Hammer Performance - for All Your Harley Davidson XL Sportster and Big Twin Performance Needs
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BIG BORE KITS

For Sportster & Buell

Quick Links:


BOLT-ON 1250 Kits from HAMMER PERFORMANCE

For 1986-present 883 & 1200cc Sportsters and Buells - From $599.95

New Low Price on 86-03 Small Fin Kits!

Black 2004-Present 1250 Kit for Harley Davidson XL Sportster or Buell
2004-Up (Big Fin) Bolt-On 1250 Kit in Black - With 30 Degree Reverse Dome Pistons

Our 1250 Kits let you take your Sportster or Buell out to 1250cc with no case boring required. It's a bolt-on kit that can be installed in an afternoon without removing your engine from the frame!


Each kit comes standard with the best components on the market:


Sledge Hammer cylinders feature an extra heavy duty iron liner and aluminum fin construction. This design gives the best of both worlds: a strong, stable bore for maximum ring seal and the heat dissipation you need for extreme conditions. The iron liner material is also rock hard for a long, trouble free life.


Lightweight High Performance 1250cc 30 Degree Reverse Dome Forged Piston for Harley Davidsons and Buells Complementing these great cylinders is a set of our exclusive forged Sledge Hammer pistons. These pistons are lighter than the competition's for more power, less vibration, and less wear and tear on the lower end. Click here to see how dramatically lighter these pistons are than the competition's offering. And they're actually stronger as well! They feature extra large valve pockets for those radical cams, anti-detonation grooves, dual wrist pin oilers, expansion grooves for superior ring seal, and ribbing to give maximum strength with minimum weight. You cannot find a finer piston for your HD or Buell. Now available in our exclusive 30 degree reverse dome design, for maximum chamber efficiency with a pump-gas friendly compression ratio!


Unlike some of the other kits out there, we custom hone every set of cylinders to the exact set of pistons that are included in the kit. This gives a much more precise fit than you can get when slapping together off-the-shelf cylinders and pistons, resulting in better ring seal and longer life. Close is not good enough, we want it perfect!


Lightweight High Performance Forged Pistons for Harley Davidsons and Buells


For the ultimate in convenience, add our pre-assembly option to your engine kit. We'll thoroughly clean your cylinders, precisely gap your rings, and then pre-lube and assemble the pistons and rings into the cylinders. The ready-to-install assembly will then be shipped to you in a sealed plastic bag to keep it clean and safe. This service makes the installation a breeze, as you simply lower the piston down enough in the bore to expose the wrist pin hole, position it over the connecting rod, insert the wrist pin and circlip, and push the cylinder down into position. No special tools required!


Note: 04-up style large fin cylinders will fit on 86-03 bikes. 86-03 style small fin cylinders will fit on 04-up bikes with some slight grinding on the lowest fin on the pushrod side.


Tech Tip: Are you converting an 883? Be sure to read our tech article on conversions for lots of good information to make your project a success!


GET THE BEST! GET A 1250 KIT FROM HAMMER PERFORMANCE TODAY!

Hammer Performance 1250 Kits for Sportsters & Buells

Heads

Dome Type

Compression
Ratio

Select Year & Color

86-Present XL883
for use with 883 heads only

Reverse

10:1 @49cc

88-03 XL1200
95-96 Buell S2

Radius

10.5:1 @67cc

98-03 XL1200S
96-03 SE/Lightning
96-98 Buell S1
97 Buell S3
97-98 Buell M2
(Lightning Heads)

10 Degree

10.5:1 @62cc

98 Buell S1W & S3
99-02 Buell all

15 Degree

10.5:1 @67cc

Custom Application
See Note 1
for use with 883 heads only

30 Degree
Reverse Dome

10.5:1 @61cc

Custom Application
See Note 1

30 Degree
Reverse Dome

10.5:1 @72cc

Custom Application
See Note 1

30 Degree
Reverse Dome

10.5:1 @76cc

Custom Application
See Note 1

30 Degree
Reverse Dome

10.5:1 @80cc

86-87 XL1100
04-present XL1200
04-present SE
04-10 Buell XB12

Rectangular

10.5:1 @62cc

Custom Application

Flat Top

9:1 @67cc

Race Application

30 degree x .400

Machine for
Desired CR
Note 2


Note 1: the 30 degree x .400 and 30 degree Reverse Dome pistons require your chambers be machined to match. HAMMER PERFORMANCE can handle this service for you.
Note 2: the 30 degree x .400 dome race pistons are designed to be cut down to achieve your desired compression ratio, call for details
Note 3: 1250 kits are also available with AXTELL full cast iron cylinders on a special order basis. Axtell cast iron cylinders offer the ultimate in bore stability and ring seal but have a weight penalty of approximately 6lbs per cylinder. They are highly recommended for maximum effort engines.


