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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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  1. Be the first to review this product

    As low as: $779.95

    Want to increase the size of your Milwaukee-Eight® engine? Zipper's offers precisely machined H-D® cylinders fitted with big bore pistons using expert processes we have developed since 1981 that guarantee a perfect seal. Starting with a "seasoned" H-D® cylinder casting, we ensure that the MLS gaskets we supply will adhere and seal by removing the dowels and turning the cylinder tops on a specially tooled lathe for flatness, surface finish and perpendicularity. The bores are machined for larger pistons, then diamond honed on torque plates to a clearance dimension determined by carefully measuring each piston for accuracy. Our final finish process speeds break-in and provides a superior ring seal. These kits are supplied with our proprietary CP forged piston kits that include standard tension 3mm oil rings for excellent oil control and longevity. Cometic head and base gaskets are supplied for assembly. This service is provided to your cylinder cores; in most cases a refundable core deposit can be charged to ship finished parts ahead of your parts arriving. If you're interested in purchasing cylinder cores outright (no exchange), please contact our sales department. In compliance with ARB emissions laws, this product is not sold or shipped to California.
  2. Be the first to review this product

    From: $1,395.00

    To: $2,790.00

    "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.

  3. Be the first to review this product

    From: $989.95

    To: $8,237.90

    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.

  4. Be the first to review this product

    From: $374.95

    To: $1,124.85

    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.

  5. Be the first to review this product

    As low as: $1,799.00

    The 4-valve M8 cylinder head flows considerably more air than previous 2-valve heads – but it needs to, to support today's larger engines. Flow testing the stock heads shows an imbalance between intake and exhaust flow ratios. Our combination of qualifying seat installation, CNC porting, professional seat and guide finishing with oversize valves, careful spring set up and decking ensures you will extract maximum power from your engine modifications while improving the flow imbalance. This work is performed on your supplied head cores. In compliance with ARB emissions laws, this product is not sold or shipped to California.
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