Hammer Performance - for All Your Harley Davidson XL Sportster and Big Twin Performance Needs
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For Sportster & Buell

At HAMMER PERFORMANCE, we have the finest Top End components available for your Sportster or Buell!

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Sledge Hammer Pistons

Hammer Performance is proud to offer our exclusive SLEDGE HAMMER pistons! $309.95/set

High Performance Sledge Hammer Pistons for Harley Davidson XL Sportster and Buell Models

Years of research into high performance piston technology has resulted in what we believe to be the finest high performance pistons available for your Sportster or Buell. Precision machined from the latest lightweight 2618T-61 forgings, our pistons feature:

  • Extra large valve pockets for those high-overlap cams
  • Anti-detonation grooves around the crown to disrupt detonation waves and limit contact
  • Ribbed design for more strength with less weight
  • Dual wrist pin oilers
  • Expansion grooves for better ring seal
  • Extra-strong pin bosses with short lightweight tool steel wrist pins

Each set includes two pistons, rings, pins, and circlips.

NEW! Sledge Hammer 30 Degree Reverse Dome Pistons!

30 Degree Reverse Dome Pistons for Harley Davidson XL Sportster Models

When it comes to making power, the 30 degree dome angle has always been the best arrangement. The 30 degree angle provides maximum unshrouding, 30 Degree Reverse Dome Piston for for Harley Davidson XL Sportster and Buell Models reducing the shelf the air must go around to enter or exit the chamber, and it also directs the fuel coming out of the squish band more directly at the flame front resulting in better efficiency.

But the trade-off has always been a reduction in squish band surface area for a given dome height. To get enough squish band, the dome has to be made extra tall, raising the compression ratio beyond what pump gas can support. For this reason, 30 degree dome angles have primarily been limited to race motors.

Well now, HAMMER PERFORMANCE has solved that problem! Our new 30 degree reverse dome pistons have a tall dome to provide plenty of squish area, but they also incorporate a dish in the middle, lowering the compression ratio to pump gas friendly levels. The dish also creates a spherical shaped burn area, a proven horsepower producing shape. They also include all of the other great features of Sledge Hammer pistons as described above. This is a no compromise piston design that makes big power!

Available in 3.563, 3.813, and 3.875 bore. Chamber machining is required for 30 degree pistons ... HAMMER PERFORMANCE can handle this service for you.

Tech Tip: XL and Buell heads have been offered with a variety of different chamber sizes and shapes. It's extremely important to select the correct dome configuration to match your cylinder heads and desired compression ratio. If you're unsure about the type of cylinder heads you have or the correct piston for your application, don't hesitate to call us. Also, you may find the answer by reading our tech article on XL cylinder heads.

Bore Size


Select Dome Type







High Performance 1250cc Kit Sledge Hammer Pistons for Harley Davidson XL Sportster and Buell Models
Ultra Lightweight and Super-Strong SLEDGE HAMMER Pistons from HAMMER PERFORMANCE

The Underside of a Lightweight High Performance Sledge Hammer Piston for Harley Davidson XL Sportster and Buell Models
Sledge Hammer Pistons are ribbed for more strength and less weight
The pin bosses are designed extra strong to allow a short, lightweight pin as well
We believe these are the finest HD/Buell performance pistons on the market

So Just How Much Lighter is a Sledge Hammer Piston?

Weight of the competition's 1250 kit piston and pin Weight of the HAMMER PERFORMANCE 1250 kit piston and pin

Here's a side by side comparison of a conventional forging 1250 kit flat top piston and the SLEDGE HAMMER 1250 kit flat top piston. That's a whopping 57 gram difference, giving a total savings of 114 grams of reciprocating weight with two pistons! Less weight means less vibration, less wear and tear on the lower end, and more power!. Use the best, SLEDGE HAMMER pistons from HAMMER PERFORMANCE!

Sledge Hammer Cylinders

Bolt-On 1250cc Cylinders from HAMMER PERFORMANCE - $400/Set

Now Available in the 2004-Up Large Fin Style!

High Performance 1250 Kit Cylinders for Harley Davidson XL Sportster and Buell Models

Sledge Hammer 1250 cylinders from Hammer Performance are the result of over a decade of experience with 1250 kits. We've seen what works and what doesn't, and none of the offerings on the market really solved all the issues we came across, so we set out to make a cylinder that combines the best features of all of them. We're proud to bring you these fine cylinders, which we believe to be the best ones available for a street 1250 application.

