Air Filter Cleaning & Replacement Guide for 1999 Cobra CM50

Shop parts for a 1999 Cobra CM50 Dirt Bike.

The 1999 Cobra CM50 is a competitive mini motocross machine, known for its lightweight frame, liquid-cooled 49.8cc 2-stroke engine, and unique air filtration system designed to keep out dust and dirt during aggressive off-road riding. Proper air filter maintenance is vital to maximize performance and engine longevity on this model. This guide from MotoSport covers step-by-step cleaning and replacement instructions, details unique to the CM50, and crucial best practices for owners.

Unique Air Filter Features in the 1999 Cobra CM50

  • Special Designed Sock Filter: The CM50 utilizes a specially designed sock-style foam air filter, critical for trapping fine particles and protecting your carburetor and engine internals.
  • Dual-Stage Foam: The OEM filter is crafted from dual-stage reticulated foam, offering enhanced filtration by capturing both large and microscopic debris.
  • Light-Colored Foam: The light color makes it easier to see if filter oil is evenly applied, avoiding inconsistencies that can impact engine tuning.

How Often to Clean or Replace the Air Filter

  • Clean and re-oil after every moto or ride, especially in dusty or muddy conditions.
  • Carry three filters one for practice, one for the first race, one for the second for uninterrupted performance.
  • Replace the filter if it shows signs of tearing, degradation, or excessive clogging that cannot be cleaned.

Cleaning Instructions for Your 1999 Cobra CM50 Air Filter

  1. Remove the Filter: Loosen the air box retaining clip and pull out the foam filter with care. Check for tears or holes.
  2. Pre-Clean: Gently tap to dislodge loose dirt. Avoid compressing debris deeper into the foam.
  3. Wash: Submerge in a container with a mild solution of warm water and a dedicated air filter cleaner or low-residue soap. Gently massage but do not wring or stretch the filter.
  4. Rinse: Rinse with clean water until no soap or dirt remains. Squeeze out excess water carefully.
  5. Dry: Allow to air dry completely away from direct heat or sun, which may damage the foam.
  6. Oil: Once dry, apply a high-quality, water-resistant foam air filter oil until the entire filter is coated but not dripping. Uneven oiling can change your carburetor jetting and reduce performance.
  7. Inspect: Ensure there are no uncoated sections and the glue seams are intact.
  8. Reinstall: Carefully refit the filter, ensuring it does not contact the frame, especially in wet conditions, to avoid bypassing the filtration system.
  9. Wipe the airbox: Remove dirt from the airbox and check for signs of water or debris before reinstalling the filter.

Replacement Instructions

  • Remove old filter as above.
  • Select a CM50-compatible dual-stage foam filter (OEM size is recommended for best fit and filtration). CM50 filters are handmade for quality. Check for fitment specific to 1999 models.
  • Pre-oil the new filter thoroughly before installation.

Essential Maintenance Tips for 1999 Cobra CM50 Owners

  • Never use gas or harsh solventsthese can break down the foam and glue seams, shortening filter life.
  • Avoid racing fuels: 93 octane pump gas is recommended in this model.
  • Use special carburetor plug (carb condom) when washing or storing the bike to prevent water entry.
  • Routinely check for proper seal at mounting surface to avoid unfiltered air bypass.

Proprietary MotoSport Recommendation

The air filtration system on your 1999 Cobra CM50 is designed for extreme conditions—but only if cleaned and oiled properly after every ride. Changing or cleaning the filter is quick insurance for the high-revving engine. MotoSport recommends every rider keep at least three pre-oiled air filters on hand per race day, and use only water-resistant foam filter oil for best carburation and protection.

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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.