# Zippers Performance: Aftermarket Parts for your Harley > Zipper's Performance is an industry award\-winning Manufacturer and Distributor of aftermarket Harley\-Davidson performance parts\. Generated by Yoast SEO v28.2, this is an llms.txt file, meant for consumption by LLMs. ## Pages - [Zipper's Employment Opportunities](https://www.zippersperformance.com/employment/) - [Zipper's Manufacturing CNC DEPARTMENT](https://www.zippersperformance.com/cnc-department/) - [Downloads](https://www.zippersperformance.com/downloads/) - [Zipper’s Technical Sales](https://www.zippersperformance.com/zippers-technical-sales/) - [WAREHOUSE DEPARTMENT](https://www.zippersperformance.com/warehouse-department/) ## Products - [Inner Primary Bearing Upgrade](https://www.zippersperformance.com/bearing-upgrade/): In high output applications, we’ve seen the primary bearing race on 1985\-2006 models that is pressed onto the main shaft walk in to the main drive gear and damage it, requiring expensive repairs\. This unit replaces the two\-piece H\-D® bearing with a single sealed unit, similar to the earlier model bearing used successfully for years\. Requires the seal listed below for wet applications\. Fits all 1985\-2006 Big Twins; requires \# 872\-527 seal and original equipment bearing and race removal\. \\ \\ - [ThunderMax® With AutoTune For 2004\-2016 Dyna® Models®](https://www.zippersperformance.com/thundermaxr-with-autotune-for-dynar-modelsr/): ThunderMax® is an industry award winning, performance ECM designed specifically for EFI equipped Harley Davidson® motorcycles\. This highly advanced, stand\-alone tuning system utilizes proprietary AutoTune technology specificly designed to interface with wide\-band oxygen sensors to automaticly adjust a wide range throttle positions and RPM ranges to deliver unmatched performance and driveability like no other product in the industry\. ThunderMax® is made in the USA and comes 100% assembled, ready to install with no wire\-cutting or splicing required\. Simply replace the factory ECM and oxygen sensors, load a map, and enjoy your new ride\! \

Not legal for sale or use in California on any pollution controlled motor vehicle\. Not legal for sale or use on any EPA pollution controlled motor vehicle\.\ - [\#517\-872 ZIPPERS M8 128" CYLINDER / DOMED PISTON KIT, 117" to 128" kit with Thermal Coated \+1\.9cc domed pistons designed to be used with modified heads](https://www.zippersperformance.com/517-872-zippers-m8-128-cylinder-domed-piston-kit-117-to-128-kit-with-thermal-coated-1-9cc-domed-pistons-designed-to-be-used-with-modified-heads/) - [\#517\-863 ZIPPERS M8 128" CYLINDER/\+1\.9CC PISTON KIT, 114\-117" to 128" kit with Thermal Coated \+1\.9cc domed pistons designed to be used with modified heads](https://www.zippersperformance.com/517-863-zippers-m8-128-cylinder-1-9cc-piston-kit-114-117-to-128-kit-with-1-99cc-domed-pistons-designed-to-be-used-with-modified-heads/) - [Zipper's Milwaukee\-Eight® Big Bore Cylinder Kits](https://www.zippersperformance.com/zippers-m8-cylinder-kit/): Increasing the size of a Milwaukee\-Eight® engine is easy with Zipper’s Big Bore Cylinder Kits\. The Milwaukee\-Eight® engine design is ideal for displacement increases and Zippers offers these 4\.250" cylinder kits for the factory stock 4\-valve head, SE heads, of course our own Zipper's CNC ported and many other custom high flow heads to provide huge torque and horsepower gains\. Each of these specific bore sizes are designed to fit on the factory engine base without case boring for just\-like\-stock installation\. These castings are designed with additional aluminum for added strength vs the O\.E\. casting, with a larger bore liner and the following features: • Cast Aluminum has 1 lb\. Additional Material for Strength and Reliability • Stress Relieved Iron Liners • Precision Sized on Sunnen SV\-30 by Zipper’s skilled craftsman • 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 many dome configurations to choose from so you can target various compression ratios\. Contact Zipper's support if you have a special requirement\. Increasing the bore  to 4\.250 on a 107 \(4\.375 stroke\) M8 = 124ci Increasing the bore  to 4\.250  on a 114/117 \(4\.500 stroke\) M8 = 128ci Kits include precision fitted cylinders with tight tolerances, 2618 forged pistons with advanced ring packs, pins \& clips, head and base gaskets and new head bolts\. The rings provided are custom sized to each cylinder\.  These kits are provided with Cometic \.014" base and \.030" head gaskets, which usually allow for \.035"\-\.042" piston\-to\-head "squish"\.  The additional gaskets listed allow the builder to fine tune "squish" for optimum power should your build fall outside of the standard \.035"\-\.042" spec\. \

Not legal for sale or use in California on any pollution controlled motor vehicle\. Not legal for sale or use on any EPA pollution controlled motor vehicle\.\   \

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\ ## Product categories - [All Products](https://www.zippersperformance.com/all-products/engine-transmission/miscellaneous-parts-and-accessories/all-products/) - [Engine/Transmission](https://www.zippersperformance.com/all-products/engine-transmission/) - [Performance Power Train](https://www.zippersperformance.com/all-products/performance-power-train/) - [Uncategorized](https://www.zippersperformance.com/all-products/uncategorized/) - [Tools](https://www.zippersperformance.com/all-products/tools/) ## Product MPN - [90226](https://www.zippersperformance.com/mpn/90226/) - [90231](https://www.zippersperformance.com/mpn/90231/) - [12604](https://www.zippersperformance.com/mpn/12604/) - [42504](https://www.zippersperformance.com/mpn/42504/) - [12504](https://www.zippersperformance.com/mpn/12504/) ## Optional - [Sitemap index](https://www.zippersperformance.com/sitemap_index.xml)