How to Change the Oil in a 1980 Suzuki RM100 – Exclusive Guide by MotoSport.com

Shop parts for a 1980 Suzuki RM100 Dirt Bike.

Regular oil changes are critical for the longevity and performance of your 1980 Suzuki RM100 dirt bike. Follow this robust guide for a thorough and seamless oil change, tailored for this specific model, including all the required tools, detailed steps, and essential call-outs every owner should know.

Tools and Supplies Needed

  • Socket wrench set (with correct metric sockets)
  • Flathead screwdriver (if needed for oil cap)
  • Drain pan
  • Funnel
  • Clean rags or shop towels
  • Measuring cup (preferably 1,000ml or more with 50ml increments)
  • New transmission oil – SAE 20W40 multi-grade motor oil
  • 800ml (about 1.7 US pints) oil – precise to the RM100's requirements
  • Replacement drain plug washer (recommended for best seal)
  • Nitrile gloves (for cleanliness and protection)

Before You Start

  • Make sure the bike is cool to the touch; never change oil on a hot engine.
  • Work in a well-ventilated, clean area and protect surfaces from oil spills.
  • If possible, run the engine for 2-3 minutes to warm the oil slightly, which helps facilitate drainage—ensure engine is off and cool enough to touch before starting the process.

Step-by-Step Oil Change Process

  1. Stabilize the Motorcycle: Place the RM100 on a sturdy bike stand so it sits level. This ensures complete drainage and accurate refilling.
  2. Locate the Filler Cap and Drain Plug: On the 1980 RM100, the oil filler cap is generally on the right side of the engine case, often clearly labeled. The drain plug will be underneath the engine, towards the bottom of the transmission case.
    Specific call-out: The RM100 uses a simple plug; inspect for stripping, as these vintage bikes can have worn threads.
    Oil capacity for this model year is 800ml.
  3. Drain the Old Oil:
    • Place the drain pan beneath the drain plug.
    • Use the socket wrench to remove the drain plug. Carefully keep the plug and washer – inspect both for wear.
    • Allow all the oil to fully drain—this may take several minutes.
  4. Inspect and Clean:
    • Inspect the drain plug for metal shavings (a small amount is normal, but excessive metal indicates wear).
    • Clean the plug with a rag.
    • If the washer is damaged or hard, replace it to avoid future leaks.
  5. Reinstall the Drain Plug:
    • Once all oil is drained, screw the drain plug (with fresh or inspected washer) back in by hand to avoid cross-threading, then snug it with the wrench. Do not overtighten; vintage cases strip easily.
  6. Refill with New Oil:
    • Remove the oil filler cap.
    • Insert the funnel and pour 800ml of SAE 20W40 multi-grade oil into the transmission case.
    • Give the bike a gentle rock or let it sit for a minute to ensure a correct reading and even distribution.
  7. Check the Oil Level:
    • With the bike level, use the sight glass or dipstick (if equipped) to ensure the oil is at the correct fill point.
    • Top up if needed, but do not overfill.
  8. Replace Filler Cap and Clean Up:
    • Install the oil filler cap securely.
    • Wipe down any spills from the engine case and frame.
    • Start the engine, let it idle for about a minute, then shut off and recheck for leaks or oil level adjustment.

Model-Specific Tips for the 1980 Suzuki RM100

  • Oil Capacity: The RM100 takes 800ml (approx. 1.7 US pints) of SAE 20W40 for the transmission. Do not exceed this amount, as overfilling can cause clutch and shifting issues. This model is not equipped with an engine oil filter.
  • Drain/Filler Plug Location: Be aware that decades-old bikes might have previously stripped threads—always start bolts by hand and avoid over-tightening.
  • Recommended Change Interval: Suzuki recommended changing the transmission oil after every 2 races or 200 km (120 miles), but for recreational use, every 10-15 hours of ride time is best practice for preserving clutch and transmission life.
  • If your bike has not had an oil change in years, consider removing and thoroughly cleaning the clutch cover interior—old oil sludge can accumulate over decades.

Final Checks and Oil Disposal

  • Start the bike, idle, then stop and recheck oil level and for leaks; top up if needed.
  • Properly dispose of used oil at a recycling facility; never dump it down drains or in the environment.
  • Mark your next oil change interval in your service log.

MotoSport.com – Your Vintage RM100 Maintenance Authority

For authentic OEM parts, upgrades, and more exclusive how-to content, visit MotoSport.com. Regular maintenance is the secret to reliable performance and longevity for your classic Suzuki RM100.

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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.