Ring seal depends on a straight and round bore, and this is the main objective in any cylinder design. Under the extreme pressure and heat of a high performance engine, cylinders want to grow, twist and distort, and that makes it impossible for the rings to stay sealed. We've seen some cylinders that grow and distort so badly that head bolts break, cylinder studs pull out of the cases, and head gaskets blow.

High Performance 1250cc Kit Cylinders for Harley Davidson XL Sportster and Buell Models

For the straightest and roundest bore possible under these extreme conditions, cast iron is the ticket, as it's much stronger and grows about half as much as aluminum. But aluminum offers advantages in the form of reduced weight, better heat dissipation, and it doesn't rust. So we made Sledge Hammer 1250 cylinders with the best of both worlds: an aluminum cylinder with an extra thick iron liner that stays straight and true. The end result for you is a lightweight, cool cylinder with superb ring seal for less oil consumption, less blow-by, and more power


But we didn't stop there. Since the cylinder stays round and true, ring seal depends less on the ring's ability to carve the liner into it's shape. As a result, were were able to use a harder iron alloy for the liner than you find in most cylinders - we actually had to get new, harder honing stones to even hone these cylinders! Our measurements show a wear rate that's less than half the wear rate on the factory cylinders. You can expect a long, trouble-free life from Sledge Hammer cylinders.

Sledge Hammer 1250 Cylinders are available in three different finishes: Silver, Black, and Black with Highlighted fins. They are designed for a 3.563" final bore size after honing to fit. Hammer Performance can handle this service for you so long as we have the pistons available. We offer our premium Sledge Hammer forged pistons, or if you have your own pistons, send them to us for fitment.



Select Year & Color

Sledge Hammer Cylinders - Pair
(must be honed to fit)


Hone Cylinders and Fit Pistons - Pair
(send us your pistons or
purchase new Sledge Hammer pistons)


Axtell Cylinders

Big Bore Cylinders from the Biggest Name in the Business

Hammer Performance is proud to carry Axtell cylinders, the biggest name in cylinders for Harley Davidson applications.

The Axtell Full Cast Iron XL Cylinder

For the ultimate in bore stability and ring seal, the Axtell full cast iron XL cylinder can't be beat! We use these fine cylinders on our own race bikes as well as severe duty street bikes.

High Performance Axtell Cast Iron Cylinder for Harley Davidson XL Sportster and Buell Models

These cylinders are particularly well suited to high horsepower applications where the cases have been bored. Boring an XL case weakens it and we've seen them crack many times when the horsepower levels get over 120. However, Axtell full cast iron cylinders add strength and stability to the engine cases. We have yet to crack a single set of cases when using these cylinders, which is why you find them on all of our race motors.

We can provide these cylinders in any bore size from 3.5" to 3.875", as well as any spigot diameter from stock to 4". Taller or shorter versions are available as well for those special projects. Call us to discuss your project and we'll make sure you get the exact configuration you need.

The Axtell Iron Lined Aluminum XL Cylinder

These cylinders are the foundation of a great big-bore street motor! They combine an extra-thick iron liner for bore stability and ring seal with aluminum fins for heat dissipation and reduced weight. We use these on many XL and Buell big bore projects with great success.

We can provide these cylinders in any bore size from 3.5" to 3.813", as well as any spigot diameter from stock to 4". Taller or shorter versions are available as well for those special projects. Call us to discuss your project and we'll make sure you get the exact configuration you need.

Cylinder Heads

High Performance Factory Heads are Available from HAMMER PERFORMANCE!

HD has offered a lot of heads for XL & Buell models over the years, some good and some not-so-good. If you're looking to upgrade to the best ones, Hammer Performance can set you up. We offer factory performance heads either as bare castings with stock seats and guides (which make a great basis for your Smash or Sledge porting service), or fully assembled and ready to bolt-on.

Buell Thunderstorm Heads - No Longer Available

High Performance Thunderstorm Heads for Harley Davidson XL Sportster and Buell Models

As of July 2013, we're having trouble sourcing new Thunderstorm heads. The last bikes that had them rolled off the assembly line 11 years ago, so this is no big surprise. We'll leave the information below for reference purposes, but we can no longer supply new Thunderstorm heads

Buell Thunderstorm heads were the first real performance head for XL's offered by the motor company. They came out in 1998 on Buell S1W and S3 models, and instantly became enormously popular as an upgrade for XL's and other Buells.

The improvements over the previous XL heads came in the form of much larger valves, improved ports, and an improved chamber. Valve sizes were increased from the earlier 1.715" intake & 1.480" exhaust all the way up to 1.810" intake & 1.575" exhaust. This alone results in dramatically better flow. But the ports were improved as well, with a higher floor and a more gradual radius in the roof through the bowl area. Finally, the chamber was improved to add a 15 degree squish band while not shrouding the valves terribly, and the heads were paired with an all new matching piston. Squish band effectiveness is limited, however, by the cast-in squish shelf, which is uneven and not very accurate. Hammer Performance can machine this area for a precise and effective squish band.

