Forged Piston Kit — Milwaukee-Eight 124

CP-Carrillo forged piston kit for Milwaukee-Eight 124 Harley-Davidson engines — the same pistons serious engine builders spec for high-output baggers. Forged in the USA from high-strength 2618 aluminum alloy for strength under boost, nitrous and high compression.

Race / competition use: this is an engine performance component. It is not legal for use or installation on pollution-controlled vehicles operated on public highways in California, and it cannot be shipped to California.

FITMENT

• Engine: Milwaukee-Eight
• Application years (CP-Carrillo data): 2017–2022
• Big-bore / performance application — requires matching cylinders and machine work (see Installation).

Not sure it fits your bike? Email info@norcalbaggersupply.com — email is the fastest way to reach us — and we'll confirm before you order. You can also call 916-626-9030 (Mon–Fri, 9 AM–5 PM PT).

SPECIFICATIONS

• BHM8124-3.9 — Bore 4.18 in, stroke 4.5 in, 11.0:1 compression, dome -3.9 cc, compression height 1.08 in, wrist pin 927-2250-18CP1C, ring set 1-MG10-4180 2-MS20-4180-THG 3-M38-4180
• M5100A — Bore 4.25 in, stroke 4.375 in, 11.0:1 compression, dome -4 cc, compression height 1.143 in, wrist pin 927-2250-18CP1C, ring set 1-MS18-4250 2-MS28-4250-THG 3-D30-4250-0
• M5101A — Bore 4.25 in, stroke 4.375 in, 11.5:1 compression, dome 1 cc, compression height 1.143 in, wrist pin 927-2250-18CP1C, ring set 1-MS18-4250 2-MS28-4250-THG 3-D30-4250-0
• M5102A — Bore 4.25 in, stroke 4.375 in, 12.0:1 compression, dome 5.3 cc, compression height 1.143 in, wrist pin 927-2250-18CP1C, ring set 1-MS18-4250 2-MS28-4250-THG 3-D30-4250-0

Kit includes two pistons, ring sets, wrist pins and clips. Made in the USA by CP-Carrillo.

INSTALLATION

Professional installation by a qualified engine builder or machine shop is required. Cylinders must be bored and honed to the finished piston size, and ring end gaps, piston-to-wall clearance and deck height set to CP-Carrillo's specifications for your build. Pistons only — cylinders and gaskets are not included.

QUESTIONS RIDERS ASK

Is this a complete kit?
Yes — each set covers both cylinders: two pistons, ring sets, wrist pins and clips.

Does it fit my 2023.5+ Milwaukee-Eight?
CP-Carrillo's application data for these part numbers covers 2017–2022 Milwaukee-Eight engines. If your bike is a 2023.5 or newer Gen 2 model, email us first and we'll confirm the right part number with CP-Carrillo before you order.

Can I order a single replacement piston?
Singles exist in CP-Carrillo's line for service work. Email us the part number off your piston and we'll price a single through our dealer account.