PLEASE NOTE:

Depending on the year of your bike, other components are necessary for a successful conversion. Specifically:

  • All 86-06 models need a new ignition system, to provide a timing curve that's appropriate for the 1250 kit
  • All carbureted models (86-06) need a couple of carb jets, to properly adjust the fuel delivery for the larger displacement
  • All injected models (07-Up) need a flash type tuner to adjust both timing and fueling
  • All 04+ 883 models need a new clutch spring at a minimum, however an extra plate clutch pack is recommended to eliminate a common point of failure in the stock clutch
Although these items may be found elsewhere on the site, we have included them in the table below for convenience.


1250 Kit Options

Description

Add to Cart

Gap Rings and Pre-Assemble Engine Kit ($40)

Upgrade Head & Base Gasket to Full Top End Gasket Set ($40)

Ignition System - Required for all 86-06 models
Notes:
Nose cone modules were original in 98-03 and can be fitted to any 86-03
1005S-EX is a plug-and-play nose cone module for 98-03
7-pin modules are plug-and-play for 90-93
8-pin modules are plug-and-play for 94-97
we recommend nose cone modules for 86-89

DynoJet PowerVision EFI Flash Tuner - Required for all 07+ models

Clutch Upgrade - Required for all 04+ 883 models

Clutch Spring Compressor Tool
Note: This tool is required to change the clutch spring or clutch pack
High quality tool from Motion Pro

Primary Gasket
This is a high quality rubber coated steel primary gasket

CV Main Jet - Required for all 88-06 models
Note: most basic conversions will run best with a 185 or 190
Note 2: if you have an 86-87 model with the original carb, please contact us for jets

CV Pilot Jet - recommended for all 88-06 models
Note: a 45 is generally the best pilot jet

Tip: Choose your top end gasket set based on the type of rocker boxes you're using. The head and base gaskets all interchange from 1986-present.
Tip 2: Head gasket thickness is chosen to optimize squish clearance. Read more about squish clearance here. The size your motor will want is a function of a whole bunch of tolerance stack-up, much of which is on parts of your motor that are not part of your engine kit. Therefore it's impossible to predict with 100% certainty which gasket thickness you'll want. However, practical experience has shown that the .030 head gasket/.020 base gasket combination gives a good squish clearance more than 95% of the time. Most customers use .030 gaskets, never check squish clearance, and problems are almost non-existent. So our advice is to get the .030 head gasket kit, and if it proves to be too thin, let us know and we'll get you some .040 gaskets.


Silver 1250 Kit for High Performance Harley Davidson XL Sportster or Buell
2004-present Style Bolt-On 1250 Kit in Silver
Reverse Dome Conversion Pistons for 883 Heads


Black 1250 Kit for High Performance Harley Davidson XL Sportster or Buell
1986-2003 Style Bolt-On 1250 Kit in Black
15 Degree Domed Pistons for Thunderstorm Heads


Silver 1250 Kit for High Performance Harley Davidson XL Sportster or Buell
1986-2003 Style Bolt-On 1250 Kit in Silver


883 to 1212 Conversion Kits for Sportsters - Only $499.95!

For 1986-2008 Models

Want big power without spending big money? The HAMMER PERFORMANCE 883-1212 conversion kit is for you!


Send us your 883 cylinders and we'll bore them to a full 3.515" bore using our exclusive CNC boring process. We'll then hone them to a perfect fit with a set of premium quality light weight Sledge Hammer forged pistons. Rings, wrist pins, and premium quality rubber coated steel .030 head and .020 base gaskets are all included. Optionally, you can upgrade to a complete Cometic EST top end gasket set.


For the ultimate in convenience, add our pre-assembly option. We'll thoroughly clean your cylinders, precisely gap your rings, and then pre-lube and assemble the pistons and rings into the cylinders. The ready-to-install assembly will then be shipped to you in a sealed plastic bag to keep it clean and safe. This service makes the installation a breeze, as you simply lower the piston down enough in the bore to expose the wrist pin hole, position it over the connecting rod, insert the wrist pin and circlip, and push the cylinder down into position. No special ring compressor tool required!


Tech Tip: Are you converting an 883? Be sure to read our tech article on conversions for lots of good information to make your project a success!


Note: Starting in 2009, HD changed the cylinder construction and 883 cylinders can no longer be bored to 1200. If you need cylinder cores for your 2009 or later model, call us, we may have some.


