How to Change the Oil in a 2021 Husqvarna FX350

Shop parts for a 2021 Husqvarna FX350 Dirt Bike.

Keeping your 2021 Husqvarna FX350 in top running condition means regular oil changes, essential for engine longevity – and peak performance. This model—closely related to the KTM 350 platform—features two drain bolts and is serviced in a specific way to prevent damage and ensure reliability. Below, you'll find a detailed, proprietary guide for MotoSport.com customers, including the necessary tools, step-by-step instructions, and key model-specific tips for your FX350.

Tools and Materials Needed

  • 8mm socket or Torx T30 bit – for removing skid plate bolts
  • 13mm socket – for main drain bolt
  • Oil drain pan
  • Rags or shop towels
  • Contact cleaner (optional, for tidying up any messes)
  • Measuring cup – to verify oil quantity
  • Torque wrench – to tighten bolts to spec
  • New engine oil (Motorex 4T Power Synth 10W-50, 1 liter recommended)
  • OEM oil filter (Part #77338005100)
  • Oil filter cover O-ring (Part #07703305178)
  • Strainer screen O-ring (Part #0770020170)
  • Lower drain plug O-ring (Part #0770110015)
  • Crush washer (Part #58038022000)

Step-by-Step Oil Change Process

  • Warm up the engine.
    Idle your FX350 for a few minutes. Warm oil flows better and removes more contaminants.
  • Remove the skid plate.
    Use an 8mm socket or T30 Torx bit to loosen the two bolts holding the skid plate. You don't have to remove it completely; just drop it down to access the drain plug and screens

    .
  • Position your drain pan under the engine.
    Make sure to capture all used oil.
  • Remove the two drain bolts.
    • First, the main drain plug (13mm bolt) at the bottom of the engine (has a magnetic tip that collects debris).
    • Second, the oil screen plug (found on the side of the case) – use a suitable socket or wrench.
    Allow all the oil to drain out completely

    .
  • Inspect and clean magnetic drain plug and oil screen.
    • Wipe the magnetic tip clean of any metal particles.
    • Remove the oil screen and rinse off any sludge or particles.
  • Replace the crush washer and O-rings.
    The FX350 uses specific O-rings and a crush washer that should be replaced at every oil change to prevent leaks

    .
  • Reinstall the oil screen, then the drain plugs.
    Tighten both to the correct torque specification (check the owner's manual, but generally around 10 Nm for the screen and about 20 Nm for the main drain bolt). Over-tightening can strip threads.
  • Replace the oil filter.
    • Remove the oil filter cover bolts on the right side of the engine (usually 8mm or T30).
    • Take out the old filter and any O-rings that come out with it.
    • Clean the filter housing with a rag.
    • Insert the new filter and O-ring, then reattach the cover, tightening the bolts by hand first and then to torque spec (typically 7.4 Nm as per the manual, which is just snug plus a little extra)

      .
  • Fill with fresh oil.
    • Open the oil fill cap on the left side of the cylinder head.
    • Pour in 1 liter (or specified amount in the manual) of Motorex 10W-50 full synthetic 4T oil

      .
    • Let the oil settle, then check the sight glass with the bike upright — adjust level if needed.
  • Run the engine and re-check oil level.
    Start the bike for a minute, shut it off, let oil settle, then verify it's between the marks in the sight glass.
  • Reinstall the skid plate and clean up.
    Secure the skid plate, wipe any spilled oil, and dispose of old oil/environmental waste at a recycling center.

FX350-Specific Tips and Call-Outs

  • Always use a new crush washer and O-rings to prevent leaks—these are inexpensive but important for sealing on this engine

    .
  • Torque the drain and filter cover bolts carefully. Over-torquing can strip the magnesium cases, causing costly repairs

    .
  • Check for debris on the magnetic drain plug. A small amount is normal, but large chips may indicate an internal issue.
  • Check your owner's manual for precise oil capacity and torque values for your 2021 model, as there are minor differences year to year

    .
  • Change oil every 10-15 hours of riding or after every race for maximum engine lifespan.
  • The 2021 FX350 shares most lubrication parts (and process) with 2017-2024 Husqvarna 350 models and KTM 350s

    .

Disclaimer

This proprietary MotoSport.com guide outlines the latest and most supported method for changing your 2021 Husqvarna FX350 oil. If in doubt, always refer to your official service manual or contact a certified dealer before proceeding. Proper disposal of used oil and materials is the responsibility of the owner.

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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.