UNI MN-B5MS Rider Fuel Pg Air Filter MN/B5MS

( Brand: Uni ), ( Manufacturer Part Number: MN/B5MS ), ( Compatible Year: 1978 1977 ), ( Compatible Make: Harley Davidson ), ( Compatible Model: Fxs Low Rider ), ( Bundle Description: 1 Pc Genuine Uni Air Filters ), ( Type: Air Filters ), ( Core Charge: Free No Core Charge ), ( Fitment Type: Direct Replacement )

Review UNI Mn/b5ms Air Filter Harley Davidson Low Rider Fuel And Pg fits FXS 1977–1978

The **Uni MN/B5MS High-Flow Air Filter** is a meticulously engineered replacement designed to deliver superior performance and longevity for the 1977 1978 Harley-Davidson FXS Rider Fuel-injected models, ensuring optimal airflow while maintaining the integrity of your engine s breathing system. Crafted from high-quality, durable materials, this air filter features a robust **B5MS foam pre-filter** paired with a **MN (Medium Nitrile) main filter element**, a combination that balances filtration efficiency with minimal restriction. The pre-filter captures larger particles and debris, prolonging the life of the primary filter and reducing maintenance frequency, while the MN medium-grade material effectively traps fine dust, pollen, and road grime without compromising airflow. Engineered to fit seamlessly within the Rider Fuel s compact yet high-performance airbox, this filter maintains a tight seal to prevent bypass, ensuring clean air reaches the engine at all times critical for preserving cylinder and piston longevity while maximizing horsepower and throttle response. Its modular design allows for easy installation, requiring minimal tools and no modifications to the stock airbox, making it an ideal upgrade for both stock and modified bikes. Whether cruising on open highways or tackling dusty backroads, the Uni MN/B5MS air filter provides a reliable, high-performance solution that keeps your FXS Rider running smoothly while extending the life of your fuel-injected engine.

### Pros and Cons of Buying a Uni MN/B5MS Air Filter for a 1977-1978 Harley-Davidson FXS Rider Fuel-PG

The Uni MN/B5MS air filter is a popular aftermarket option for older Harley-Davidsons, including the 1977-1978 FXS with Fuel-PG injection. Here are the key advantages:

1. **Improved Airflow and Performance** The Uni filter is designed to provide better airflow compared to the stock paper element, which can help maintain or slightly enhance engine performance, especially in high-mileage or modified engines. The larger surface area and improved design reduce restriction, allowing more air into the combustion chamber.

2. **Durability and Longevity** Unlike some paper filters, the Uni MN/B5MS is made from a more robust material (often a cotton or synthetic blend) that can last longer before needing replacement. This is particularly useful for riders who travel frequently or modify their engines.

3. **Easier Maintenance** The filter can be cleaned and reused multiple times by washing it with mild soap and water, then drying it thoroughly. This reduces the frequency of replacements compared to disposable paper filters.

4. **Compatibility with Modifications** If you ve made modifications like a high-flow exhaust or performance camshaft, the Uni filter s improved airflow can help compensate for increased demand, preventing a vacuum leak or restriction that could hurt performance.

5. **Cost-Effective Over Time** While the initial purchase price is higher than a stock paper filter, the ability to clean and reuse it can save money in the long run, especially for riders who put high mileage on their bikes.

6. **Reduced Oil Consumption** Some riders report that the Uni filter helps reduce oil consumption in older engines, as it allows cleaner air to enter the combustion chamber without excessive restriction.

7. **Aftermarket Support and Availability** Uni filters are widely available through Harley parts suppliers, performance shops, and online retailers, making them easy to source and replace.

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1. **Higher Initial Cost** Compared to an OEM paper filter, the Uni filter is more expensive upfront. However, this is often offset by its longevity and reusability.

2. **Requires Regular Cleaning** Unlike a paper filter that you simply replace, the Uni filter needs to be cleaned after every few hundred miles (or as recommended by the manufacturer). Neglecting this can lead to clogging and reduced effectiveness.

3. **Potential for Oil Leaks** Some riders report that the Uni filter can sometimes leak oil if not properly seated or if the gasket is worn. This requires careful installation and occasional inspection of the filter housing.

4. **Not Ideal for Extreme Conditions** In extremely dusty or off-road environments, the Uni filter may not filter as effectively as a high-quality paper filter, though it still provides better protection than no filter at all.

5. **Mixed Reviews on Performance Gains** While some riders notice a slight improvement in throttle response or power, others report that the gains are minimal, especially on stock engines. The benefits are more noticeable in modified or high-mileage bikes.

6. **Installation Complexity** Replacing the filter requires removing the airbox and ensuring the new filter is properly seated and gasketed. Improper installation can lead to leaks or reduced performance.

7. **Compatibility with Fuel-PG Injection** The Fuel-PG injection system on your FXS is sensitive to airflow restrictions. While the Uni filter improves airflow, some riders with Fuel-PG report that excessive airflow can cause minor tuning issues, though these are usually minor and easily adjusted.

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The Uni MN/B5MS air filter is a solid choice for a 1977-1978 Harley-Davidson FXS with Fuel-PG injection if you prioritize durability, improved airflow, and long-term cost savings. It s particularly beneficial for riders who modify their bikes or put high mileage on them. However, it requires more maintenance than a paper filter and may not provide dramatic performance gains on a stock engine.

If you re looking for a balance between performance and ease of use, the Uni filter is a worthwhile upgrade. For riders who prefer simplicity and don t mind replacing filters more frequently, a high-quality aftermarket paper filter (like a K&N or a reputable OEM replacement) might be a more straightforward option.

- You want a long-lasting, reusable filter that reduces maintenance costs over time.

- You ve made modifications that benefit from improved airflow.

- You re willing to clean and inspect the filter regularly.

If you prefer a lower-maintenance solution or have concerns about potential oil leaks, consider a **high-quality paper filter** (such as a K&N or a genuine OEM replacement) as an alternative. Ultimately, the choice depends on your riding style, budget, and how much you value performance versus convenience.

Details:

Uni Air Filter for 1977-1978 Harley Davidson FXS Low Rider - Fuel pg: Status: In Stock.

part #: mnb5ms price

• $36.81

specifications intakefuelmotorcycle:

• for models: Fxs
• for makes: Harley, Davidson
• for years: 1977-1978
• brand: Uni
• mpn: Mn/b5ms
• compatible year: 1978 1977
• compatible make: Harley Davidson
• compatible model: Fxs Low Rider
• bundle description: 1 Pc Genuine Uni Air Filters
• type: Air Filters
• core charge: Free No Core Charge
• fitment type: Direct Replacement

general intakefuelmotorcycle:

• Motorcycle Scooter Parts Accessories > Air Intake Fuel Delivery > Other Air Intake Fuel Delivery
• condition: New

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• paid by: Seller
• policy: Returns Accepted
• time: 30 Days

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• class: Standard
• cost: $0.00
• service: Standard
• type: Fixed
• transit: 2-7 Days

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seller intakefuelmotorcycle:

• city: Multiple warehouses
• rating: 99.3%
• # reviews: 23030

offer intakefuelmotorcycle:

• sold: 0
• started: May 20, 2026
• quantity: 1
• availability: In Stock
• options: Ship-to-home

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