Ninja 400 Air Filter: Stock vs. Performance

The Kawasaki Ninja 400 has taken the lightweight motorcycle class by storm, capturing the hearts of enthusiasts and racers alike. Whether you're hitting the track or enjoying spirited road rides, optimising your machine for peak performance is often a priority. A common question that arises among owners looking to enhance their bike's capabilities, particularly when considering upgrades, is about the air filter: Does the Ninja 400 come with a pre-oiled air filter from the factory? The simple answer is no; the stock Ninja 400 is equipped with a thin paper air filter designed for general use and is typically disposable, requiring replacement rather than cleaning and re-oiling.

However, for those delving into performance modifications, such as the comprehensive Graves Motorsports Power Up Kit, the discussion shifts considerably. This kit, for instance, includes a DNA high-flow air filter, which is indeed pre-oiled and offers significant advantages over the standard OEM unit. Understanding the differences between these filters and their impact on your engine's breathing is crucial for any Ninja 400 owner aiming for superior performance.

Stock Air Filter vs. High-Flow Performance Filters

The standard air filter on the Kawasaki Ninja 400 is a paper element, designed to effectively filter incoming air while keeping manufacturing costs down. This filter is meant for periodic replacement as part of routine maintenance. It is not pre-oiled, nor is it intended to be cleaned and re-oiled for reuse. Its primary function is to protect the engine from contaminants, and it performs this task adequately for everyday riding conditions.

In contrast, high-flow performance air filters, such as the DNA filter provided in the Graves Motorsports Power Up Kit, are engineered for maximum airflow and improved filtration. These filters are typically made from cotton fibre, which, when oiled, provides excellent filtration properties while allowing a significantly greater volume of air to pass through to the engine. The DNA filter, for example, boasts a claimed 14.25 percent improvement in airflow, increasing from 164.70 CFM (Cubic Feet per Minute) to 188.20 CFM compared to the stock unit. A key advantage of these aftermarket filters is their reusability; they can be cleaned and re-oiled as needed, making them a more durable and cost-effective solution in the long run than disposable paper filters.

Why Upgrade Your Air Filter?

Upgrading your air filter is a fundamental step in optimising your motorcycle's engine. Here’s why it matters:

• Improved Engine Breathing: Just as a full exhaust system allows your engine to expel gases more efficiently, a high-flow air filter enables it to intake air more efficiently. This balance is vital for achieving an optimal air/fuel mixture.
• Enhanced Power and Torque: More efficient air intake directly translates to better combustion, leading to noticeable gains in horsepower and torque across the rev range. For the Ninja 400, this can contribute to significant performance boosts, especially when combined with other upgrades.
• Optimised Fueling: Performance air filters are often part of a larger tuning strategy. The new map provided by Graves, for instance, was specifically developed and tuned using their DNA filter. This ensures that the engine receives the correct air/fuel ratio, preventing issues like running too lean or too rich, which can be harmful to your engine and leave power on the table.
• Reusability and Durability: Unlike the disposable stock unit, performance filters are built to last. Their washable and re-oilable design means you save money on replacements over time and reduce waste.

The Graves Motorsports Power Up Kit: A Comprehensive Approach

The question of whether the Ninja 400 has a pre-oiled air filter often arises in the context of performance upgrades, particularly kits like the Graves Motorsports Power Up Kit. This kit is a prime example of a holistic approach to enhancing your Ninja 400's capabilities, especially for club racing or serious track use. It integrates several key components to unlock the bike's full potential.

At the heart of the kit is a beautifully crafted stainless-steel Graves Motorsports full-exhaust system, available with carbon or titanium silencers. This system alone offers significant weight savings – the titanium silencer version weighs a svelte eight pounds compared to the original exhaust and emissions components tipping the scales at 15.8 pounds, resulting in a 7.7-pound reduction. Beyond weight, a full exhaust system is one of the most cost-effective ways to liberate more power from your engine and ensure it runs optimally under demanding conditions.

Crucially, the Power Up Kit includes the pre-oiled DNA high-flow air filter, directly addressing the intake side of the engine's breathing equation. This filter is integral to the kit's design, as the accompanying fuel map from Graves Motorsports was meticulously developed on their dynos with this specific filter in place. This ensures seamless integration and maximum efficiency.

To tie it all together, the kit features a Flash Tune bike-side harness, allowing you to re-flash your 400’s ECU at will. Graves Motorsports also provides a pre-optimised fuel map tailored for their exhaust and the DNA filter. This eliminates the need for costly dyno runs or complex custom tuning for the average do-it-yourselfer. The result is a claimed 10 percent increase in power, taking the Ninja 400 from approximately 45 to 51 horsepower and maximum torque from 26 to 30 ft-lbs.

The kit also includes a smog block-off plate. Removing emissions components like the charcoal canister and air-induction system, along with using the block-off plate, ensures more consistent fueling. The Graves map is designed to eliminate related trouble codes from the ECU, allowing for these modifications without issue. This comprehensive approach ensures that every component works in harmony to deliver substantial gains in power, throttle response, and overall riding experience.

