Air Filter Cleaning – Replacement Guide for 2018 Honda CRF125F

Shop parts for a 2018 Honda CRF125F Dirt Bike.

Routine maintenance of your 2018 Honda CRF125F air filter is critical for engine performance and durability. Proper air filter care boosts engine longevity, ensures reliable throttle response, and protects sensitive internal components from contaminants found on the trail. This MotoSport guide covers air filter removal, cleaning, inspection, and replacement — customized for the CRF125F.

Tools & Supplies Needed

  • Socket wrench (to remove air box cover bolts)
  • Mild detergent or foam filter cleaner
  • Bucket or basin
  • Clean water
  • Foam filter oil
  • Gloves (optional for handling oily filter and debris)
  • Clean lint-free towels

Step-by-Step Air Filter Removal

  • Locate the air filter housing under the seat. Remove the seat if needed.
  • Use a socket wrench to remove the bolts securing the air box cover. Set bolts aside safely.
  • Lift off the cover – expose the foam air filter.
  • Carefully pull out the air filter. Inspect the sealing surface and rim for excess dirt. Clean these areas thoroughly before filter reinstallation to ensure a proper seal.

Cleaning Instructions

  • Remove loose dirt by tapping the filter gently.
  • Immerse the foam filter in a bucket with warm water and mild detergent or designated filter cleaner. Gently squeeze (do not twist or wring aggressively) to release debris and oil.
  • Rinse the filter until water runs clear. Repeat if necessary.
  • Squeeze out excess moisture. Allow the filter to air-dry completely before oiling.

Oiling – Inspection

  • Apply high-quality foam filter oil evenly. Work oil through the foam for complete coverage without dripping.
  • Inspect the foam for tears, breakdown, or excessive wear. If any damage or persistent staining remains, replace the filter.

Reinstallation

  • Clean the air box rim and sealing surfaces thoroughly. Honda designed the CRF125F air box for easy access – take advantage and wipe away all residue and crankcase blow-by before sealing.
  • Reinsert the dried and oiled filter. Ensure a snug fit to avoid any bypass of dust or dirt.
  • Refit the cover and bolts, reinstall the seat.

Special Notes for the 2018 Honda CRF125F Owner

  • The CRF125F features a straightforward foam filter design. Cleaning the air box rim is essential for this model – minor debris around the seal may allow engine contaminants.
  • Inspect for crankcase breather seepage in the air box. Wipe any oily residue, as this is a known occurrence on this model – keeping this area clean minimizes dust stick and maximizes filter seal.
  • Replace the filter immediately if you notice tears, degraded foam, or excess blow-by. Not doing so risks engine damage.
  • Consider keeping an extra air filter on hand for extended trail days, dusty races, or rides under severe conditions.

How Often to Clean or Replace

  • After every extended or dusty ride
  • If any sign of engine performance loss or excess particulate bypass is noticed
  • At least every 8–10 riding hours in moderate conditions; inspect after every ride if trails are sandy or extremely dry

Keep your 2018 Honda CRF125F at peak performance – clean and oil your air filter regularly, inspect the air box rim and sealing surface, and rely on MotoSport for all genuine parts and expert advice.

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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.