Hammer Performance 883-1212 Conversion Kits for Sportsters
These kits require that you send us a serviceable pair of cylinders for boring and honing.
Cores may be available, call for availability and price

Heads

Dome Type

Compression
Ratio

Price

Add to Cart

86-Present XL883

Reverse

10:1 @49cc

$499.95

88-03 XL1200
95-96 Buell S2

Radius

10.5:1 @67cc

$499.95

98-03 XL1200S
96-03 SE/Lightning
96-98 Buell S1
97 Buell S3
97-98 Buell M2
(Lightning Heads)

10 Degree

10.5:1 @62cc

$499.95

98 Buell S1W & S3
99-02 Buell all

15 Degree

10.5:1 @67cc

$499.95

86-87 XL1100
04-present XL1200
04-present SE
04-10 Buell XB12

Rectangular

10.5:1 @62cc

$499.95

Custom Application

Flat Top

9:1 @67cc

$499.95

Race Application

30 degree x .400

Machine for
Desired CR
Note 1

$499.95

Note 1: the 30 degree x .400 dome race pistons are designed to be cut down to achieve your desired compression ratio, call for details


883-1212 Kit Options

Description

Price

Add to Cart

Gap Rings and Pre-Assemble Engine Kit

$40

Upgrade Head & Base Gasket
to Full Top End Gasket Set

$40

Select Top End Gasket Set

Tip: Choose your top end gasket set based on the type of rocker boxes you're using. The head and base gaskets all interchange from 1986-present.


Bolt-On 1050 Kits From HAMMER PERFORMANCE!

For Buell XB9 - Only $699.95

Now With Big Fin Cylinders!

1050 Kit for Buell XB9

HAMMER PERFORMANCE now has a BOLT-ON 1050cc kit for your Buell XB9! Like the 1250 kits above, this kit bolts on with no case boring required. The kit includes the same top quality components as described for our 1250 kits above: premium quality Sledge Hammer Cylinders in the proper large fin style for the Buell XB, forged 10.5:1 Sledge Hammer Pistons, rings, wrist pins & clips, and quality head and base gaskets (upgrade to a full top end set available). Pound your competition with a bolt-on 1050 kit from Hammer Performance!


Note: These kits can also be used as a high compression 1250 kit on a Buell XB12 or 2004-Up XL1200 Sportster. The compression ratio when used with a 1200 flywheel assembly and XB or 2004-Up XL1200 heads will be 12.5:1 (suitable for race gas only)


Note 2: These kits come standard with the big fin cylinders which match the XB heads. However, if you would like this kit with the 1986-2003 Xl sized fins, call us to order, we'll put together a custom kit for you.


Hammer Performance 1050 Kits for 2003-Up Buell XB9 models

Application

Dome Type

Compression
Ratio

Select Color

Buell XB9
(3.125" stroke with 7.270" rod length)

Rectangular Dome

10.5:1 @62cc

Color

1050 Kit Options

Description

Price

Add to Cart

Gap Rings and Pre-Assemble Engine Kit

$40

Upgrade Head & Base Gasket to Cometic EST Full Top End Gasket Set

$40


88 & 90 Cubic Inch Kits from HAMMER PERFORMANCE!

For 1986-present Sportsters and 2004-2010 Buell XB12 - From $970

Axtell 88 Cubic Inch Kit for Harley Davidson XL Sportster or Buell with Iron Lined Aluminum Cylinders and 30 Degree Reverse Dome Pistons
HAMMER/Axtell 88ci Kit with Iron Lined Aluminum Cylinders
Shown with 30 Degree Reverse Dome Pistons


Hammer Performance is pleased to offer 88 and 90ci kits based on AXTELL cylinders. Either kit will amaze you with arm-stretching torque and horsepower!


These kits use a stock 3.8125" stroke crankshaft and 6.926" rod length and do not change the engine height at all, so there are no issues with manifold or exhaust fit and the engine still fits in the frame. Case boring is required for installation: either kit requires the spigot holes to be opened up to 4.005" at a depth of 1.5". HAMMER PERFORMANCE can handle this critical task for you.


The 88 cubic inch kit (3.8125" bore) is offered with either iron lined aluminum or full cast iron cylinders. The 90 cubic inch kit (3.875" bore) is offered with full cast iron cylinders only as the extra strength of cast iron is needed due to the thinner construction. HAMMER PERFORMANCE highly recommends the full cast iron construction in the 88 cubic inch kit as well if you're planning to make in excess of 120 horsepower. The stock cases after boring are in danger of cracking at power levels above 120 horsepower when using an aluminum cylinder, but the cast iron cylinder adds a tremendous amount of strength to the whole assembly and we've never had a case failure when using them.


