Zipper’s 128″ Big Bore Kit for 2017-Newer M-Eight Harley 114/117 Touring Models




The Zipper’s 128″ Big Bore Kit is a reliable way to increase power and torque on your 2017-Newer M-Eight Harley Touring Engine. This is a complete kit that includes heads, cylinders, pistons, gaskets and ring set. Cycle Solutions keeps as many kits in stock as possible. Some kits can be shipped immediately and some may need to be manufactured.. As a result, we keep you on the road and not sitting in the shop. A core exchange is required on this kit.  Reach out to us if you would like to know if a kit is in stock or once ordered we will reach out to you.




Zipper’s Muscle 128” Big Bore Kit for the 114”-117” M8 is the most powerful top end kit produced.  The big breathing 4-valve heads on the M-Eight just love displacement, so this kit was developed for use with a 4.25” Bore drop-on cylinder.  These cylinders are fitted with flat-top forged pistons and topped off with Zipper’s Stage III CNC headwork.

This kit includes CNC ported heads, bored cylinders, pistons, required gaskets and ring set.   A core exchange is required.  Click here for core exchange information.  This kit can be modified for additional performance parts by reaching out to us.

Cycle Solutions Inc offers installation and dyno tuning at our two shop locations and at the events we attend for an additional cost of $1400.00. If you are interested in having this kit professionally installed and dyno tuned or have questions about this kit then please click below.

Fitment: 2017-Newer M-Eight Harley 114/17 Touring Models


  • Advanced port and valve designs works great with flat-top pistons
  • Oversize 41mm Intake, 33mm Exhaust Valves
  • Supports140+HP/TQ On 4.125-4.250″ Bore Engines
  • Performance Valve Springs Set Up for Cam
  • Decking to Achieve 92.5cc Combustion Chamber

Cylinders & Pistons:

  • 4.25” (124”) Big Bore Cylinder Kit
  • Forged 10:9:1 compression ratio flat-top pistons
  • Gasket Kit

To get the most performance out of this Zipper’s 128″ Big Bore Kit it must be paired with the proper supporting products. We recommend a high cranking amp battery, a stepped exhaust system, Hi flow air intake, Thundermax Auto tune, a red shift 552 chain drive cam, 58mm-62mm CSR throttle body , 7.1 GPS Injectors and the S&S Roller Rocker Guardian Upgrade Kit.

PLEASE NOTE: If you order the S&S Roller Rocker Guardian Kit then you do not need to order the Feuling ARP kits because the Guardian kit includes the S&S Bolt Kit.


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