How to Change the Oil in a 1979 Honda Z50 – MotoSport.com Exclusive Guide

Shop parts for a 1979 Honda Z50 Dirt Bike.

Changing the oil in your 1979 Honda Z50 is a straightforward, essential maintenance task that keeps your engine running smoothly and extends its life. While the core process is simple, there are important details specific to this vintage model that every owner should know. Below you'll find a proprietary, easy-to-follow guide covering tools required, step-by-step instructions, and critical call-outs for the '79 Z50.

Tools & Supplies Needed

  • 17mm socket or wrench (for oil drain plug)
  • Socket wrench
  • Oil drain pan
  • Funnel (recommended for refilling without spills)
  • Clean shop rags
  • Nitrile or latex gloves
  • Honda-recommended 10W-40 4-stroke engine oil
  • Measuring cup (optional, for accuracy; capacity: 600 ml/0.63 US qt)

Preparation

  • Start with the engine warm, not hot—run for about 3-5 minutes. This helps old oil flow out completely.
  • Place the motorcycle on a level surface and ensure it’s upright, using a stand if available.
  • Turn the engine off and let it sit for a minute to cool slightly, avoiding burns during draining.

Step-by-Step Instructions

  1. Locate Drain Plug
    The oil drain plug is located at the bottom of the engine, directly beneath the crankcase. Use your 17mm socket or wrench to access it.
  2. Place Drain Pan
    Slide your oil drain pan directly under the drain plug to catch the old oil.
  3. Loosen and Remove Drain Plug
    With gloves on, slowly loosen the 17mm drain plug. Remove the plug by hand, allowing the oil to fully drain into the pan. Be careful—used oil can be hot and dirty.
    • Tip: Let the oil drain for at least 5-10 minutes to ensure it's fully emptied.
  4. Inspect and Clean
    Check the drain plug for metal debris (a little is normal). Wipe the plug and threads with a clean rag. Inspect the crush washer/gasket for wear or damage, replacing it if needed.
  5. Reinstall Drain Plug
    Screw the cleaned drain plug back in by hand first, then snug it up with your wrench. Do not overtighten—it’s an aluminum case and can strip easily. Tighten to approximately 14 ft-lbs (19 Nm).
    • Specific Z50 Call-out: Overtightening can strip the case threads—a known issue on these small Honda engines.
      Use a torque wrench if possible and stop once firmly seated.
  6. Remove the Oil Filler Cap
    The oil filler cap (doubling as a dipstick) is located on the right side of the crankcase.
  7. Add New Oil
    Using a funnel, add the recommended 10W-40 oil. The correct amount for a 1979 Honda Z50 is 600 ml (0.63 quarts).
    • Tip: Pour a little at a time, then check the dipstick before fully filling. The level should be between the ‘Min’ and ‘Max’ marks on the dipstick.
    • Z50 Owners: The oil fill opening is small. Go slow to avoid bubbling or spills.
  8. Check Oil Level
    Insert the dipstick without screwing it in to check level. Add oil if needed until it reads correctly.
  9. Replace Filler Cap
    Hand-tighten until snug—don’t overtighten.
  10. Start and Inspect
    Start the engine and let it idle for 1 minute. Turn off and wait 1 minute, then check under the bike and around the drain plug for any leaks. Recheck oil level; top up if necessary.
  11. Dispose of Old Oil Responsibly
    Pour used oil into a sealable container and bring it to a recycling facility or auto shop that accepts oil waste.

Important Model-Specific Call-Outs

  • Aluminum Thread Caution: Early Honda Mini Trail models (like the '79 Z50) are prone to case damage if the drain bolt is overtightened. Always use proper torque and check for thread wear.
  • Drain Plug Size: The engine uses a 17mm drain plug common to most Z50 variants from 1970 through the 1990s. Later models are nearly identical in this aspect.
  • Oil Recommendation: Use only high-quality 10W-40 four-stroke engine oil. Some owners use synthetic for longer intervals, but classic Honda specs are for conventional oil—changing regularly is better than expensive oil infrequently.
  • Oil Capacity Confirmation: The exact fill is 600 ml. Overfilling can cause leaks or engine stress; underfilling will lead to accelerated wear.
    This is slightly less than later Z50s but consistent with all classic Honda minibikes of the era.

Additional Tips

  • Change oil every 1,000 miles or 6 months, whichever comes first, for a well-maintained engine.
  • For best draining, change oil after a short ride while the engine is warm.
  • Keep a log of oil changes—vintage bikes love regular attention.

Why Change Your Oil Regularly?

  • Fresh oil lubricates, cools, and helps seal the engine’s moving parts, preventing wear and improving overall reliability.
  • On vintage bikes like the 1979 Z50, fresh oil reduces the risk of sludge and stuck rings, especially if the bike sits for long periods.

Conclusion

Changing the oil on your 1979 Honda Z50 is relatively easy, even for a beginner. Handle the delicate aluminum threads with care and don’t skimp on oil quality. Proper, regular changes ensure your classic Honda Mini Trail stays on the road and riding like new for decades to come.

This guide is proprietary to MotoSport.com and tailored specifically for the 1979 Honda Z50. For more exclusive vintage bike maintenance tips, visit MotoSport.com.

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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.