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

For Sportster & Buell

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INTRODUCING BOLT-ON 1275 Kits from HAMMER PERFORMANCE

For 1986-present 883 & 1200cc Sportsters and Buell - From $649.95

Black Highlighted 2004-Present 1275 Kit for Harley Davidson XL Sportster or Buell
Click on the Image Above for a Slide Show of 1275 Available Colors and Fin Styles



HAMMER PERFORMANCE RAISES THE BAR AGAIN! We're pleased to announce the world's first and only BOLT-ON 1275 KITS for the XL platform! These kits stand alone as the biggest XL engine kit available that can be installed in an afternoon without case boring and without removing your engine from the frame.

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


Features and Benefits


First on the list is our innovative new cylinder design!

HAMMER PERFORMANCE bolt-on 1275 cylinder spigot Harley Davidson XL Sportster
The 120,000psi Tensile Strength Steel Liner Enables a Thin Spigot for a Bigger Bore

HAMMER PERFORMANCE bolt-on 1275 cylinder liner Harley Davidson XL Sportster
The Working Area of the Liner Remains Thick to Promote a Straight, Round Bore that Doesn't Distort Under the Heat and Pressure of a Running Engine. This Results in Superb Ring Seal.


The 1275 cylinder is based heavily on our legendary 1250 kit, with one key difference: the liner is made of special 120,000 psi tensile strength steel. This extra strong liner material enables a thinner spigot, which in turn enables the bigger bore. The working area of the cylinder remains at a full four inches outside diameter, maintaining the thick, strong cylinder wall. As a result, this cylinder delivers superb ring seal in even the most highly stressed, demanding applications, enabling more power!.

So how much power is it capable of supporting? Take a look at this actual result achieved in our testing:

Dyno Sheet for 132 horsepower 1275cc Sportster
Actual Result From our 2007 XL883/1275 Sportster With the 120+ Horsepower Package


Our very first prototype 1275 kit delivered this dyno result in it's first test, when combined with the other components of the 120+ horsepower package. We also tested these cylinders for nearly a year in some of the most demanding street and drag race applications. The 1275 cylinder performed flawlessly! The new liner has proven itself and the time for testing is over, it's now time to make these available to the general public!

As with the 1250 kit, the 1275 kit is available in either the 1986-2003 small fin or 2004+ big fin style:

Small Fin 1986-2003 1275 Cylinder and Big Fin 2004-present 1275 Cylinder for Harley Davidson XL Sportster or Buell


You can see what a massive difference in fin sizes this represents! HD introduced big fins in 2004 when the cylinder pressure in 1200's was raised dramatically. The larger fins were part of a coordinated plan to improve the cooling of the motor to handle the additional heat, along with oil squirters under the pistons and MAP based ignition. Don't compromise the cooling or appearance of your motor - use big fin cylinders on 2004+ bikes!. Big fin cylinders will also fit on 1986-2003 bikes. We offer the 86-03 small fin style as well, so that owners of that year range can maintain the proper appearance.

Also notice the CNC highlighted fins in the above photo!

CNC machining fin edges on HAMMER 1275 kit cylinders for Harley Davidson Sportsters and Buells


We don't sand fin edges! All black highlighted HAMMER 1275 cylinders, big fin or small fin, receive the CNC machined fin edge treatment. If you're going for the black highlighted look, there's no need to settle for the sanded fin edges found on some competing 1250 kits. HAMMER 1275 cylinders match the factory fin highlighting on 1200 models and maintain your engine's beautiful appearance!

And finally, all HAMMER 1275 kits utilize high-end "X-Forging" pistons that are proven to be the lightest and strongest forged piston design you can buy:

Lightweight High Performance 1275cc 30 Degree Reverse Dome Forged Piston for Harley Davidsons and Buells


The ribbed design results in a stronger piston with less weight, which results in more power, less vibration, and less wear and tear on the lower end. They also feature extra large valve pockets for those radical cams, anti-detonation grooves, dual wrist pin oilers, expansion grooves for superior ring seal, ribbing to give maximum strength with minimum weight, and of course our exclusive 30 degree reverse dome designs that deliver maximum valve unshrouding and superb detonation resistance. Don't settle for standard forged pistons, get the BEST pistons money can buy for your HD or Buell!.


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 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 1275 KIT FROM HAMMER PERFORMANCE TODAY!

