Introduction
The Uni Filter NU-4119ST is a 2-stage foam air filter designed to provide superior engine protection for ATVs and other powersports vehicles. Its unique open-cell polyurethane foam, when wetted with specialized filter oil, effectively traps dirt, dust, and mud, ensuring clean air intake even in severe operating conditions. This manual provides essential information for the proper installation, operation, and maintenance of your Uni Filter.
Product Overview
The Uni Filter NU-4119ST features a dual-stage filtration system for enhanced performance and extended engine life. Key characteristics include:
- 2-Stage Filtration: Increases performance and engine life by effectively capturing particles of varying sizes.
- Dual Filters: Designed to trap dirt and keep motors running clean, even under the most severe conditions.
- Vehicle Specific Fit: Engineered for precise fitment in compatible vehicles.
- Product Type: Engine Air Filter.
Image: The Uni Filter NU-4119ST, a red foam air filter with a metal clamp at the base, designed for powersports vehicles.
Compatibility and Fitment
This air filter is designed for vehicle-specific applications. It is important to verify compatibility with your vehicle's make and model before installation. The Uni Filter NU-4119ST is known to fit models such as the 2004 Honda Foreman 450, 1997 Honda Foreman 400, and 2004 Honda Fourtrax 350. However, it is not compatible with the TRX400EX or 450R models, despite appearing in some search results.
Always consult your vehicle's service manual for specific air filter requirements and dimensions to ensure proper fitment.
Setup and Installation
- Preparation: Ensure the engine is off and cool. Gather necessary tools, which may include screwdrivers or wrenches depending on your vehicle's airbox design.
- Access Airbox: Locate and open your vehicle's airbox. Remove the old air filter.
- Inspect OEM Cage: For this specific Uni Filter model (NU-4119ST), it is critical to use the original equipment manufacturer (OEM) internal filter cage/baffle. The Uni Filter is designed to fit over this cage. Failure to use the OEM cage will result in the filter collapsing and improper filtration.
- Oil the Filter: Apply a specialized foam air filter oil evenly to the Uni Filter. Knead the filter to distribute the oil thoroughly. The filter should be saturated but not dripping. This oil is essential for trapping fine dust particles.
- Install Filter: Carefully slide the oiled Uni Filter onto the OEM internal filter cage. Ensure it is seated correctly and securely.
- Reassemble Airbox: Close and secure the airbox cover. Double-check all connections to ensure no air can bypass the filter.
Note: Always refer to your vehicle's specific service manual for detailed instructions on air filter replacement, as procedures may vary.
Operating Principles
The Uni Filter NU-4119ST operates on a simple yet effective principle. The open-cell polyurethane foam, when treated with filter oil, creates a sticky, porous barrier. Air passes through the foam, and airborne contaminants (dirt, dust, sand) adhere to the oiled foam. The 2-stage design means there are two layers of foam, typically with different pore sizes, to capture a wider range of particle sizes, providing enhanced protection for your engine's internal components.
Maintenance
Regular maintenance of your Uni Filter is crucial for optimal engine performance and longevity. The frequency of cleaning and re-oiling depends on riding conditions and usage.
Cleaning Procedure:
- Remove Filter: Carefully remove the Uni Filter from the airbox.
- Pre-Clean: Gently tap the filter to remove loose dirt and debris.
- Wash: Use a specialized foam air filter cleaner or a mild detergent with warm water. Work the cleaner into the foam, gently squeezing (do not twist or wring) to dislodge dirt. Repeat until the filter is clean.
- Rinse: Rinse the filter thoroughly with clean water until all soap residue is gone.
- Dry: Allow the filter to air dry completely. Do not use heat (e.g., hairdryer, direct sunlight) as this can damage the foam.
Re-Oiling Procedure:
- Apply Oil: Once the filter is completely dry, apply a high-quality foam air filter oil. Distribute the oil evenly by gently kneading the filter.
- Check Saturation: The filter should be uniformly coated and appear slightly darker in color, but no oil should be dripping.
- Reinstall: Reinstall the freshly oiled filter following the "Setup and Installation" steps.
Warning: Using improper cleaning agents or oils can degrade the foam material and compromise filtration effectiveness.
Troubleshooting
| Issue | Possible Cause | Solution |
|---|---|---|
| Filter does not fit correctly or collapses | Incorrect vehicle application; OEM internal cage not used. | Verify filter compatibility with your vehicle. Ensure the OEM internal filter cage is installed before placing the Uni Filter. |
| Engine performance issues (e.g., rough idle, reduced power) | Dirty or improperly oiled filter; air leak around filter. | Clean and re-oil the filter. Check for proper seating and sealing of the filter and airbox. |
| Filter appears damaged or torn | Improper handling during installation/cleaning; prolonged use in harsh conditions. | Replace the filter immediately to prevent engine damage. Handle with care during maintenance. |
Specifications
- Model: NU-4119ST
- Brand: 4into1 (Manufactured by Uni Filter)
- Product Type: 2-Stage Foam Engine Air Filter
- Shape: Round
- Item Weight: Approximately 4.8 ounces
- Product Dimensions: Approximately 5.5 x 4.6 x 4.6 inches
- Fit Type: Vehicle Specific Fit
- OEM Part Number: NU-4119ST
- UPC: 804451041199
Warranty and Support
For specific warranty information or technical support regarding your Uni Filter NU-4119ST, please refer to the manufacturer's official website or contact their customer service directly. Always retain your proof of purchase for warranty claims.
Manufacturer: Uni Filter
Brand (Seller): 4into1 Store