Retrofitting these heads to 91-03 Sportster models is very straightforward, as they are almost a bolt-on. The only issue is that the front head's front mount bolts are 7/16-14 thread, instead of the 3/8-16 as found on 91-03 Sportsters. Some drilling of your front motor mount bracket will likely be necessary, and you'll need to fit a short stud onto the left side (spark plug side) or use a very short bolt.

Retrofitting these heads to 86-90 Sportster models is not recommended, however, plenty of people have done it. The main issue is the spacing of the pushrod holes. Four-speeds have slightly different geometry because the tappets are offset from the cams slightly. When you put five speed heads onto a four speed, you risk causing a pushrod rub problem where the pushrods pass through the heads. The same bolt hole size issue described above also exists when retrofitting these to four-speeds.

Retrofitting these heads to 04-up Sportster models is recommended even less. First off, if your 04-up Sportster is a 1200, you already have better heads than these, so swapping them would be a downgrade. But even if you're looking for something better than your 883 heads, Thunderstorms are generally not the best choice for an 04-Up. Thunderstorm heads have smaller fins than the 04-Up Sportster head & cylinder fins, and they may look funny sitting over the top of your late model cylinders. Also, the front head's right front mount hole (pushrod side) sits 1/4" more outboard on a Thunderstorm head than on a late model XL head, so a mount modification would be needed. It's not impossible to put these on a late model XL, but most people opt for the Buell XB or late model XL1200 heads instead.

Thunderstorm heads are available in a straight black finish only. The fins can be highlighted manually but this seldom comes out looking as good as a factory highlighted fin. If you're looking for highlighted fins, we recommend going with some 2004-Up XL1200 heads as listed below. If you're looking for silver, you can either paint a set of Thunderstorms, or go with a set of XB heads listed below. You could strip and powder coat a set of Thunderstorms, but by the time you got done, you'd be into them about as much as a set of XB heads.

Thunderstorm heads are available from HD either bare or fully assembled. However, as of their latest price increases, they're charging the same amount either way. Therefore we are only offering them in assembled form.

Despite the introduction of the Buell XB and 2004-Up XL1200 heads, Thunderstorms remain popular. The bikes that Thunderstorms came on as original equipment are long out of production, though, in fact Buell doesn't even exist anymore, so who knows how long these heads will be available. If you want a set, get them while you can.

Buell XB & 2004-Up XL1200 Heads

High Performance XB Cylinder Heads for Harley Davidson XL Sportster and Buell Models

The best factory heads for high performance are the 2003-Up Buell XB and 2004-Up XL1200 heads. These heads feature improved ports over any of the previous factory heads, with large 1.810" intake and 1.575" exhaust valves featuring lightweight 7mm stems and a beehive spring pack that can handle up to .550 lift (previous XL heads were only safe to .500 lift). Although they flow about the same as the Thunderstorm heads, they do it with a smaller port and the flow is less turbulent, both of which result in more power. In our testing, comparing stock to stock, these heads are worth 4-5 extra horsepower over Thunderstorm heads, in situations where the heads are the thing limiting the power. Stock Thunderstorm heads start becoming a big bottleneck at around 90hp and these heads in stock form start becoming a bottleneck at closer to 95hp.

Another improvement in these heads over the Thunderstorms is the compact 62cc bathtub chamber. This chamber gives a nice, even squish area when used over flat top pistons (for a 9.7:1 compression ratio) or our premium rectangular dome Sledge Hammer forged pistons (for a 10.5:1 compression ratio). They also provide plenty of material for machining angled squish bands, which improves performance even more by reducing the shelf the air must flow around when entering and exiting the cylinder, as well as by directing the fuel coming out of the squish band more directly at the flame front. Hammer Performance offers both 15 and 30 degree angle dome Sledge Hammer forged pistons and can CNC machine the heads to match. These heads work especially well with our 30 degree reverse dome pistons described above.

Be aware that there was a significant change beginning in 2007 when the factory went to fuel injection on the Sportsters. 2007 and newer XL heads have their manifold mating surface milled down about .062" versus the carburetor heads, and also they have the manifold flange bolts moved apart to accommodate the larger EFI throttle body, with wider manifold flanges to match.