Hammer Performance 1275 Kits for Sportsters & Buells

Heads

Select Details

86-Present XL883
Note: the pistons in these kits
have valve pocket placement that
works with 883 heads only

Fin Style
Color
Pistons
Specific Year of the Motor

88+ XL1200
86-87 XL1100
88-10 Buell 1200

Fin Style
Color
Pistons
Specific Year of the Motor


Note 1: 30 degree pistons require machine work in the chambers to size and shape them appropriately.
HAMMER PERFORMANCE can handle this service for you.
Note 2: the 30 degree x .500 dome race pistons are designed to be cut down to achieve your desired compression ratio, call for details


BOLT-ON 1250 Kits from HAMMER PERFORMANCE

For 1986-present 883 & 1200cc Sportsters and Buell
CLOSEOUT PRICED - From $549.95

Black Highlighted 2004-Present 1275 Kit for Harley Davidson XL Sportster or Buell
Click on the Image Above for a Slide Show of 1250 Available Colors and Fin Styles



The legendary HAMMER 1250 Kit is a bolt-on that can be installed in an afternoon without case boring and without removing your engine from the frame. Now with a new low closeout price! We're closing out these kits for all applications except the basic 883-1250 conversion. We are not restocking any of the other 1250 pistons and will be moving all of those applications to the 1275. As we run out of each of the piston choices, we will remove them from the below ordering table. Get yours while it's still available!

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


What Makes HAMMER 1250 Kits the Best?

Several things! Let's start with the Sledge Hammer 1250 cylinders, which feature an extra heavy duty iron liner and aluminum fin construction:

Small Fin 1986-2003 1250 Cylinder and Big Fin 2004+ 1250 Cylinder for Harley Davidson XL Sportster or Buell


Why a thick liner? A thick liner promotes a straight, round bore under the heat and stress of a running motor. This provides superb ring seal. The iron liner material is also rock hard for a long, trouble free life, and the aluminum fins promote excellent heat dissipation. Iron lined aluminum is the proven best cylinder construction for street ridden bikes, without the streaking issues of nikasil or the heat and weight issues of full cast iron construction, and we believe the HAMMER 1250 cylinder is the best iron lined 1250 cylinder on the market. There are thousands and thousands of these cylinders in service, in bikes all over the world, making great power and performing flawlessly. You cannot buy a finer cylinder!

In addition to the superior construction, these are the ONLY 1250 cylinders available in the 2004+ big fin style! See the picture above. Other companies ask you to put the 1986-2003 small fin cylinders onto your 2004+ bike. And yes, they can be made to fit the late model bikes by grinding on the lowest fin. But that's a hack! And on top of that, you'll reduce the cooling capacity of your motor. Big fins came out in 2004 for a reason; cylinder pressures on the 1200 models were raised dramatically starting in 2004. Big fins were part of a coordinated plan to manage the additional heat. Other things that were done were MAP based ignition and oil jets to cool the undersides of the piston domes. Head fin sizes were changed at the same time, and using small fin cylinders causes an appearance mismatch. It's just an all around bad plan. Don't go backwards in cooling capacity or appearance - use SLEDGE HAMMER CYLINDERS from HAMMER PERFORMANCE!

And finally, if you've got the black highlighted look on your bike, there's yet another compelling reason to choose SLEDGE HAMMER cylinders:

Sanded fin edges versus machined fin edges on 1250 cylinders for Harley Davidson Sportsters and Buells


One of our competitors doesn't even offer cylinders with highlighted fins. Another of our competitors just hits them with a sander resulting in the product you see on the left in the above picture. HAMMER PERFORMANCE takes the extra time and trouble to CNC machine the fin edges as shown on the right above. This properly matches the factory black highlighted cylinder heads. We do this for both small fin and big fin cylinders at no extra cost to you.

HAMMER PERFORMANCE Black Highlighted Big Fin 1250 kit for 2004+ Harley Davidson Sportsters and Buells
HAMMER 1250 Kits Offer Superior Appearance and Superior Cooling
Don't Settle for Less!


We'd show our big fin black highlighted cylinders next to the competition's offering, but no one else even offers big fin 1250 cylinders!

Lightweight High Performance 1250cc 30 Degree Reverse Dome Forged Piston for Harley Davidsons and Buells We also have the best 1250 pistons on the market! 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!




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 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!


NOTICE: We are currently out of stock on black and black highlighted 1250 cylinders, both big and small fin. This is a temporary condition, check back for availablity. Or better yet, upgrade to one of our 1275 kits!

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

Hammer Performance 1250 Kits for Sportsters & Buells

Heads

Select Details

86-Present XL883
Note: the pistons in these kits
have valve pocket placement that
works with 883 heads only

Fin Style
Color
Pistons
Specific Year of the Motor

88+ XL1200
86-87 XL1100
88-10 Buell 1200

Fin Style
Color
Pistons
Specific Year of the Motor


Note 1: 30 degree pistons require machine work in the chambers to size and shape them appropriately. HAMMER PERFORMANCE can handle this service for you.
Note 2: the 30 degree x .500 dome race pistons are designed to be cut down to achieve your desired compression ratio, call for details


1250 & 1275 Kit Options

Depending on the year of your bike, other components are necessary for a successful 1250 or 1275 conversion. Specifically:

Although these items may be found elsewhere on the site, we have included them in the table below for convenience. Or, see our Performance Packages below for complete packages with everything you need to achieve your desired power level.


1250 & 1275 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 - Recommended for 86-03 models, Required for all 04-06 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 91-93
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.


1250 & 1275 Kit Performance Packages


This section is being revamped, please check back again soon!

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.


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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