Clean funnel
  • Drain pan (to catch used oil)
  • Rags or shop towels
  • New transmission oil: SAE 15W-40 or equivalent as specified for the 1994 RT100
  • Gloves (optional, for cleanliness)
  • Parts cleaner/degreaser (optional, for cleaning any spills)

Preparation Steps

  • Warm up the engine for a few minutes by running it at idle–this helps thin out the oil, making it easier to drain.
  • Turn off the engine and ensure the bike is securely positioned on a stable stand.
  • If applicable, clean around the drain bolt area to prevent dirt from contaminating the transmission.

Step-by-Step Oil Change Procedure

  1. Locate the Drain and Fill Bolts
    • The drain bolt is usually found on the bottom of the crankcase, near the lowest point. The fill bolt/cap is often located on the right side of the engine casing.
  2. Drain the Old Oil
    • Place the drain pan directly under the drain bolt.
    • Remove the drain bolt carefully using the appropriate socket. Be cautious, as the oil may be hot.
    • Allow all oil to drain completely. Tilting the bike slightly can help remove residual oil.
    • Inspect the condition of the old oil–a milky color could indicate contamination.
    • After draining, inspect and clean the drain bolt. If the bolt has a crush washer, check its condition and replace if necessary.
  3. Reinstall the Drain Bolt
    • Replace and hand-tighten the drain bolt. Then, use your wrench to snug it up. Do not overtighten; refer to the service manual for the proper torque setting if available.
  4. Add New Oil
    • Remove the transmission oil fill bolt/cap.
    • Insert a clean funnel into the fill hole.
    • Pour the specified amount of SAE 15W-40 oil into the transmission. The correct capacity for the RT100 is generally around 650ml (0.69 US qt), but always check your owner’s manual or pre-marked measurement for confirmation

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    • After filling, replace the oil cap securely.
  5. Check Oil Level
    • Some RT100 models have a sight glass or dipstick to verify oil level. If so, place the bike upright (not on the side stand) and check that the oil reaches the appropriate gradient

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    • Avoid overfilling, as this can cause foaming or leaks.
  6. Clean Up
    • Wipe down any spilled oil from the engine and surrounding parts.
    • Dispose of the used oil properly at a local recycling center or auto parts store.
  7. Final Inspection
    • Start the engine and let it idle for a few minutes.
    • Check for leaks around the drain bolt and oil fill cap.
    • Re-check the oil level and top up if necessary.

Model-Specific Call-Outs for the 1994 Yamaha RT100

  • Oil Type: Use SAE 15W-40 for the transmission/crankcase, not engine oil, since the RT100 is a two-stroke and uses a separate premix for engine lubrication

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  • Oil Volume: Ensure you use the correct volume–650ml is common, but consult the bike’s owner’s manual for exact figures to avoid under- or overfilling

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  • Oil Change Interval: For optimal clutch and gearbox performance, change the oil after every 10–15 hours of riding or after any particularly muddy or wet rides.
  • Inspect Seals: Take this opportunity to inspect the drain plug’s sealing washer and replace if worn, as leaks can cause catastrophic transmission failure.
  • Transmission Use: Remember, on two-strokes like the RT100, the oil’s main purpose is to lubricate the transmission and clutch, so skipping changes can lead to hard shifting, clutch problems, and early wear

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  • No Oil Filter: The RT100 does not have a separate oil filter for the gearbox oil. Keeping the oil cleaned and changed regularly is the best way to protect internal parts.

Conclusion

Changing the oil in a 1994 Yamaha RT100 is simple yet critical maintenance. With a few basic tools, high-quality oil, and these steps, you’ll keep your bike shifting smoothly and extend its service life. For premium lubricants, parts, and gear, always check MotoSport.com to keep your Yamaha riding at its best.

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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.