Harley-Davidson Milwaukee-Eight 128” Big Bore Kit Unleash the full performance potential of your Harley-Davidson Milwaukee-Eight engine with our premium 128” Big Bore Kit. Designed for riders who demand real horsepower and torque gains, this kit transforms your stock M8 into a hard-pulling performance motor with stronger acceleration, improved throttle response, and increased top-end power. This kit is engineered to convert: M8 107” → 124” M8 114” / 117” → 128” Built with proven performance components, the kit includes CP forged pistons for strength and durability under high load conditions, along with Cometic gaskets to ensure reliable sealing and long-term engine integrity. Whether you're building a performance bagger, hot street cruiser, or dyno-tuned torque monster, this big bore upgrade delivers the displacement and power increase serious riders are looking for.