S&S Cycle 98″ Big Bore Kit For Harley Big Twin 1999-2006

Unlocking Performance: The S&S Cycle 98″ Big Bore Kit for Harley Big Twin (1999-2006)

The pursuit of increased power, torque, and overall performance is a core tenet of Harley-Davidson ownership. For riders looking to significantly elevate their Twin Cam experience without a complete engine teardown, the S&S Cycle 98″ Big Bore Kit represents one of the most effective and popular bolt-on solutions available. Specifically designed for 1999–2006 Harley-Davidson Big Twin models (excluding 2006 Dyna models, which use a different rod length), this kit transforms the stock 88 cubic inch (1450cc) engine into a potent 98 cubic inch (1600cc) powerhouse.
Engineering and Design Excellence

S&S Cycle, a name synonymous with high-performance V-Twin components, engineered this kit to maximize efficiency and longevity. The heart of the upgrade lies in the replacement cylinders and pistons.
High-Quality Cylinders

The kit features new, high-quality cast iron cylinders with a durable finish, designed to match the stock Harley aesthetic, often available in a factory-matching wrinkle black or silver powder coat. The increased bore diameter is the key to the displacement bump. Unlike some lesser kits, S&S ensures their cylinders offer superior thermal stability. Better heat dissipation is crucial in air-cooled V-Twins, preventing performance-robbing heat soak and contributing to the engine’s overall durability, even under high-load conditions.

Forged Pistons and Rings

Central to the power increase are the meticulously designed forged pistons. Forged pistons are inherently stronger than cast alternatives, providing the necessary resilience to handle the higher compression ratios and increased combustion pressures generated by the big bore setup. S&S typically provides a higher-than-stock compression ratio (often around 10.5:1, depending on the specific kit variant and head configuration). This elevated compression directly translates into a significant increase in torque and horsepower across the entire RPM range. The pistons are accompanied by a high-performance ring set that minimizes blow-by, ensuring maximum cylinder sealing for consistent power output and reduced oil consumption.

Performance Gains and The “Bolt-On” Advantage

The primary appeal of the S&S 98″ kit is the dramatic increase in performance paired with relative ease of installation.
Significant Power Boost

A stock 88″ Twin Cam typically produces around 60-65 horsepower and 75-80 ft-lbs of torque at the rear wheel. When properly installed and paired with complementary upgrades (such as a performance camshaft, high-flow air cleaner, and a 2-into-1 exhaust system), the S&S 98″ Big Bore Kit can help the engine achieve rear-wheel power figures well into the 90-100 horsepower range and 100+ ft-lbs of torque. This transformation fundamentally changes the bike’s character, offering quicker acceleration, stronger passing power, and a more responsive throttle feel.
The Bolt-On Advantage

The S&S 98″ kit is renowned for being a true “bolt-on” upgrade. For the 1999-2006 Twin Cam, this means that the new cylinders do not require the stock crankcases to be bored or machined. The outer diameter of the S&S cylinder spigot is designed to fit precisely into the stock crankcase bore. This feature drastically reduces the complexity, cost, and downtime associated with engine modification, making it accessible to competent home mechanics and minimizing labor costs at the dealership or independent shop.
Comprehensive Kit Contents and Integration

The S&S 98″ Big Bore Kit is typically a complete package designed for hassle-free integration. While the exact contents may vary slightly, a standard kit usually includes:

Two Big Bore Cylinders (98″ size).

Two Forged Piston Assemblies (Pistons, wrist pins, clips).

High-Performance Piston Rings.

Complete Gasket Set (Head, base, and exhaust gaskets for reassembly).

Required Supporting Modifications

While the kit itself is bolt-on, maximizing the performance of the new 98 cubic inch motor requires attention to supporting systems:

Fuel Management/Tuning: The increased displacement and compression necessitate changes to the air/fuel ratio and ignition timing. A high-quality fuel management system (like an S&S tuner, Dynojet Power Vision, or ThunderMax) and a proper dyno tune are absolutely critical for safe and effective operation. Running the new engine too lean will lead to overheating and catastrophic failure.

