Air Filter Cleaning & Replacement Guide for 2020 Honda CRF125FB

Shop parts for a 2020 Honda CRF125FB Dirt Bike.

The 2020 Honda CRF125FB Big Wheel is a dedicated off-road motorcycle built for reliability, featuring a robust 125cc air-cooled SOHC single-cylinder engine. For peak performance and maximum engine longevity, regular air filter maintenance is critical–especially if you ride in dusty, wet, or sandy environments. This guide will help you properly clean or replace the air filter on your CRF125FB and note key model specifics every owner should know.

Why Air Filter Care Is Critical

Maintaining a clean air filter is essential for the 2020 CRF125FB because:

  • A clogged or dirty air filter can cause poor throttle response, reduce engine power, and allow damaging dirt into the motor.
  • The stock filter is a high-efficiency, dual-stage foam unit specifically engineered to maximize airflow while trapping dust and debris, striking a balance critical for this model's air-cooled, off-road design.

How Often Should You Clean or Replace the Air Filter?

  • After every ride: Clean the air filter if you rode in extreme dust, sand, or mud.
  • Every 2–3 rides: Inspect and clean for general recreational use.
  • Replace the filter: If it is torn, degraded, or no longer seals to the air box properly. Stick to Honda OEM or proven aftermarket options for best results.

Tools & Materials Needed

  • New air filter (OEM or dual-stage foam)
  • Foam air filter cleaner & oil
  • Air box cover or clean rags
  • Philips screwdriver, socket wrench
  • Gloves

Step-by-Step: Cleaning or Replacing the Air Filter

  1. Remove the Seat:
    Use the appropriate tool to remove the seat bolts and slide the seat off to access the air box.
  2. Remove the Air Filter:
    Unscrew the wing nut or retainer holding the filter in place. Carefully remove the foam filter; avoid dropping dirt into the air box.
  3. Inspect the Filter:
    Look for tears, degradation, or loss of sealing surface. If damaged, replace the filter.
  4. Clean the Filter (if reusing):
    • Rinse the foam filter gently in a cleaning solution designed for foam filters.
    • Work the dirt out by hand, avoiding harsh wringing or stretching.
    • Rinse with clean water and let it fully dry.
  5. Apply Foam Filter Oil:
    • When dry, apply air filter oil, ensuring even coverage but no excess dripping. Work the oil thoroughly into the foam.
    • Pre-oiled filters are available for convenience and consistency.
  6. Reinstall the Filter:
    Fit the filter securely in the air box and ensure it seals completely around the edge. Install the retainer or wing nut.
  7. Clean Inside Air Box:
    Wipe the inside of the air box with a clean, damp rag, being careful not to let debris fall into the intake tract.
  8. Reinstall Seat:
    Refit the seat and tighten the bolts to specification.

Model-Specific Notes for the 2020 CRF125FB

  • This model is equipped with a dual-stage foam filter – the outer, coarse foam catches large particles, while the fine inner foam captures smaller contaminants.
  • Always check the air box drain tubes for oil or water accumulation before reinstalling the filter. If the drain tube overflows, the filter can be contaminated with engine oil, causing poor performance.
  • Be gentle when removing or installing the filter to avoid damaging the foam or its sealing surface.
  • The 2020 CRF125FB Big Wheel's increased ground clearance and suspension travel (compared to the standard version) make it popular for larger riders and rough terrain. Regular air filter maintenance is especially important to protect the air-cooled engine during high-exertion use.

Quick Tips

  • Have two air filters – always keep a clean, oiled spare ready for quick swaps during multi-day rides.
  • Use only foam filter oil (not standard motor oil).
  • If the filter is difficult to seal, check for air box warping or old gaskets and replace as needed.

Regular air filter service is one of the most effective ways to extend engine life and maintain your 2020 Honda CRF125FB's performance for years to come.

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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.