How to Change the Oil in a 2015 Beta 390 RS

Shop parts for a 2015 Beta 390 RS Dirt Bike!

The 2015 Beta 390 RS stands out for its dual oil compartments one for the engine, one for the transmission. Maintaining proper oil levels in both is vital for performance & longevity. Below is a proprietary MotoSport guide to changing the oil on your MMY dirt bike.

What Makes the 2015 Beta 390 RS Unique?

  • Dual oil compartments: Separate engine & transmission oils do not interchange.
  • Precise fill amounts: Overfilling or underfilling either side can cause mechanical issues.
  • Special checking procedure: Engine oil level is checked while running; transmission oil while off.

Tools & Parts Needed

  • Liqui Moly 10W-50 or manufacturer-spec oil
  • Replacement oil filter
  • Replacement o-rings (filter cover, filler caps, drain bolts)
  • Drain pans
  • 8 mm and 13 mm sockets
  • Torque wrench
  • Rags

Step-by-Step Guide for Oil Change

  1. Warm up engine for 2-3 minutes. This helps oil flow easier.
  2. Remove skid plate to access drain bolts.
  3. Place drain pans beneath engine & transmission drain bolts.
  4. Remove filter cover (2 x 8 mm bolts). Carefully detach filter & O-ring for improved drainage.
  5. Remove engine oil drain bolt (13 mm socket). Allow full drainage. Repeat for transmission oil drain bolt.
  6. Clean magnetic tips of drain bolts to remove any metal debris for gearbox longevity.
  7. Replace the oil filter:
    • Open end faces engine; solid end faces cover.
  8. Install new O-rings on filter cover & both drain bolts.
  9. Reinstall bolts with torque specs:
    • Engine drain bolt: 15 Nm–do not overtighten.
    • Transmission drain bolt: 20 Nm.
    • Filter cover: 10 Nm.
  10. Refill oils:
    • Engine: Add 750 ml Liqui Moly 10W-50.
    • Transmission: Add 750 ml Liqui Moly 10W-50.

    Tip: Ignore side glass and check bolts—trust the measured volume. Overfilling can occur if following old manual check plug advice.

  11. Replace filler caps, using new O-rings, and tighten.

Owner Notes for MMY Beta 390 RS

  • Never use the check bolts to verify oil level after refill—this often causes under- or overfilling.
  • The sight glass for engine oil is only accurate when engine is running at idle after refill and warm-up.
  • Both drain bolts are magnetic; inspect for abnormal metal debris each service.
  • Beta's oil system is unique—do not mix oil between engine and transmission compartments.
  • Always use new O-rings during an oil change; these inexpensive gaskets are critical against leaks.
  • Changing oil regularly improves clutch feel, shifts, and engine reliability in trail, enduro, or dual sport conditions.

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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.