Camshaft Upgrade (Highly Recommended): The stock H-D camshafts are typically too mild to take full advantage of the increased displacement and compression. Pairing the 98″ kit with an S&S performance cam (e.g., a 510G or 570G cam for gear-drive, or a chain-drive equivalent) is highly recommended to shift the powerband and achieve the maximum torque and horsepower figures advertised.

Air Cleaner and Exhaust: A high-flow air cleaner and a performance exhaust system are essential to allow the larger engine to breathe effectively, maximizing both intake and exhaust efficiency.
Compatibility and Model Specificity

It is crucial to note the specific model years covered by this kit: 1999 through 2006 Harley-Davidson Big Twins.

A critical caveat exists for the 2006 model year: The kit is compatible with 2006 Softail, Touring, and other non-Dyna Big Twins. However, the 2006 Dyna model (and all 2007-later Twin Cams) introduced a new longer connecting rod (a 4-3/8″ stroke vs. the earlier 4″ stroke). Because of this difference, 2006 Dyna models require a different piston/cylinder combination. Buyers must confirm their specific year and model to ensure they purchase the correct kit to match their engine’s internal geometry.

In conclusion, the S&S Cycle 98″ Big Bore Kit stands as an industry benchmark for performance enhancement on the early Twin Cam platform. It offers a reliable, well-engineered path to substantial power gains, making the 1999-2006 Harley Big Twin models feel like an entirely new machine, ready for the next level of riding aggression.

S&S 98″ Big Bore Kit For Harley Big Twin
Features

The largest bore, 3.937″ that can fit into a stock engine
Bolt on kits make installation as easy as possible
There is no machining required for the case nor do the pistons require boring or honing
Cylinders have 11 fins and are designed to resemble the OEM shape and color
Each cylinder liner is centrifugal cast, and features 40,000 psi tensile strength for superior wear and performance
CP pistons, industry leaders, complete this kit and provide exceptional wear, noise characteristics, as well as performance
Pistons are complete with rings, wristpins, and wristpin clips
Comes with top and bottom cylinder gaskets

Made in the USA

Product Style	AmericanV-twin Item #	Catalog Number	Store Sku	MFR. Product #	Availability
Black	1073410	176-964	314666	910-0481	In Stock: Ships within 24 hours
Silver	1073411	176-963		910-0482	Only 1 Left: Ships next business day

This Product Fits

Harley Davidson
Dyna Convertible FXDS 1999, 2000
Dyna Low Rider FXDL/I 1999-2006
Dyna Street Bob FXDB/I 2006
Dyna Super Glide Custom FXDC/I 2005, 2006
Dyna Super Glide FXD/I 1999-2006
Dyna Super Glide Sport FXDX 1999-2005
Dyna Super Glide Sport Touring FXDXT 2001, 2002, 2003
Dyna Wide Glide FXDWG/I 1999-2006
Electra Glide Classic FLHTC/I 1999-2006
Electra Glide Standard FLHT/I 1999-2006
Electra Glide Ultra Classic FLHTCU/I 1999-2006
Road Glide FLTR/I 1999-2006
Road King Classic FLHRC/I 1999-2006
Road King Custom FLHRS/I 2004, 2005, 2006
Road King FLHR/I 1999-2006
Softail Deluxe FLSTN/I 2005, 2006
Softail Deuce FXSTD/I 2000-2006
Softail Fat Boy FLSTF/I 2000-2006
Softail Heritage Classic FLSTC/I 2000-2006
Softail Heritage FLST/I 2006
Softail Heritage Springer FLSTS/I 2000, 2001, 2002, 2003
Softail Night Train FXSTB/I 2000-2006
Softail Springer Classic FLSTSC/I 2005, 2006
Softail Springer FXSTS/I 2000-2006
Softail Standard FXST/I 2000-2006
Street Glide FLHX/I 2006