Choosing an aftermarket engine for a Harley Davidson requires balancing performance, compatibility, and budget. Among the best options in 2026 are the S&S Cycle 97&Prime, Big Bore Kit Black, which offers a straightforward upgrade for those seeking increased displacement; the MaxHiflo VTTOCK14 Complete Engine Oil Change Kit that’s ideal for maintaining high-performance engines; and the S&S 883 to 1200cc Conversion Kit designed specifically for riders looking to boost engine capacity without a full rebuild. Each option presents unique advantages and tradeoffs, so understanding the role, compatibility, and potential drawbacks will help you make a confident choice.
Complete the kit
Key Takeaways
- Big bore kits like the S&S 97&Prime offer increased displacement but may require mechanical expertise for installation.
- Complete oil change kits such as MaxHiflo provide essential maintenance that supports aftermarket engine longevity.
- Conversion kits like the S&S 883 to 1200cc are tailored for specific models, making them ideal for targeted upgrades.
- Performance parts from reputable brands tend to be more reliable but come at a higher cost.
- Compatibility and installation complexity are key factors influencing the best choice for your Harley.
| S&,S Cycle 97&Prime, Big Bore Kit Black 910-0205 |  | Best Overall Big Bore Upgrade | Application: 99-06 Big Twin (excluding 06 FXD) | Material: Cast aluminum | Finish: Black | VIEW ON AMAZON | See Our Full Breakdown |
| MaxHiflo VTTOCK14 Complete Engine Oil Change Kit for V-Twin Full Synthetic Harley Davidson Twin Cam, 6 quart |  | Best Maintenance Kit for Aftermarket Engines | Compatibility: Harley Davidson Twin Cam 2000-2015 | Oil Type: Full Synthetic 20w50 | Includes: Engine oil, primary oil, transmission oil, oil filter | VIEW ON AMAZON | See Our Full Breakdown |
| S&S 883 to 1200cc Black Cylinder & Piston Conversion Kit (910-0687) |  | Best for Model-Specific Capacity Increase | Application: XL883 86-21 | Size: 1200cc | Finish: Wrinkle Black | VIEW ON AMAZON | See Our Full Breakdown |
| S&S Cycle 07-Up Bigtwin TC3 Oil Pump Kit with Cam Plate |  | Best for Engine Durability & Oil System Upgrade | Compatibility: 07-up Bigtwin models | Material: Forged aluminum | Weight: 4.77 pounds | VIEW ON AMAZON | See Our Full Breakdown |
| S&S 106 in. Big Bore Black Kit for Harley Davidson 2006-2013 FXD and Big Twin Models |  | Best for Power and Displacement Increase | Application: 2006-2013 FXD and Big Twin | Size: 106 inches | Color: Black | VIEW ON AMAZON | See Our Full Breakdown |
| aftermarket engine for harley davidson motorcycle | Compatibility | Brand | Application | Material |
|---|---|---|---|---|
| S&,S Cycle 97&Prime | Harley Davidson Big Twin models 1999-2006 | S&S Cycle | 99-06 Big Twin (excluding 06 FXD) | Cast aluminum |
| MaxHiflo VTTOCK14 Complete Eng | Harley Davidson Twin Cam 2000-2015 | MaxHiflo | — | — |
| S&S 883 to 1200cc Black Cylind | Harley Sportster XL883 | S&S | XL883 86-21 | — |
| S&S Cycle 07-Up Bigtwin TC3 Oi | 07-up Bigtwin models | — | — | Forged aluminum |
| S&S 106 in. Big Bore Black Kit | Harley Davidson FXD 2006-2013 | S&S Cycle | 2006-2013 FXD and Big Twin | High-grade steel |
More Details on Our Top Picks
S&,S Cycle 97&Prime, Big Bore Kit Black 910-0205
The S&S Cycle 97&Prime Big Bore Kit stands out for delivering a significant increase in engine displacement, making it ideal for riders seeking more power without a full engine replacement. Compared to other kits, it’s designed specifically for 99-06 Big Twin models (excluding 06 FXD), offering a straightforward bolt-on process. However, this kit requires some mechanical skill for installation and may increase engine wear if not properly maintained. Its durability and proven performance make it a top choice for those wanting a reliable upgrade.
Pros:- Increases engine displacement significantly
- Designed specifically for 99-06 Big Twin models
- Durable construction and proven performance
Cons:- Requires mechanical expertise for installation
- May increase engine wear if not maintained properly
Best for: Riders looking for a reliable, straightforward displacement boost for classic Harley Big Twins.
Not ideal for: Beginners or those who prefer a plug-and-play solution without mechanical work.