Air Filter Installation Overview

Accessing and replacing the air filter on your Ninja 400 is a task that every owner will likely encounter during routine maintenance or when performing upgrades. While not overly complex, it does require a few key steps:

1. Fuel Tank Removal: The most significant step is disconnecting and carefully removing the fuel tank. This involves disconnecting the fuel line (using the red 'quick-release' clip), the four-pin fuel pump connection, and removing the bolts securing the tank and seat pan. Extreme care must be taken to avoid damaging the fuel rail or line during this process. Once unbolted, the tank is held by two posts in rubber grommets; gently wiggling it aft will dislodge it.
2. Airbox Access: With the fuel tank safely removed, you gain access to the airbox. The airbox cover is secured by seven screws. Removing these allows you to lift the cover and expose the interior.
3. Filter Replacement: The stock filter is typically held in place by a single screw. Once this is removed, the old filter can be taken out and replaced with the new DNA high-flow filter.
4. Reassembly: The process is then reversed for reinstallation, ensuring all connections are secure and the fuel tank is properly seated.

It's important to remember that this is an overview of observations and tips, not a strict instructional guide. Always refer to the detailed instructions provided by Graves Motorsports and Flash Tune for precise steps and safety precautions. If you are not comfortable performing these modifications yourself, it is always advisable to seek assistance from a licensed professional technician.

Broader Performance Enhancements for the Ninja 400

Beyond the immediate benefits of a performance air filter and exhaust system, the Kawasaki Ninja 400 offers several other avenues for enhancement, especially for those seeking to refine its capabilities for track use or spirited road riding. While a brilliant machine out of the box, there's always room for improvement, particularly concerning its ergonomics and chassis components.

Ergonomics and Rider Comfort

One common observation among Ninja 400 owners relates to its ergonomics. The handlebars, for instance, are angled inward quite significantly. While there's ample clearance with the bodywork, some riders find this position somewhat restrictive, suggesting that wider, more open-angled aftermarket bars could greatly improve rider comfort and control. Similarly, the saddle offers limited room for movement, which can be noticeable during longer rides or aggressive body positioning on the track. The subframe appears to be welded, making modifications irreversible but not impossible for those prioritising more seat room or passenger/luggage capacity.

Furthermore, the foot pegs are positioned relatively high, creating a somewhat tight seat-to-peg ratio. While not the most uncomfortable setup, lower pegs could enhance comfort, especially for street riding or light touring, where a more relaxed rider triangle is often preferred over aggressive sportbike ergonomics.

Suspension and Handling

Manufacturers often economise on suspension components to keep motorcycle costs down, and the Ninja 400 is no exception. While the standard suspension performs well for its class, it does have limitations. For street riders, softening the high-speed compression could improve the bike's ability to absorb stutter bumps, leading to a smoother ride. For a dedicated track machine, full adjustability in the suspension would be a highly desirable upgrade, allowing riders to fine-tune damping and spring rates for optimal handling characteristics on a closed course.

Braking and Quickshifters

Braking performance is another area where enthusiasts often look for upgrades. While the stock brakes are adequate, more powerful or fade-resistant components could be beneficial for aggressive riding or track days. Lastly, the convenience of a quickshifter, which allows for clutchless upshifts, is a highly addictive feature once experienced. While not essential for performance, it significantly enhances the riding experience, especially in a racing environment where every fraction of a second counts.

Comparative Table: Stock vs. DNA High-Flow Air Filter

Frequently Asked Questions (FAQs)

Does the stock Kawasaki Ninja 400 air filter come pre-oiled?

No, the stock Kawasaki Ninja 400 air filter is a dry paper element and is not pre-oiled. It is designed to be a disposable component that is replaced during routine maintenance intervals, rather than cleaned and re-oiled.

How often should I clean or replace my Ninja 400 air filter?

For the stock paper filter, you should follow Kawasaki's recommended service intervals for replacement, typically every 12,000 miles or annually, depending on riding conditions. For a performance, reusable filter like the DNA unit, the cleaning interval will depend on your riding environment. In dusty conditions, it may need cleaning more frequently, whereas for track use, it might be cleaned after a few events. Always inspect the filter regularly and clean/re-oil when it appears dirty.

Do I need to remap my ECU after installing a high-flow air filter?

While installing only a high-flow air filter might not always necessitate an immediate ECU remap, it is highly recommended, especially if combined with an aftermarket exhaust system. A high-flow filter allows more air into the engine, which, without proper fuel mapping adjustments, can lead to a lean air/fuel mixture. Kits like the Graves Motorsports Power Up Kit include both the filter and a pre-tuned map to ensure optimal performance and engine longevity.

What are the main benefits of using a high-flow air filter?

The primary benefits of a high-flow air filter include improved engine airflow, which leads to increased horsepower and torque across the rev range, better throttle response, and enhanced fuel efficiency. Additionally, many high-flow filters are reusable, offering long-term cost savings compared to disposable stock filters.

Is the Graves Motorsports Power Up Kit street legal?

It's important to note the disclaimer provided by Graves Motorsports: these products are designed for closed-course and racing-use only. Regulations, especially in regions like California, are strict regarding emissions. Always perform due diligence and understand local laws before purchasing or installing performance parts on a road-registered vehicle.

In conclusion, while your stock Kawasaki Ninja 400 does not come with a pre-oiled air filter, the world of performance upgrades offers superior alternatives like the pre-oiled DNA high-flow filter. When integrated into a comprehensive package such as the Graves Motorsports Power Up Kit, alongside a full exhaust and ECU re-flash, the benefits are clear: a noticeable boost in power, improved throttle response, and a more engaging riding experience. For those looking to push their Ninja 400 to its limits on the track, or simply seeking to unlock its full potential, investing in these well-engineered components is a worthwhile endeavour. Remember, if you're considering the Graves kit, a discount code, such as 'ultimate', may be available for direct purchases.

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