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Top End Components

Unlock the hidden potential of your engine with powerful Top End upgrades from Zipper’s Performance Products. Zipper’s Performance keeps specially CNC-machined heads in stock for super-quick turnaround (on an exchange basis) for Twin Cam® and Sportster® engines. Twin Cam® big bore cylinder conversions for 88 to 95” and 98″ plus 96 to 103” and 107″ fitted with forged pistons in many different compression ratios for fast turnaround or exchange. Zipper’s Performance also stocks pistons, valves, guides, valve spring kits, and other critical top end parts from the industry’s most renowned manufacturers.

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Zipper's Milwaukee-Eight® Exchange Cylinder Kits

Zipper’s Milwaukee-Eight® Big Bore Cylinder Kits

Zipper's
$0.00
Increasing the size of a Milwaukee-Eight® engine is easy with Zipper’s Big Bore Cylinder Kits. Milwaukee-Eight® engines respond to displacement increases like no other HD engine! Factory stock, the 4-valve head flows a lot of air so making the engine bigger rewards the rider with huge torque and horsepower gains. Our kits include new cylinders that drop right on the factory case for like-stock installation. 4.125 and 4.250 Bores Zipper’s offers new big bore castings with bore sizes from 4.125 to 4.250. These castings are more durable than the O.E. units with the following features
  • New Design Cast Aluminum Alloy for Strength and Reliability
  • Stress Relieved Iron Liners
  • Precision Sized by Zipper’s with the most Advanced Processes
  • Special Ring Packs for Advanced Cylinder Sealing
  • Gasket Surface Finish Improved for Superior Seal using Cometic MLS Gaskets
  • Zipper’s Forged "Spec Built" Pistons manufactured by CP
We have dome configurations for all bore sizes that will drop on any H-D 107, 114 or 117 H-D engine. The dome volumes are for OE or SE M8 heads or larger valve heads with increase chamber size with compression up to approx. 11:1    4.125 X 4.375 stroke = 117ci    4.125 x 4.500 stroke = 120ci    4.250 x 4.375 stroke = 124ci    4.250 x 4.500 stroke = 128ci Kits include fitted cylinders, pistons with rings, pins & clips, head and base gaskets and new head bolts. The rings custom sized to each cylinder. In compliance with ARB emissions laws, this product is not sold or shipped to California.  
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Zipper's Muscle 124" Kit for 2017-2019 107" Milwaukee-Eight® Models

Zipper’s Muscle 124″ Kit for 2017-2019 107″ Milwaukee-Eight® Models

Zipper's
$0.00
Zipper's Muscle 124" Kit for the 107" M-8 is the most powerful top end and cam kit we've ever produced for a production motorcycle! The big breathing 4-valve heads on the M-8 engine just love displacement, so we've developed this kit for use with our new 4.250" bore drop-on cylinder. These cylinders are fitted with flat-top forged pistons and topped off with Zipper's Stage III CNC headwork performed on your cores. Our Red Shift 552 cam delivers HUGE torque as soon as you open the throttle, and carries it across the RPM range to provide instant acceleration from any RPM. Scroll down to read more! Requires your heads to be provided for modification. Exchange parts may be available – Contact us for availability In compliance with ARB emissions laws, this product is not sold or shipped to California.
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Zipper's Muscle 124" Kit for 2017-2019 107" Milwaukee-Eight® Models

Zipper’s Muscle 128″ Kit for 2017-2019 114 & 117″ Milwaukee-Eight® Models

$0.00
Zipper's Muscle 128" Kit for the 114-117" M-8 is the most powerful top end and cam kit we've ever produced for a production motorcycle! The big breathing 4-valve heads on the M-8 engine just love displacement, so we've developed this kit for use with our new 4.250" bore drop-on cylinder. These cylinders are fitted with flat-top forged pistons and topped off with Zipper's Stage III CNC headwork performed on your cores. Our Red Shift 552 cam delivers HUGE torque as soon as you open the throttle, and carries it across the RPM range to provide instant acceleration from any RPM. Scroll down to read more! Requires your heads to be provided for modification. Exchange parts may be available – Contact us for availability In compliance with ARB emissions laws, this product is not sold or shipped to California.
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Zipper's Muscle 117" Kit for 2017-2019 107" Milwaukee-Eight® Models