- Application:99-06 Big Twin (excluding 06 FXD)
- Material:Cast aluminum
- Finish:Black
- Compatibility:Harley Davidson Big Twin models 1999-2006
- Installation Difficulty:Moderate
- Power Gain:Up to 20%
- Brand:S&S Cycle
Our verdict“Best overall big bore upgrade for experienced riders wanting more power from classic Harley engines.”
MaxHiflo VTTOCK14 Complete Engine Oil Change Kit for V-Twin Full Synthetic Harley Davidson Twin Cam, 6 quart
The MaxHiflo VTTOCK14 Kit is tailored for maintaining Harley engines, especially after aftermarket modifications. It includes high-quality synthetic oils and a premium filter, making it ideal for extending engine life and ensuring smooth operation. Compared with raw performance parts, this kit emphasizes durability and protection, which is vital for engines with increased power or displacement. Its comprehensive nature makes it suitable for riders who want to keep their upgraded engines running at peak condition, though it doesn’t directly boost performance.
Pros:- Includes high-quality synthetic oils and filter
- Designed for Harley Davidson Twin Cam engines 2000-2015
- Extends engine and transmission life
Cons:- Does not provide performance enhancement
- Primarily a maintenance product, not a performance upgrade
Best for: Harley owners who want to preserve and maintain their aftermarket or stock engines reliably.
Not ideal for: Those seeking performance upgrades rather than routine maintenance.
- Compatibility:Harley Davidson Twin Cam 2000-2015
- Oil Type:Full Synthetic 20w50
- Includes:Engine oil, primary oil, transmission oil, oil filter
- Quantity:6 quarts total
- Brand:MaxHiflo
- Made in:USA
Our verdict“A highly recommended maintenance kit for keeping aftermarket engines in top shape over time.”
S&S 883 to 1200cc Black Cylinder & Piston Conversion Kit (910-0687)
This S&S Conversion Kit is tailored for riders with XL883 models, providing a simple way to boost engine capacity from 883cc to 1200cc. It’s ideal for those who want more power without a complete engine rebuild. Compared to big bore kits designed for big twins, this kit is a targeted solution for sportster models, offering a cost-effective upgrade. The main tradeoff? It requires mechanical skill for installation, and increased displacement can lead to engine wear if not properly maintained.
Pros:- Easy upgrade for XL883 models
- Increases capacity to 1200cc
- High-quality components and finish
Cons:- Installation requires mechanical skill
- Potential for increased engine wear if not maintained
Best for: Sportster owners seeking a straightforward capacity increase for more power.
Not ideal for: Owners of larger Harley models or those unfamiliar with engine internals.
- Application:XL883 86-21
- Size:1200cc
- Finish:Wrinkle Black
- Includes:Cylinder, piston, rings, gasket, manual
- Compatibility:Harley Sportster XL883
- Brand:S&S
Our verdict“Ideal for Sportster owners wanting a simple, effective capacity boost without a full engine swap.”
S&S Cycle 07-Up Bigtwin TC3 Oil Pump Kit with Cam Plate
This S&S Oil Pump Kit enhances engine durability by improving oil flow and pressure, crucial for high-performance or heavily modified engines. Made from CNC-machined forged aluminum, it provides increased strength and stability. Compared with standard oil pumps, it offers adjustable pressure regulation and debris protection, making it a smart choice for riders pushing their engines harder. The main limitation? It’s designed specifically for 07-up Bigtwin models, which means compatibility is restricted, and installation can be complex for less experienced mechanics.
Pros:- High-quality CNC-machined forged aluminum
- Enhanced durability with debris protection
- Adjustable oil pressure regulation
Cons:- Limited to 07-up Bigtwin models
- Installation may require technical expertise
Best for: Harley owners with Bigtwin models seeking improved oil system reliability for performance or longevity.
Not ideal for: Owners of older models or those not comfortable with technical installation.
- Compatibility:07-up Bigtwin models
- Material:Forged aluminum
- Weight:4.77 pounds
- Made in:USA
- OEM Part Number:310-0732
Our verdict“A solid upgrade for Bigtwin owners focused on engine longevity and performance stability.”
S&S 106 in. Big Bore Black Kit for Harley Davidson 2006-2013 FXD and Big Twin Models
The S&S 106 in. Big Bore Kit is designed for riders aiming to significantly increase their Harley engine’s displacement. Suitable for 2006-2013 FXD and Big Twin models, this kit boosts power by enlarging the engine to 106 inches, offering a noticeable performance upgrade. Compared to smaller bore kits, it delivers more torque and acceleration, but the larger displacement may require additional modifications and more frequent maintenance. Installation isn’t beginner-friendly and should be approached with mechanical competence in mind.
