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S&S Cycle 129" Big Bore Kit For Harley 107" Milwaukee Eight 2017-2023

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This item is available as a Blem/Refurb. These are items that cannot be sold as "New" merchandise and are limited to stock on hand. See the product details for a description of the product's condition.

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This product is legal in California only for racing vehicles which may never be used, registered or licensed for use upon a highway.

S&S Cycle 129" Big Bore Kit For Harley 107" Milwaukee Eight 2017-2023 Resources

S&S Cycle 129" Big Bore Kit For Harley 107" Milwaukee Eight

Turn your 107 cubic inch Milwaukee Eight into a 129 cubic inch monster. S&S Cycle has done it again with their bolt-on big bore kit featuring a 4.32” bore and 11:1 compression ratio. This cylinder and piston kit will accommodate a high lift cam and keep your Harley-Davidson M8 happy on pump gas. No case mods, no engine removal; just a massive set of jugs, designed, tested, and manufactured here in the USA.


  • Huge bore increase means huge power increase 
  • Works with stock crankcases (no machine work) 
  • Powder coat finish matches factory finish 
  • MLS (multi-layered steel) head gaskets 
  • 4.320" Bore 
  • Retains stock engine height 
  • Includes cubic inch cam cover badge 
  • Made in USA  
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Please review this product's fitment notes & exceptions prior to purchase: Add to Cart

This product is vehicle specific. Click here to select your vehicle to ensure fitment.

Fitment Notes & Exceptions
  • Fits models with 107" Milwaukee Eight engines only

This Product Fits:

Harley Davidson
Electra Glide Standard FLHT 2019, 2020, 2021, 2022
Electra Glide Ultra Classic FLHTCU/I 2017, 2018, 2019
Electra Glide Ultra Limited FLHTK 2017-2023
Electra Glide Ultra Limited Low FLHTKL 2017, 2018, 2019
Revival FLH 2021
Road Glide FLTRX 2017-2023
Road Glide Limited FLTRK 2020, 2021, 2022, 2023
Road Glide Special FLTRXS 2021, 2022, 2023
Road Glide ST FLTRXST 2022, 2023
Road Glide Ultra FLTRU 2017, 2018, 2019
Road King FLHR/I 2017-2022
Softail Breakout FXBR 2018, 2019
Softail Deluxe FLDE 2018, 2019, 2020
Softail Fat Bob FXFB 2018, 2019
Softail Fat Boy FLFB 2018, 2019
Softail Heritage Classic FLHC 2018, 2019, 2020, 2021
Softail Low Rider FXLR 2018, 2019, 2020
Softail Low Rider S FXLRS 2020, 2021, 2022, 2023
Softail Low Rider ST FXLRST 2022, 2023
Softail Slim FLSL 2018, 2019, 2020, 2021
Softail Sport Glide FLSB 2018, 2019, 2020, 2021
Softail Standard FXST 2020, 2021, 2022, 2023
Softail Street Bob FXBB 2018, 2019, 2020
Street Glide FLHX/I 2017-2023
Street Glide Special FLHXS 2021, 2022, 2023
Street Glide ST FLHXST 2022, 2023
Product Style Item # Store SKU Manufacturer Product # Availability
Product Style Non-Highlighted Fins Item # 10281738 Store SKU Manufacturer Product # 910-0844 Availability In Stock: Ships in 1-2 business days
Product Style Highlighted Fins Item # 10281737 Store SKU Manufacturer Product # 910-0843 Availability In Stock: Ships in 1-2 business days
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