Harley-Davidson FAT BOY GRAY GHOST Big Bore Kits

Genuine Harley-Davidson

This kit was developed for the budget minded rider who wants to experience an adrenalin-pumping burst of speed on the way to the red line. The additional power starts to build at 3000 RPM and increases by up to 24% at the red line. When riding aggressively, you must downshift to lower gears to keep the engine in the higher RPM range. Ideal for riders looking for excitement and willing to ride in the upper RPM range. Produces greater acceleration in the mid and upper RPM range. Minimally invasive, requiring only the opening of the cam chest. Retains Original Equipment Factory Warranty. Includes covers in gloss black. Stage II Upgrade.

Genuine Harley-Davidson

3-7/8" Standard Bore. When combined with stock cylinder heads, these forged 3-7/8" pistons boost the compression ratio of your 3-7/8" big bore cylinder set-up. The combination results in a compression ratio of 10.5:1. Piston skirts feature a unique black coating for improved wear-resistance, better fit and reduced noise. These pistons include Titanium SST rings to withstand the stresses seen in racing. Complete kit includes pistons, rings, wrist pins and clips.

Genuine Harley-Davidson

When it comes to increasing engine power, there is no substitute for more cubic inches. With efficient filling of the air/fuel mixture, the bigger the displacement, the more power your engine can produce. In the past, the only way to increase the bore of your 96 or 103 cubic inch Twin Cam V-Twin motor was to tear down the motor and re-bore the engine cases to fit larger bore cylinder spigots. It was a labor-intensive and expensive process. Now, you can take your 96 or 103 cubic inch motor to a full 110 cubic inches without removing the engine from the chassis. The Screamin' Eagle team has engineered a 4" Big Bore Cylinder and Piston package that increase the internal bore from 3-7/8" to 4", without increasing the outside diameter of the cylinder spigot. The cylinder slips into the existing case bore without modification. This kit will add a whopping 7 cubic inches of displacement for more torque throughout the RPM range. The kit includes front and rear cylinders, system-matched pistons with rings and breathers.

Genuine Harley-Davidson

This multi-layered head gasket provides improved sealing for 3-7/8" Big Bore high performance engines. Sold in pairs.

Genuine Harley-Davidson

If you're looking to build a fast, track-ready 103, this kit eliminates the guess work. Kit includes CNC-Ported Factory Cylinder Heads with high performance valve springs, matching high-compression forged aluminum 10.5:1 pistons, SE-259E cams for higher lift for a given duration, Perfect-Fit Pushrods to accommodate the higher cam lift, and a 58mm throttle body with High Flow Injectors to feed the beast. Kits for Twin Cam 96 models include Big Bore cylinders, and the Twin Cam 103 kit uses the Original Equipment 103 cylinders. The kit also includes high-performance clutch spring and sprocket retention hardware to put the power to the ground. Kit includes top end gaskets.

Genuine Harley-Davidson

Go big or go home. With the largest displacement of any Harley-Davidson Stage Kit, this 107CI to 128CI Stage IV Kit is designed to deliver maximum horsepower - all the way to the redline. Packaged with patent-protected cylinder technology, it allows for the largest bolt-on engine upgrade to any Milwaukee-Eight motor. Features new CNC-ported heads with 1mm bigger valves and fully machined combustion chambers. Coupled with the kit's high-lift SE8-517 cam, high compression pistons and a 64mm throttle body and intake manifold, this combination delivers a thrilling 135 ft-lb of torque and 124 HP rear-wheel output when paired with Screamin' Eagle Street Cannon Mufflers for 131 kit customers. It's designed to run wide open at high-end RPMs and provide a significant boost of torque from cruising speed. You'll feel the difference as soon as you twist the throttle. Delivers increased response throughout the entire RPM range. Provides thrilling acceleration when twisting the throttle. Maintains flat torque curve from cruising RPM to redline. Can be installed without removing the engine from chassis. Includes CNC Ported Cylinder Head with CNC machined chamber and 1mm larger valves, 131 Stage IV Timer cover, SE8-517 High-Lift Cam, Forged High Compression Pistons. Also includes High Performance Cam Bearing and High Performance Tappets, 4.31" Steel Sleeve Cylinders, 64mm Throttle Body and Cast Manifold, High Flow Injectors (5.5 g/sec). Pending 49-State U.S. EPA compliant.

Genuine Harley-Davidson

The most advanced Twin Cam performance cylinder head design available. Screamin' Eagle CNC Ported Maximum Velocity Area (MVA) cylinder heads create power across the entire RPM range by maximizing velocity through the intake ports. Increased air speed velocity through the ports is achieved by "right sizing" port volume at 98cc, lowering the port roof, and by precision-machining the shape of the port to complement the giant 2.120" intake valves. Screamin' Eagle CNC-Ported MVA Cylinder Heads conquer a unique engineering challenge, and provide the highest possible torque and acceleration at any RPM. MVA Heads will boost the punch of a 103" engine. When paired with high lift cams, MVA Heads can give a 110" or 113" motor everything it needs to achieve new levels of performance. Countless hours of dyno testing resulted in a 95cc combustion chamber that performs in perfect balance with the port size and shape, and reduced detonation. MVA Heads feature Screamin' Eagle Race Springs that permit the use of high lift cams (up to.660"), and are machined to accept automatic compression releases (sold separately) for easier starting. MVA Heads are manufactured and assembled at Harley-Davidson's world class engine factory in Milwaukee, ensuring every set is made to exact tolerances.

Genuine Harley-Davidson

3-7/8" Standard Bore. These Flat-Top Cast Pistons are designed for use with 3-7/8" Big Bore performance cylinders (1550). Kit includes rings, clips and pins.

