How to Change the Oil in a 2021 Honda CRF450RX: Step-by-Step Guide

Shop parts for a 2021 Honda CRF450RX Dirt Bike.

Proper oil maintenance is vital for the performance and longevity of your 2021 Honda CRF450RX. This guide, proprietary to MotoSport.com, covers all the tools and steps you need, while highlighting specific call-outs for this model so you can ride with confidence.

Tools and Supplies Needed

  • 8mm socket
  • 10mm socket
  • 10mm Allen key/Allen bit
  • Ratchet
  • Torque wrench
  • Drain pan
  • Honda oil filter (see owner's manual for part number)
  • Honda 20W-50 4-stroke engine oil (or manufacturer-approved equivalent)
  • New crush washer
  • New O-rings if required
  • Rags/shop towels
  • Gloves and safety glasses
  • Measuring cup or funnel
  • Contact cleaner (optional)

Specific Call-outs for the 2021 Honda CRF450RX

  • The oil drain bolt uses a 10mm Allen and is located in the same spot as other recent CRF450 models, under the bike, protected by the skid plate.
  • These bolts are often over-tightened; use care when loosening the drain bolt to avoid stripping the threads or damaging the case. Use a torque wrench when reinstalling.
  • The skid plate must be removed for access. The OEM plate uses two collared bolts. If you have an aftermarket skid plate, removal may differ.
  • Honda recommends changing oil and the filter every 15 hours of use, or after six races, whichever comes first.
  • Always reference the model-specific service manual for torque specs and additional details.

Step-by-Step: Changing the Oil

  • Warm up the Engine
    • Start the engine and let it idle for about one minute to warm up the oil. This helps the oil drain completely and suspends contaminants.
  • Remove Skid Plate
    • Use the 8mm or 10mm socket to remove the skid plate bolts. Set the plate aside.
      Note: Aftermarket skid plates may require different tools or more bolts for removal.
  • Remove Filler Cap
    • Remove the oil filler cap to allow air in, which enables the oil to drain more completely.
  • Place Drain Pan
    • Position the drain pan under the drain bolt.
  • Remove the Drain Bolt
    • Use the 10mm Allen key to remove the drain plug (located at the bottom of the crankcase, under where the skid plate was).
    • Be careful: Many riders find this bolt extremely tight. Use steady, controlled force and ensure the Allen key is seated firmly to avoid stripping.
    • Remove the old crush washer; replace with a new one during reinstallation.
  • Drain the Oil
    • Allow all the oil to fully drain out. This may take several minutes, especially if the engine isn't fully warm.
  • Replace the Oil Filter
    • Remove the left-side engine guard (held with an 8mm socket if stock guard).
    • Remove the oil filter cover and the old oil filter.
    • Install the new Honda oil filter and replace the cover, ensuring the O-ring is in good condition or replaced as necessary.
    • Tighten the cover bolts to factory torque specification, typically around 9 ft-lbs.
  • Reinstall the Drain Bolt
    • Install a new crush washer and reinstall the oil drain bolt by hand first, then torque it to spec per your manual. Do not over-tighten.
  • Add New Oil
    • Pour in the correct amount and type of oil (refer to owner's manual, but for most 2021 CRF450RX, around 1 quart/950ml when changing both oil and filter).
    • Use a funnel or measuring cup to avoid spills.
  • Check Oil Level
    • Check the oil level using the sight glass below the filler cap on the crankcase. Top off if needed.
    • Replace the oil filler cap.
  • Reinstall Skid Plate and Clean Up
    • Reattach the skid plate and any guards.
    • Ensure no tools or rags are left around the bike, and wipe any spilled oil from surfaces.
  • Safety and Final Check
    • Start the engine and let it idle for a minute, then turn off and re-check oil level. Top off if necessary.
    • Inspect the drain plug and filter area for leaks.

Pro Tips for CRF450RX Oil Changes

  • Never overtighten the drain bolt or filter cover;– this is a common mistake and can result in expensive repairs.
  • Dispose of used oil responsibly at your local recycling center or auto parts store.
  • Keep a log of each oil and filter change to track usage and maintenance intervals.

Changing your 2021 Honda CRF450RX oil is straightforward with the right tools and care. Consistent maintenance gives you the best performance on the track or trail—brought to you exclusively by 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.