Availability: Approx. Week of May 4th, 2026.
Fuel Moto 128" Big Bore Kit for Gen 2 117" M8 Engines
The Fuel Moto M8 128"piston & cylinder kits takes your 2024-2025 Harley Davidson Gen 2 Milwaukee-8 117" engine to 128" without engine case boring. Includes choice of CP Carrillo pistons with 11.0:1 or 11.5:1 compression ratio. Includes new 4.250" cylinders, and Cometic MLS heads & base gaskets. This kit works on 2024-later Milwaukee-Eight 117" 4.5" stroke engines (Gen 2) Touring & Softail. Recommended for use with Gen 2 specific camshafts.
proprietary FM custom CP Carrillo pistons choice of 11.0:1, or 11.5:1 compression ratio, premium X-forging with fully developed skirt profile. The ring end gap is already set and are simply ready to be installed.
The Fuel Moto M8 128" big bore kit includes new Extreme Duty cylinders with high strength ductile iron sleeves, bore/hone finish work is done on OEM level machinery to exact tolerances. Cylinders have black finish with silver polished highlights. Manufactured by S&S Cycle in Viola, WI USA. MLS head & base gaskets are included.
You will need an exhaust system, air cleaner, EFI tuner, and clutch spring and/or lockup to support the appropriate power level of this kit. Milwaukee-8 engines also require larger fuel injectors. Fuel Moto engine kits require installation by a qualified mechanic with experience in engine building and the appropriate tools to check all clearances & tolerances during engine assembly following the OEM service manual procedures and any additional instructions provided. You will need a OEM service manual and some specialty tools such as a inner cam bearing removal/install tool. These engine kits also require comprehensive EFI tuning by a tuner with experience & knowledge of Gen 2 tuning strategies. Power Vision and Thundermax base maps are available for assorted application, please contact us for details & availability. Check our FM University site for helpful tips and info.
You have done all of your research but maybe you still have a question. The technicians at Fuel Moto have the answers and would welcome your call. With every Fuel Moto big bore kit purchase we include unlimited technical support. Shoot us an email at info@fuelmotousa.com or give us a call at 920-423-3309 - we will work together to get you up and running.
Available at our location including the complete kit, break in & dyno tune on our state of the art dyno. (*does not include EFI tuning device, exhaust system, throttle body, injectors or other associated parts such as oil & filter)
