Air Filter Cleaning – Replacement Guide for 2020 Honda CRF450RX

Shop parts for a 2020 Honda CRF450RX Dirt Bike.

The 2020 Honda CRF450RX is engineered for serious off-road performance, and keeping the air filter clean – or replacing it when needed – is essential for peak engine health and power. Its OEM and aftermarket air filters use high-quality dual-layer foam to optimize airflow and filtration, letting your engine breathe freely whether racing or trail riding. Here is MotoSport's proprietary guide designed for this specific model:

When & Why To Clean or Replace

  • Inspect after every ride in dusty or sandy conditions. Light use may stretch cleaning intervals to every 2–3 rides.
  • Replace the filter immediately if damaged, torn, or losing shape.
  • Routine cleaning prevents dirt from restricting airflow, protecting performance and preventing costly engine damage.

Tools & Materials Needed

  • Replacement air filter (OEM or compatible high-performance foam)
  • Air filter cleaning solvent
  • Air filter oil
  • Clean rags or paper towels
  • Disposable gloves
  • 8mm socket or T-handle tool

Removal Procedure

  1. Unscrew and remove the seat using an 8mm socket or T-handle.
  2. Locate the airbox – the filter is secured with a fastener to the air cleaner housing.
  3. Mark the orientation for reinstallation. Loosen and gently pull out the air filter and cage assembly.

Cleaning Routine

  1. Remove filter from cage (if applicable).
  2. Rinse filter gently in cleaning solvent – avoid wringing, which can tear foam layers.
  3. Wash until all dirt and old oil are gone, then thoroughly dry.
  4. Apply air filter oil evenly across the foam layers. Massage oil in to ensure all pores are coated without pooling.
  5. Install filter back on the cage. Inspect for tears, seam splits, or thin spots. If damaged, replace with new.

Installation Steps

  1. Insert the filter assembly, aligning properly as marked.
  2. Tighten the filter fastener to exactly 1.8 foot-pounds for correct airbox seal.
  3. Reinstall seat – torque bolts to 19 foot-pounds.
  4. Double-check filter seal and seating at the airbox perimeter.

Special Notes for the 2020 CRF450RX Owner

  • This model's airbox is designed for easy access, but ensure no dirt falls into the intake during servicing. A clean rag can be stuffed into the intake opening before cleaning.
  • The dual-layer foam (rough outer, fine inner) must be fully oiled to trap all sizes of debris, a key feature of OEM and most high-performance filters.
  • Consider keeping a pre-oiled spare on hand for quick changes during multi-day events.
  • If upgrading to aftermarket filters, select ones with flame-laminated foam for durability and optimum airflow (compatible filters include Tusk, Twin Air, and K&N as tested for your specific bike).

MotoSport recommends checking your air filter before every ride – a clean and correctly mounted filter means more power, better throttle response, and reliable engine protection mile after mile. Always ensure the sealing ring seats flat and evenly for a dust-tight fit.

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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.