This engine will provide a significant power increase – 11 percent more horsepower and 6 percent more torque – over the 2024 Fat Boy 114 model.
Review – Key Features – Features & Benefits – Specifications
2025 Harley-Davidson Milwaukee-Eight 117 Custom Engine: SIGNIFICANT POWER BOOST.
Introducing the 2025 Harley-Davidson Milwaukee-Eight 117 Custom Engine…
Milwaukee-Eight 117 Custom (powers Fat Boy and Breakout models) is tuned to deliver 104 horsepower (78 kW) and 126 lb. ft. (171 Nm) peak torque, 6 percent more power and 5 percent more torque (U.S. spec) than the Milwaukee-Eight 117 Classic engine for a performance boost. This engine will provide a significant power increase – 11 percent more horsepower and 6 percent more torque – over the 2024 Fat Boy 114 model. This engine is equipped with a 2-into-2 exhaust with individual catalysts. The Touring-style intake airbox volume is 4.0 liters, approximately 50 percent greater than 2024 Ventilator (Fat Boy model) and Heavy Breather (Breakout model) intakes, which improves power by providing more room for the in-molded velocity stack radius and greater volume of clean air. Intake noise is significantly reduced, which allows a more desirable, rumbling exhaust tone to predominate.
2025 Harley-Davidson Milwaukee-Eight 117 Custom Engine Totalmotorcycle.com Key Features
Three New Milwaukee-Eight 117 Powertrains – The 2025 Cruiser models will be powered by one of three new Milwaukee-Eight 117 powertrain variants with new cylinder heads, throttle body and intake manifold. Each is tuned – through difference in intake and exhaust scheme and ride mode programming – to offer performance that matches the personality of a specific Cruiser model and the anticipated expectations of that model’s customer. Each engine is Euro V+ Compliant (2024 emissions standards). Shared features of these engines include:
- NEW Four-Valve Cylinder Heads feature the combustion chamber shape, oval intake ports and low-profile intake valve seats as introduced on 2023/24 Milwaukee-Eight 117/121 engines for Grand American Touring and CVO models. These heads are designed to improve performance and fuel economy.
- NEW Engine Oil is routed from a frame-mounted oil cooler through cylinder head cooling passages. This cylinder head cooling system further optimizes thermal comfort for the rider, especially in low-speed riding situations and hot weather. This air/oil cooled version of the Milwaukee-Eight 117 engine weighs less that the Grand American Touring/CVO versions of the engine and does not require coolant system maintenance.
- NEW Contoured Aluminum Intake Manifold offers a more-direct air path and creates a smooth transition from the round throttle body to the new oval intake ports to enhance intake air flow for improved power and reduced exhaust emissions.
- NEW Improved Sound Quality as muffler and intake have been designed to enhance sound quality and match the character of each engine variant. Mufflers feature advanced lightweight material that works to trim high frequencies and emphasize low frequencies for a powerful sound.
- Dual Counter-Balancers are tuned to eliminate primary vibration at idle while permitting some engine character to shine through at speed.
- V-Twin Design with 45-degree cylinder angle maintains classic Harley-Davidson look-sound-feel.
- Compression Ratio of 10.3:1 enhances torque at lower RPM and improves fuel economy.
2025 Harley-Davidson Milwaukee-Eight 117 Custom Engine Totalmotorcycle.com Features and Benefits
- NEW Milwaukee-Eight 117
- A Milwaukee-Eight 117 powertrain with more displacement and enhanced intake and exhaust flow offers 105 horsepower (78 kW) and 130 lb. ft (176 Nm) of peak torque, 6.6 percent more torque and 12.9 percent more horsepower than the Twin Cooled Milwaukee-Eight 114 powertrain in 2024 Grand American Touring models.
- Milwaukee-Eight 117-cylinder head cooling system further optimizes engine temperatures, especially in low-speed riding situations and hot weather, compared to 2024 Twin-Cooled Milwaukee-Eight 114 engine.
2025 Harley-Davidson Milwaukee-Eight 117 Custom Engine – Totalmotorcycle.com Specifications/Technical Details
| Engine | Milwaukee-Eight® 117 Custom | |
| Valves | Pushrod-operated, overhead valves with hydraulic, self-adjusting lifters; four valves per cylinder | |
| Bore | 4.075 in. (103.5 mm) | |
| Stroke | 4.5 in. (114.3 mm) | |
| Displacement | 117 cu in (1,923 cc) | |
| Compression Ratio | 10.3:1 | |
| Fuel System | Electronic Sequential Port Fuel Injection (ESPFI) | |
| Air Cleaner | Helix style A/C | |
| Exhaust | 2-into-2 staggered; catalyst in muffler | |
| Lubrication System | Pressurized, dry-sump with oil cooler |
Manufacturer Specifications and appearance are subject to change without prior notice on Total Motorcycle (TMW).