Zipper’s Muscle 117″ Kit for 2017-2019 107″ Milwaukee-Eight® Models

Zipper's
$0.00
Our Muscle 117" Kit for the M-8 platform creates phenomenal power in a bolt-on top end and cam kit! We precision-bore and hone your cylinders to accept our +6cc domed pistons and then CNC-port your heads for increased flow and minimize intake to exhaust port differential. Oversize valves and performance valve springs are installed on carefully machined heads that are key to making this big M-8 power. We offer this kit with 2 cam choices, both of which deliver excellent power curves that are sure to satisfy any aggressive rider. The High Torque kit includes a Red Shift 548 cam - this is what we call the "rowdy" choice. The 548 creates tire-shredding power from just about any part-throttle RPM. Great for rowdy riders wanting instant power that are channeling their hooligan spirit animal! The High Power kit (Red Shift 552) builds power with an extra-strong mid-range and top end pull. This is the one for power junkies who regularly run in higher RPM ranges and want max available power. Both cams have a very lopey sound & feel–no hiding that this is a not stock engine! These kits include gaskets, tappet cuffs and a set of Quickee pushrods with covers to simplify reassembly. An EFI tuner, performance exhaust, oversize throttle body, injectors-intake will be required to achieve results shown In compliance with ARB emissions laws, this product is not sold or shipped to California.
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Zipper's Sleeper 117" Kit for 2017-up 107" Milwaukee-Eight® Models

Zipper’s Sleeper 117″ Kit for 2017-up 107″ Milwaukee-Eight® Models

Zipper's
$0.00
"Sleep-er" (slang) A vehicle which has been internally modified while retaining a mostly stock appearance in order to fool opponents in a drag race, or to avoid the attention of the police. This powerful kit by Zipper's transforms your 3.937" bore 107" M8-powered machine to 4.125" bore 117" with a simple piston swap in your provided cylinders. We first remove the dowels from the cylinders and machine the head gasket decks to ensure flatness and proper finish for positive MLS head gasket seal. The cylinders are then treated to the best precision boring and honing process you can find, as our technicians precisely measure each piston to provide skilled, old-fashioned sizing processes to the cylinders. Mounted in special torque plates, a CNC-hone is used to create a straight and true finish, topped off with brush-finish technology that requires minimal run time for ring seating while providing best power. Choose the Red Shift cam (468 Early Torque or 472 Balanced Power) that will provide the power output that best matches your riding style and we'll package it up with a new full compliment cam bearing, top end-cam chest gasket set along with a set of Quickee pushrods and covers to simplify reassembly. This is a hugely cost-effective way to increase the power of the Milwaukee-Eight® engine – with stock heads! In compliance with ARB emissions laws, this product is not sold or shipped to California.
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Zipper's 107 to 117" Big Bore Pistons For Milwaukee-Eight® Engines

Zipper’s 107 to 117″ Big Bore Pistons For Milwaukee-Eight® Engines

Zipper's
$0.00
Turn your 107" M8 engine into a 117" by simply boring your stock cylinders! No case modifications necessary, the factory 107" can be safely bored from 3.937" to 4.125". These forged pistons are manufactured for us by CP-Carrillo in 3 different compression ratios (flat top compression ratio is 11.2:1 with an unmodified 87.5cc head) and feature 1.5mm compression rings with 3mm oil rings for superior oil control. Piston kits include pistons, rings, wrist pins and circlips. USA made! In compliance with ARB emissions laws, this product is not sold or shipped to California.
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