As if a 1.8-liter V-Twin was not enough, Harley-Davidson offers owners a way to bore up their engine to as much as 2.2-liters using just bolt-on parts. These are made possible by Screamin’ Eagle (Harley-Davidson’s performance line of parts) Stage IV kits.
The kits were specially-designed for Milwaukee-Eight engines fitted to Touring models sold with model year 2017 onwards. These kits fit 107CI (1.8-liter) and 114 / 117 CI (1.89/1.92-liter) engines and turn them into 128CI (2.1-liter) and 131CI (2.15-liter) engines respectively; providing up to a 260cc increase in displacement. Best of all, these kits are covered under Harley-Davidson’s Custom Coverage warranty when dealer-installed up to 2 years within 60 days of the motorcycle’s purchase.
128Ci Stage IV kit
The 107CI Stage IV kits includes CNC-ported heads with 1mm bigger valves and fully-machined combustion chambers. It also comes with a high-lift cam, high-compression pistons, and a 64mm throttle body and intake manifold. These parts combine to deliver 121 HP and 126 ft-lb of torque straight to the rear-wheel when paired with Screamin' Eagle Street Cannon Mufflers.
131CI Stage IV kit
The 114/117CI kit comes with CNC-ported heads with 1mm bigger valves and fully machined combustion chambers. It comes with a high-lift cam, high-compression pistons and a 64mm throttle body and intake manifold. This delivers a similar 121 HP and a whopping 131 ft-lb of torque direct to the rear-wheels when paired with Screamin' Eagle Street Cannon Mufflers.
Be warned that these kits were specifically designed to Harley-Davidson’s touring models and may not be compatible with other lines. Some models may require other parts like a high-capacity oil pump or high-capacity Clutch plate kit. All models require additional purchase of ECM recalibration with the Screamin' Eagle Pro Street Tuner for proper installation.
Nonetheless, your nearest Harley-Davidson dealer will be able to tell you about its compatibility with your motorcycle.