The 2006 and earlier earlier XL heads, made for a carb manifold, cannot be used with an EFI throttle body without significant machine work. The 2007-up heads however can be used with a carburetor by using a special wider intake manifold available from HAMMER PERFORMANCE.

Recently some of the replacement carb style heads from HD have been coming with the wider bolt spacing to match the EFI style manifold flanges. However, the manifold surfaces have not been milled down and a standard carb manifold still fits fine.
High Performance XB Cylinder Heads for Harley Davidson XL Sportster and Buell Models in Black
Buell XB heads have manifold surfaces for a carb type intake manifold, so they cannot be used with the XL's EFI throttle body. The black versions however use the new style manifold flanges, so be sure to pck up a pair of flanges if you don't already have them.

Also, be aware that Buell XB heads as delivered do not have the breather bolt/carb mount holes drilled and tapped. However, if you buy the heads from HAMMER PERFORMANCE and let us know you'll be using them with a carburetor, we will machine and tap the holes for you for no charge. This is one advantage to buying these heads from HAMMER PERFORMANCE.

Since all Buells are now out of production, we can't be sure how much longer XB heads will be available. If you're thinking about getting a set, this might be the time.

Which Heads to Choose?

Use this guide to help choose which heads are right for your bike:

Carburetor Fuel Injection
Silver Buell XB
in Silver
Black Buell XB
in Black
See Note 2
2007-Up XL1200
in Black
Black with
Highlighted Fins
2004-2006 XL1200
See Note 1
2007-Up XL1200
in Black Highlighted

Note 1: The EFI heads will also work in this application when combined with a special wider intake manifold available here.

Retrofitting late model heads to 91-03 XL models is not difficult and many people have done it with great results. As with the Thunderstorm heads, you have to deal with the larger 7/16-14 front mount bolts. You also need to deal with the fact that the right front mount bolt is relocated inward 1/4", but this is easily resolved with an inexpensive front mount available below. Also, be aware that your head fins will overhang the cylinder fins somewhat, although most people don't find it objectionable. Finally, be aware that these heads are .020" shorter than stock 91-03 heads, which by itself should not cause an issue. However, if you're lowering your stack further with head milling and/or thin gaskets, you need to factor this in when considering pushrod length. Read more about pushrod length considerations here.

Retrofitting these heads to 86-90 (four speed) models is not recommended for the same reasons cited above for Thunderstorm heads, primarily the valvetrain geometry and the potential for pushrod rub issues.

These heads are not available from the factory in an assembled form, you must buy the heads and all the componentry separate and do the assembly yourself. However, Hammer Performance will sell you the heads completely assembled and ready to install for the same price as all of the pieces cost when buying from your dealer. We'll even upgrade the valves to a set of our premium quality stainless steel swirl polished Sledge Hammer valves at no extra charge!

Buell XB Heads - Pair
Buell XB Heads - Pair
Note: wider manifold flanges required, order below
2004-2006 Sportster 1200 Heads - Pair
Black with Highlighted Fins
2007-Up Sportster 1200 Heads - Pair
Black with Highlighted Fins
2007-Up Sportster 1200 Heads - Pair
All Black
Intake Manifold Flanges - $15.98/Pair
for 2007-Up Sportster Heads
Front Mount Bracket - $18.99
(to Adapt XB/04-Up XL1200 heads to 86-03 Models)
Machine Angled Squish Band
and Size Chamber - $130/Pair

Specify Dome Angle and Chamber Size:

Machine/Drill/Tap XB Head Breather Bolt Holes

Billet Motor Mounts for Buells - From $160

Billet Front Motor Mount for 1995-2002 Buells
Billet Motor Mount for 1995-2002 Buell Twins
Billet Front Motor Mount for Buell Blast Models
Billet Motor Mount for Buell Blast Models

Strong and Beautiful - Available for XL or XB style Heads

These billet motor mounts are precision CNC machined from a solid chunk of 6061T6 aluminum billet. They replace the failure-prone factory mount and look beautiful in the process. Available to fit the standard bolt spacing found on 1986-2003 XL and 1995-2002 Buell heads, as well as the narrower bolt spacing found on Buell XB and 2004-newer XL heads.

Billet Motor Mounts for Buells



Add to Cart

Billet Motor Mount
For 1995-2002 Buell Models (except Blast)
Note: Using this mount on S2 models with the stock front head requires a sleeve for the pushrod side bolt, if the 3/8" bolt is retained
Note 2: factory original isolators used a 1/2" bolt
current service replacement isolator kits come with a 7/16" bolt
choose the hole size desired


Choose type of heads
Top Hole Size

Billet Motor Mount Only
For Buell Blast Models - All Years


Choose type of head

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