Lightweight High Performance 88ci 30 Degree Reverse Dome Forged Piston for Harley Davidsons and Buells Each kit also includes our exclusive HAMMER PERFORMANCE Sledge forged pistons, rings, lightweight tool steel wrist pins, clips, and head & base gaskets. An optional upgrade to a full top end gasket set is available for certain model years.


For street use, we recommend the flat top or 15 degree or 30 degree reverse dome kits. The flat top kits work under any of the various XL heads. The 15 and 30 degree dome reverse dome kits give the advantages of an angled squish band and require machine work on your heads to match. For race use, we recommend the 30 degree x .500 dome kit, which generally requires the domes to be machined down to provide the desired compression ratio.,/p>

Tech Tip: 30 degree domes provide the optimum angle for fuel being squeezed out of the squish band toward the flame front, and also provide the maximum unshrouding effect, reducing the shelf the air must go around to enter and exit the chamber. They are very common in race motors. Our new 30 Degree Reverse Dome piston makes this technology available for street motors as well.


For the ultimate in convenience, add our pre-assembly option. We'll thoroughly clean your cylinders, precisely gap your rings, and then pre-lube and assemble the pistons and rings into the cylinders. The ready-to-install assembly will then be shipped to you in a sealed plastic bag to keep it clean and safe. This service makes the installation a breeze, as you simply lower the piston down enough in the bore to expose the wrist pin hole, position it over the connecting rod, insert the wrist pin and circlip, and push the cylinder down into position. No special ring compressor tool required!


It's very important to order the correct cylinders for your cases from the menu below. The reason for this is the clearance cuts to accommodate the oil squirters. 1986-2003 XL's and 1995-2002 Buells have no oil squirters. 2004-Up XL's have off-center oil squirters. Buell XB models have on-center oil squirters. The cylinder spigots are notched for clearance according to the application.


Hammer Performance/Axtell 88 Cubic Inch Kits for Sportsters & Buells
Iron Lined Aluminum Cylinders

Dome Type

Compression
Ratio

Select Cylinder Finish & Engine Type

Flat Top

10.5:1 @67cc
11.25:1 @62cc
Note 1

Cylinder Type

15 Degree

10.5:1 @72cc
Note 2

Cylinder Type

30 Degree
Reverse Dome

10.5:1 @80cc
Note 2

Cylinder Type

30 Degree x .500

Mill for
desired CR
Note 3

Cylinder Type

Axtell 88 Cubic Inch Kit for Harley Davidson XL Sportster or Buell
HAMMER/Axtell 88ci Kit with Full Cast Iron Cylinders
Shown with 30 Degree Race Application Pistons


Hammer Performance/Axtell 88 & 90 Cubic Inch Kits for Sportsters & Buells
Cast Iron Cylinders

Dome Type

Compression
Ratio

Select Engine Size & Type

Flat Top

10.5:1 @67cc
11.25:1 @62cc
Note 1

15 Degree

10.5:1 @72cc
Note 2

30 Degree
Reverse Dome

10.5:1 @80cc
Note 2

Cylinder Type

30 Degree x .500

Mill for
desired CR
Note 3


Note 1: The Flat Top piston is normally chosen for a stock 62cc or 67cc chamber.

Note 2: The 15 and 30 degree reverse  dome pistons require machining a matching squish band into the chamber. HAMMER PERFORMANCE can handle this service for you. The 15 degree pistons give 10.5:1 with a 72cc chamber and the 30 degree reverse dome pistons give 10.5:1 with an 80cc chamber, which in each case is a typical size after machining the chamber to match.

Note 3: the 30 degree x .500 dome race pistons are designed to be cut down to achieve your desired compression ratio, call for details. They also require a matching squish ban to machined into the chamber.


88/90ci Kit Options

Description

Price

Add to Cart

Gap Rings and Pre-Assemble Engine Kit

$40

Upgrade Head & Base Gasket to Full Top End Gasket Set

$40

Tip: Choose your top end gasket set based on the type of rocker boxes you're using. The head and base gaskets all interchange from 1986-present.


1200 Kits From HAMMER PERFORMANCE!

For Buell XB9 - From $1200

HAMMER PERFORMANCE now has a 1200cc kit for your Buell XB9! Call us today or check back here for details.


Custom Big Bore Kits From HAMMER PERFORMANCE!

Need a special bore size not listed here? Need a custom spigot size, cylinder height, or piston compression height? HAMMER PERFORMANCE can fix you right up! We've done lots of different engine kits over the years for specific displacement classes, different fuels, and different conditions. We have the experience and knowledge to make your project a success, and we can work with the various vendors of cylinders, pistons, and rods to put together the combination that works for you. Call us today!

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