Pros:- Increases displacement to 106 inches
- Designed specifically for Harley FXD and Big Twin models
- Durable and high-quality construction
Cons:- Requires mechanical expertise for installation
- Potentially increased engine wear if not maintained properly
Best for: Harley owners seeking serious power gains for Big Twin models with a focus on performance.
Not ideal for: Casual riders or those uncomfortable with complex engine work.
- Application:2006-2013 FXD and Big Twin
- Size:106 inches
- Color:Black
- Compatibility:Harley Davidson FXD 2006-2013
- Material:High-grade steel
- Power Gain:Up to 25%
- Brand:S&S Cycle
Our verdict“Best suited for riders demanding substantial performance upgrades on larger Harley engines.”
How We Picked
Our selection process focused on compatibility with Harley Davidson models, especially those with similar engine configurations. We prioritized products that balance performance enhancements with ease of installation and reliability. Key criteria included brand reputation, user reviews, and technical specifications. We also considered the role each product plays — whether it’s a performance upgrade, maintenance part, or conversion kit — to ensure options meet different rider needs and skill levels.
| aftermarket engine for harley davidson motorcycle | Material | Brand |
|---|---|---|
| S&,S Cycle 97&Prime | Cast aluminum | S&S Cycle |
| MaxHiflo VTTOCK14 Complete Eng | — | MaxHiflo |
| S&S 883 to 1200cc Black Cylind | — | S&S |
| S&S Cycle 07-Up Bigtwin TC3 Oi | Forged aluminum | — |
| S&S 106 in. Big Bore Black Kit | High-grade steel | S&S Cycle |
Factors to Consider When Choosing Aftermarket Engine For Harley Davidson Motorcycles
When selecting an aftermarket engine component for your Harley Davidson, it’s essential to consider your riding style, mechanical skill level, and the specific model compatibility. Whether you’re after a simple displacement boost, a complete engine overhaul, or just maintenance parts to keep your engine running smoothly, understanding the role each product plays will help you make smarter choices. Keep in mind that higher performance parts often come with increased installation complexity and maintenance needs.Performance Upgrades
Big bore kits and conversion cylinders increase engine displacement and power. They are ideal for riders seeking more acceleration and torque but require mechanical skills for installation. Compatibility with your specific Harley model is critical, so double-check specifications before purchasing.
Maintenance and Support
High-quality oils and filters support the longevity of aftermarket engines. Regular maintenance kits like the MaxHiflo ensure your engine stays in top condition, especially when running higher performance parts that generate more heat and wear.
Engine Durability and Longevity
Upgrades like oil pumps and reinforced components help extend engine life, particularly if you push your Harley with more power. These parts often require technical installation but can greatly improve reliability for high-mileage or high-performance builds.
Frequently Asked Questions
Can I install a big bore kit on any Harley Davidson engine?
Big bore kits are typically designed for specific Harley models and engine years. It’s essential to verify compatibility with your motorcycle’s make and model before purchasing. Installing a kit on an incompatible engine can lead to fitment issues and potential damage.
Do aftermarket engines or components void Harley warranty?
Most aftermarket parts can void portions of the Harley warranty if installed improperly or if they cause damage. It’s advisable to consult your dealer and review warranty terms before making modifications, especially if your bike is still under warranty.
Is professional installation recommended for performance upgrades?
Yes, many performance upgrades like big bore kits or oil pumps require technical expertise. While some riders with mechanical skills can install these parts, professional installation can ensure proper fit, function, and long-term reliability.
How does increasing displacement affect engine wear?
Increasing displacement generally puts more stress on engine components, which can accelerate wear if the engine isn’t properly maintained. Upgrading cooling, lubrication, and using high-quality parts can mitigate these effects.
What maintenance should I expect after installing a performance engine part?
Performance upgrades often necessitate more frequent oil changes, inspection of internal parts, and possibly adjustments to the engine’s tuning. Regular maintenance is critical to preserve reliability and achieve the desired performance gains.
Conclusion
If you’re an experienced rider comfortable with mechanical work and want a noticeable power boost, the S&S 97&Prime Big Bore Kit or the S&S 106 Big Bore Kit offers excellent value. For those focusing on engine longevity and routine maintenance, a comprehensive oil change kit like MaxHiflo is ideal. Beginners or riders seeking plug-and-play solutions should avoid complex kits and stick to maintenance products or professional installations. No matter your skill level, prioritizing compatibility and quality will result in a more satisfying upgrade.
