Performance Times

    Harley-Davidson Stage 1, 2, 3, 4: Performance, Cost, & Alternatives

    by Matt VandenHeuvel / March 21, 2024

    Harley engine tuning

    Part of the fun of owning a Harley-Davidson motorcycle is making it your own by customizing your bike with upgrades and modifications. Though stock components are good enough for some -riders, major Harley enthusiasts seek to get the most out of their bikes with Stage 1, 2, 3, and even stage 4 upgrades. In this guide, we’ll explore the details of these upgrades, including the components, benefits, and considerations of each stage. From improved airflow and exhaust systems to advanced engine modifications, we’ll take a look at how these upgrades can take your Harley-Davidson motorcycle to new levels of performance and power.

    What is a Harley-Davidson Stage 1 Upgrade?

    A Stage 1 upgrade is a series of aftermarket modifications designed to enhance the performance and sound of a Harley-Davidson motorcycle. These modifications are popular among Harley riders looking to improve performance, throttle response, and overall riding experience in the most cost-effective way. Additionally, Stage 1 upgrades can also enhance the aesthetics of the motorcycle, as aftermarket air cleaners and exhaust systems come in various styles and finishes, allowing riders to personalize their bikes to their liking without making extensive upgrades.

    Cost of a Stage 1 Harley Upgrade

    On average, a Stage 1 upgrade for a Harley-Davidson motorcycle can cost anywhere from $500 to $1,500 or more, depending on the brand and quality of the aftermarket air intake, exhaust system, and engine tuning components selected. Installation costs may vary but are often included in the total price if performed by a professional. Since stage 1 Harley upgrades are fairly simple, most riders have no trouble making the upgrades themselves.

    Components of a Stage 1 Upgrade

    The specific components included in a Stage 1 upgrade vary depending on the model of the motorcycle and the preferences of the rider, but it commonly involves three main elements: air intake, exhaust system, and engine tuning.

    Air Intake

    Upgrading the air intake system to a high-flow air filter or air cleaner allows the engine to breathe more freely, increasing airflow and improving performance. 

    Exhaust System

    Installing a less restrictive aftermarket exhaust system can improve exhaust flow, adjust back pressure, and enhance the sound of the motorcycle. Many riders opt for a full aftermarket exhaust system to achieve a deeper, more aggressive exhaust note. However, many riders find that swapping the slip-on mufflers provides acceptable sound improvements and are satisfied with the less complex upgrade. 

    Learn more: Slip-On Exhaust Vs. Full-System: Which Is Right For You?

    Engine Tuning

    Re-mapping or re-tuning the motorcycle's engine control unit (ECU) using a fuel tuner or performance programmer ensures that the engine operates optimally with the upgraded air intake and exhaust components. This step helps maximize power gains and ensures the engine receives the proper air/fuel mixture for the new setup.

    What is a Harley-Davidson Stage 2 Upgrade?

    A Stage 2 upgrade for a Harley-Davidson motorcycle typically involves more extensive modifications than a Stage 1 upgrade, focusing on enhancing both the performance and capabilities of the bike. Overall, a Stage 2 upgrade is aimed at significantly increasing the performance and power output of the Harley, making it better suited for aggressive riding, track use, or other high-performance applications. Make sure the upgrades you choose are compliant with your state’s carbon emission restrictions before diving in.

    Cost of a Stage 2 Harley Upgrade

    Since a Stage 2 upgrade is more extensive than a Stage 1 upgrade, these modifications have a slightly higher price point. The cost of a Stage 2 Harley upgrade can range from $1,500 to $3,500 or more, depending on the specific components chosen and the complexity of the installation.

    Components of a Stage 2 Upgrade

    A Stage 2 upgrade often includes a cam upgrade and cylinder head work, as well as an upgraded fuel system, dyno tuning, and more.

    Camshaft Upgrade

    Upgrading to a higher-performance camshaft can further increase power and torque across the RPM range. Performance camshafts are designed to provide more lift and duration, allowing for increased airflow into and out of the engine cylinders.

    Learn more: Choosing The Right Cam For Your Harley-Davidson

    Upgraded Fuel System

    Upgrading the fuel system in a Harley is a more extensive upgrade, but can deliver significant benefits. This upgrade may include larger fuel injectors, a high-flow fuel pump, and/or a performance fuel pressure regulator to ensure adequate fuel delivery for the increased airflow and power demands of the engine.

    Dyno Tuning

    Tuning the motorcycle's engine control unit (ECU) on a dynamometer (dyno) is essential to optimize fuel and ignition timing settings for the new performance upgrades. Dyno tuning ensures that the engine operates efficiently and reliably while maximizing power gains.

    Alternative Upgrades

    Depending on your preferences and how you ride, additional modifications such as upgraded clutch components, transmission gear ratios, or suspension upgrades are also highly advisable additions to any of the standard stage 2 Harley upgrades.

    What is a Harley-Davidson Stage 3 Upgrade?

    A Stage 3 Upgrade represents a significant investment in performance modifications aimed at transforming a Harley-Davidson motorcycle into a high-performance machine capable of exhilarating acceleration and impressive power delivery. These modifications should be performed by experienced professionals familiar with Harley-Davidson engines and aftermarket upgrades to ensure proper installation and tuning. As with other upgrades, it's important to consider the potential impact on warranty coverage and emissions compliance when undertaking Stage 3 modifications.

    Cost of a Stage 3 Harley Upgrade

    Stage 3 upgrades are a significant investment in high-performance modifications for your Harley. As a result, the cost of a Stage 3 upgrade is typically higher, ranging from $3,000 to $7,000 or more, depending on the extent of the modifications and whether additional upgrades, such as high-performance throttle bodies or exhaust systems, are included.