Genuine Harley-Davidson

This Stage IV Kit was developed to deliver maximum horsepower from the Milwaukee-Eight engine - all the way to the redline. The system-matched combination of larger displacement cylinders, free flowing CNC-Ported cylinder heads and a cam with the highest available valve lift are the starting point to building the perfect engine for the performance junkie. Designed for a high level of flexibility, this package is ideal for riders who like to comfortably cruise at lower rpm but still have plenty of arm-pulling acceleration when you whack the throttle. Kit includes CNC Ported Cylinder Heads with Performance Valve Springs, 64mm Throttle Body, High Flow Injectors (5.5g/s), 4.075" Bolt-On Cylinders, Forged 11:1 High Compression Aluminum Coated Pistons and Rings, SE8-515 Cam, Cam Bearing Upgrade, High Performance Tappets, Multi-layer Coated Head Gaskets, High Capacity Clutch Springs (1200N) and most necessary gaskets and seals. Increases power by up to 40% when compared to the Original Equipment engine configurations. Delivers increased response throughout the entire RPM range. Maintains flat torque curve from cruising RPM to redline. Can be installed without removing the engine from the chassis. Retains Original Equipment Factory Warranty. 50-State U.S. EPA compliant. Includes Screamin' Eagle Cylinder Heads with Performance Valve Springs, Throttle Body, High Flow Injectors, Bolt-On Cylinders, Pistons, Piston Rings, Cam, Cam Bearings, Tappets, Head Gaskets, Top End, Cylinder Base and Cam Cover Gaskets, and Clutch Springs.

Genuine Harley-Davidson

This kit was developed for the budget minded rider that wants to experience that adrenalin-pumping burst of speed while heading toward the red line. The additional power starts to build @ 3000 RPM and continues to build by up to 24% at redline. Riding the bike aggressively will require downshifting to lower gears to keep the engine operating in the higher RPM range. Ideal for riders looking for excitement and are willing to ride in the upper RPM range. Produces greater acceleration in the mid and upper RPM range. Minimally invasive, only requiring opening of the cam chest. Retains Original Equipment Factory Warranty. 50-State U.S. EPA compliant.

Genuine Harley-Davidson

Build a fast, reliable 110 cubic inch Twin Cam hauler without having to remove the motor from the chassis. This Stage III Street Performance Kit combines system-matched Screamin' Eagle big bore cylinders, high compression pistons and performance cams and valve train components with the Original Equipment cylinder heads for a cost-effective boost in torque and performance.

Genuine Harley-Davidson

This kit was developed for the budget minded rider that wants to experience crisp throttle response and acceleration they can feel at slower speeds. The 5% increase in torque can be felt immediately off the line and continues to build by up to a 14% increase @ 4500 RPM - the ideal power band for passing slow moving vehicles. Delivers enhanced torque and horsepower in the low to mid RPM range. Produces passing power without a downshift or high revs. Minimally invasive, only requiring opening of the cam chest. Retains Original Equipment Factory Warranty. Includes Gloss Black covers. Stage II Upgrade.

Genuine Harley-Davidson

This Stage IV Kit was developed to deliver maximum horsepower from the Milwaukee-Eight engine - all the way to the redline. The system-matched combination of larger displacement cylinders, free flowing CNC-Ported cylinder heads and a cam with the highest available valve lift are the starting point to building the perfect engine for the performance junkie.

Genuine Harley-Davidson

This kit was developed for the budget minded rider that wants to experience crisp throttle response and acceleration they can feel at slower speeds. The 5% increase in torque can be felt immediately off the line and continues to build by up to a 14% increase @ 4500 RPM - the ideal power band for passing slow moving vehicles. Delivers enhanced torque and horsepower in the low to mid RPM range. Produces passing power without a downshift or high revs. Minimally invasive, only requiring opening of the cam chest. Retains Original Equipment Factory Warranty. 50-State U.S. EPA compliant.

Genuine Harley-Davidson

This 4-3/8" stroker flywheel assembly can be combined with 3-7/8" cylinders and pistons to produce 1690cc (103") displacement, 4.00" cylinders and pistons for 1800cc (110"), or with 4.060" cylinders and pistons for 1856cc (113") displacement.

Genuine Harley-Davidson

4.060" Standard Bore. Forged from high-strength aluminum, these 10.5 to 1 ratio pistons feature nickel-plated surfaces for enhanced durability, and a special Teflon coating for improved wear-resistance required for racing applications. These pistons include Titanium SST rings to withstand the stresses seen in racing. Complete kit includes pistons, rings, wrist pins, and clips.

Genuine Harley-Davidson

Go big or go home. With the largest displacement of any Harley-Davidson Stage Kit, this 107CI to 128CI Stage IV Kit is designed to deliver maximum horsepower - all the way to the redline. Packaged with patent-protected cylinder technology, it allows for the largest bolt-on engine upgrade to any Milwaukee-Eight motor. Features new CNC-ported heads with 1mm bigger valves and fully machined combustion chambers. It's designed to run wide open at high-end RPMs and provide a significant boost of torque from cruising speed. You'll feel the difference as soon as you twist the throttle. Delivers increased response throughout the entire RPM range. Provides thrilling acceleration when twisting the throttle. Maintains flat torque curve from cruising RPM to redline. Can be installed without removing the engine from chassis. Includes CNC Ported Cylinder Head with CNC machined chamber and 1mm larger valves, 128 Stage IV Timer cover, SE8-517 High-Lift Cam, Forged High Compression Pistons. Also includes High Performance Cam Bearing and High Performance Tappets, 4.31" Steel Sleeve Cylinders, 64mm Throttle Body and Cast Manifold, High Flow Injectors (5.5 g/sec). Pending 49-State U.S. EPA compliant.