| Component | Specification |
|---|---|
| Engine | Milwaukee-Eight 107 (1745cc) |
| Oil Type | SAE 20W50 |
| Oil Capacity | 3.8 Liters |
| Front Tire | 130/60B19 61H (36 psi / 2.48 bar) |
| Rear Tire | 180/55B18 80H (42 psi / 2.90 bar) |
| Battery | 66010-97D |
| Spark Plugs | 6R10 (Quantity: 4) |
Engineering Highlight: The Custom Revolution
The 2017-2018 Road King Special (FLHRXS) represents a pivotal moment in Harley-Davidson’s design philosophy. It was the first model to replace the traditional chrome-heavy ‘King’ aesthetic with a fully blacked-out, ‘dark custom’ finish from the factory. More significantly, it debuted the Milwaukee-Eight 107 engine in a stripped-down bagger chassis, utilizing dual spark plugs per cylinder (4 total) to achieve Euro 4 compliance while increasing torque by 10% over its predecessor.
Technical Deep Dive: The Milwaukee-Eight 107 Heart
The FLHRXS/107 is powered by the 1745cc Milwaukee-Eight, a four-valve-per-cylinder V-Twin that marked a return to a single camshaft design. This configuration reduces mechanical noise and allows for a slimmer primary cover, improving rider ergonomics. The Euro 4 models are specifically tuned to balance lean-burn efficiency with the signature Harley-Davidson exhaust note, managed through advanced O2 sensor feedback loops.
Maintenance Guide & Essentials
Lubrication System
For optimal thermal management in the Milwaukee-Eight engine, MotoSpecsLab recommends SAE 20W50 synthetic motorcycle oil. The system requires 3.8 Liters for a full change including the filter. Regular inspection of the primary chaincase and transmission fluids is also essential for the 6-speed Cruise Drive transmission.
Chassis and Contact Patch
The Road King Special features unique turbine-style cast aluminum wheels. Maintaining the correct pressure is critical for handling stability on this 372kg (wet) machine. Ensure the 19-inch front is at 36 psi and the 18-inch rear is at 42 psi. The lower profile tires on the Special model provide sharper turn-in response compared to the standard Road King.
Electrical & Ignition
The ignition system utilizes four Harley-Davidson 6R10 spark plugs. The dual-plug setup ensures more complete combustion and smoother idling. For starting reliability, the 66010-97D battery provides the high cold-cranking amps required to turn over the high-compression 107 cubic inch cylinders.
Editor’s Verdict
The FLHRXS/107 is the purist’s choice for a modern bagger. By removing the windshield and chrome, Harley-Davidson highlighted the mechanical beauty of the Milwaukee-Eight engine. From a technical perspective, the Euro 4 107 remains one of the most reliable iterations of the new powertrain, offering a perfect balance of performance and long-term serviceability.
Frequently Asked Questions
What spark plugs does the FLHRXS 107 use?
The model uses four Harley-Davidson 6R10 spark plugs to support its dual-ignition system.
How much oil is needed for an oil change?
A standard oil change with filter replacement requires 3.8 liters of SAE 20W50 oil.
What is the correct tire pressure for the Road King Special?
Front: 36 psi (2.48 bar). Rear: 42 psi (2.90 bar).