    Components of a Stage 3 Upgrade

    A Stage 3 upgrade typically includes advanced performance enhancements aimed at maximizing power, torque, and overall performance. 

    Cylinder & Piston Kits

    This upgrade usually involves porting and polishing the cylinder heads for improved airflow, as well as installing high-performance valves, valve springs, and other valvetrain components to optimize combustion efficiency and power output. Additionally, installing aftermarket pistons and piston rings designed for higher compression ratios and improved durability can enhance engine performance and reliability. These upgrades are usually bundled in kits together, though you can buy individual components if you’re not ready for a complete overhaul.

    Big Bore Kit

    Installing a big bore kit involves increasing the displacement of the engine by either boring out the cylinders or replacing them with completely new, oversized cylinders, and installing larger pistons. This typically results in a significant increase in power and torque. This modification can substantially boost engine performance and is often a cornerstone of Stage 3 upgrades.

    Shop 136" & 131" Big Bore Stroker Cylinder & Piston Kits for 2017-Up M8 models →

    Shop 129" & 132" Big Bore Cylinder & Piston Kits for 2017-Up M8 models →

    High-Performance Camshaft

    Selecting a more aggressive camshaft profile designed for high-performance or larger displacement applications can optimize valve timing and lift characteristics, maximizing power delivery throughout the RPM range.

    Check out our comprehensive guide on S&S camshaft specs →

    Upgraded Valve Train Components

    Upgrading to high-performance valve springs, pushrods, and rocker arms can ensure reliable operation at higher RPMs and under increased stress, allowing the engine to achieve its full potential without sacrificing durability.

    Shop valve train components from S&S Cycle →

    Upgraded Exhaust System

    Upgrading to a high-flow exhaust system designed to complement the increased airflow of the Stage 3 modifications can help reduce back pressure and improve exhaust scavenging, contributing to overall performance gains.

    View S&S Cycle high-flow exhaust systems →

    Dyno Tuning

    Fine-tuning the engine's fuel and ignition mapping on a dynamometer (dyno) is crucial to optimize performance and ensure safe and reliable operation with the new modifications. Dyno tuning allows for precise adjustments to fueling and ignition timing to extract the maximum power and torque from the engine while maintaining reliability.

    What is a Harley-Davidson Stage 4 Upgrade?

    A Stage 4 upgrade consists of a comprehensive performance enhancement package that is aimed at significantly increasing the power, torque, and overall performance of your motorcycle. If you’re looking for a major overhaul of your motorcycle that delivers huge jumps in performance, a stage 4 upgrade is for you. Of course, you should always consider the potential impacts on reliability, warranty, and emissions compliance when undertaking these modifications.

    Cost of a Stage 4 Harley Upgrade

    As a rough estimate, a complete Stage 4 upgrade package, including high-performance engine components, exhaust system, air intake, tuning, and labor, could range anywhere from $3,000 to $10,000 or more. This cost can increase further if additional modifications, such as upgrading the clutch and transmission components, are included in the upgrade package.

    Components of a Stage 4 Upgrade

    High-Flow Throttle Body

    Installing a larger diameter throttle body with improved airflow characteristics can help maximize the amount of air entering the engine, further enhancing performance.

    High-Performance Cylinder Heads

    Upgrading to high-flow aftermarket cylinder heads with larger valves, improved port shapes, and optimized combustion chambers can further enhance airflow and combustion efficiency, contributing to increased power output and throttle response.


    A Stage 4 upgrade often requires a recalibration of the engine management system (ECU) to optimize fuel and ignition timing for the new performance components. This tuning can be done using aftermarket tuning devices or through Harley-Davidson's proprietary tuning software.

    Upgraded Clutch and Transmission Components

    In some cases, a Stage 4 upgrade may include upgrading the clutch and transmission components to handle the increased power and torque of the modified engine.

    Harley Davidson Stage 1, 2, 3 and 4 Comparison Chart





    Stage 1

    • Air intake
    • Exhaust
    • Engine tuning


    • improved airflow in engine
    • crisper throttle response and smoother acceleration
    • 5-10% increase in horsepower and torque
    • deeper, more aggressive exhaust note

    Stage 2

    • Cylinder and piston kit
    • Camshaft upgrade
    • Upgraded fuel system
    • Dyno tuning


    • 15% to 25% increase in horsepower and torque. 
    • higher RPM power and extending the usable power band
    • improved throttle response and acceleration

    Stage 3

    • Big bore kit
    • High-performance camshaft
    • Upgrade valve train components
    • Upgraded exhaust system
    • Dyno tuning


    • professional level performance boost
    • significant increases in horsepower and torque
    • greatest RPM increase
    • maximum engine efficiency

    Stage 4

    • High-performance cylinder heads
    • High-flow throttle body
    • Engine tuning
    • Upgraded clutch and transmission


    • increased horsepower and torque
    • overall performance boost


    Customize Your Ride

    The stages of Harley-Davidson upgrades offer riders a progressive path toward unlocking the full potential of their motorcycles. Whether you're seeking a modest increase in power and sound with a Stage 1 upgrade or aiming for high-performance thrills with Stage 4 modifications, there's a tailored solution to suit every rider's preferences and goals. By understanding the nuances of each stage and working with knowledgeable professionals like S&S Cycle, you can embark on a journey of customization that transforms your Harley-Davidson into a true reflection of your riding style and passion.

    Still want to go bigger? S&S Cycle has a variety of engines that can take your Harley to a whole new level. We’re talking extra power, torque, and responsiveness that’ll make your bike feel brand new.

    Shop all S&S engines today →

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    Tags: How-To / Tech

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