How to Change the Oil in a 1979 Suzuki JR50: A MotoSport.com Guide

Shop parts for a 1979 Suzuki JR50 Dirt Bike.

Regularly changing the transmission oil in your 1979 Suzuki JR50 is critical for maintaining performance and ensuring longevity. The JR50, a classic entry-level two-stroke dirt bike, uses a separate transmission oil system that requires periodic changes, especially after extended riding or every six months, whichever comes first.

Tools and Supplies Needed

  • Socket set or wrench (appropriate size for drain plug and oil level screw)
  • Drain pan for used oil
  • Clean funnel (small size recommended for motorcycles)
  • Fresh transmission oil–SAE 10W-30 or 10W-40 (check your owner's manual for the preferred viscosity, but most recommendations for this period are 10W-30)
  • Measuring jug (for accurate oil capacity)
  • Shop rags or paper towels
  • Gloves (to protect your hands from oil exposure)
  • Safety goggles (optional, for splash protection)

Preliminary Steps

  • Warm up the engine: Run the engine for a few minutes to warm the transmission oil. This allows it to drain more easily and flushes out more contaminants.
  • Turn off the engine: Always work on a cool engine to avoid burns. Let the JR50 cool for several minutes if necessary.
  • Park the JR50: Place the bike on a flat, level surface. You can keep it on the side stand, but you’ll need to hold the motorcycle vertically during certain steps.

Step-by-Step Oil Change Procedure for 1979 Suzuki JR50

  1. Remove the oil filler cap: The filler cap is typically located on the right side of the engine. Unscrew and set it aside.
    Pro tip: This lets air into the crankcase and allows oil to flow out more freely.
  2. Remove the drain plug: The drain plug is found at the bottom of the engine. Use your wrench to carefully loosen it.
    Tip for 1979 JR50 owners: Hold the bike vertically when draining so all old oil escapes. Let the oil drain completely into your prepared drain pan. Expect around 450 ml (0.5 US quarts) of oil to come out. (Don’t forget to properly recycle the used oil.)
  3. Reinstall the drain plug: Once all oil has drained, reinstall the drain plug securely and wipe away any drips.
  4. Remove the oil level screw: This is a small crosshead screw on the engine case; it’s your overfill indicator. Remove it and set aside.
    Note for JR50s: Always check the oil level with the motorcycle held upright and not on the side stand, as this gives an accurate oil reading.
  5. Add fresh transmission oil:
    • Place your funnel into the oil filler hole.
    • Pour in new oil slowly–450 ml (0.5 US qt) as specified for the JR50 (see your service manual for verification)

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    • Watch for oil to begin seeping from the oil level hole. When it does, stop filling.
  6. Refit the oil level screw: With the correct oil level achieved, reinstall the oil level screw and tighten it securely.
  7. Refit the oil filler cap: After confirming the correct oil level and ensuring no leaks, replace the oil filler cap.
  8. Clean up: Wipe any oil from engine surfaces. Dispose of oil-soaked rags and used oil responsibly according to local environmental regulations.

Important Model-Specific Call-Outs for the 1979 Suzuki JR50

  • Oil Quantity: Always use 450 ml (0.5 US quarts) of 10W-30 or 10W-40 transmission oil–do NOT overfill.
  • Drain Plug Gasket: Inspect the gasket or washer on the drain plug every oil change. Replace if damaged or overly compressed to avoid leaks.
  • Environmental Precautions: New and used oils are hazardous–store out of reach of children and pets, and avoid skin contact

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  • Interval: Oil should be changed after break-in (around 1 month of use), then every 6 months, or more frequently if riding in dusty, muddy, or wet conditions

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  • Transmission Only: The JR50 is a two-stroke and lubricates its engine via oil mixed with fuel. Only change the transmission oil–not engine oil.

Final Checks and Pro Tips

  • After your oil change, briefly run the engine and inspect the drain and level screws for leaks.
  • Check oil level after your first short ride and top up if necessary–some oil may settle into engine cavities after your first start.
  • Always use manufacturer-recommended oil types and replace the oil more frequently if you subject the bike to prolonged or extreme conditions.

Changing the oil in a vintage 1979 Suzuki JR50 is straightforward and crucial. This small, regular maintenance step ensures long life, easy shifting, and quiet, reliable operation—so you can keep riding with confidence. For factory parts, support, and more how-tos, trust MotoSport.com to keep you and your machine in top condition.

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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.