| Component | Specification |
|---|---|
| Engine | Screamin’ Eagle Twin Cam 110B (1801cc) |
| Years Produced | 2016 – 2017 |
| Oil Type & Capacity | SAE 20W50 (3.3 L) |
| Tire Size (Front) | MT90B16 72H |
| Tire Size (Rear) | MU85B16 77H |
| Spark Plug | Harley-Davidson 6R12 |
| Battery | 65989-97E |
The Harley-Davidson Softail Slim S (FLSS) represents a pivotal moment in the Motor Company’s history: it was the first time the high-performance Screamin’ Eagle 110B engine—previously a luxury reserved exclusively for the high-priced Custom Vehicle Operations (CVO) lineup—was shoehorned into a standard production Softail chassis. This ‘hot-rod’ engineering approach created a sleeper bobber with a power-to-weight ratio that remains legendary among Milwaukee-Eight predecessors.
Engineering Analysis: The 110B Powerplant
At the heart of the FLSS is the air-cooled Twin Cam 110B, featuring counter-balancers to mitigate the vibration inherent in the rigid-mounted Softail frame. This engine produces approximately 107 lb-ft of torque at 3,500 RPM. From a technical perspective, the ‘S’ variant is distinguished by its blacked-out aesthetic and the heavy-breather intake, which requires specific attention during routine maintenance to ensure optimal air-to-fuel ratios.
Maintenance Roadmap
To maintain the high-performance standards of the FLSS, adherence to the following technical specifications is mandatory:
1. Lubrication System
The FLSS utilizes a dry-sump lubrication system. It requires 3.3 Liters of SAE 20W50 oil. For high-temperature climates or heavy touring, synthetic fluids are recommended to protect the larger 110-cubic-inch cylinders from thermal breakdown.
2. Wheel and Tire Integrity
Proper contact patches are critical for managing the 110B’s torque. The front uses an MT90B16 72H while the rear utilizes an MU85B16 77H. Optimal handling is achieved at 2.5 bar (36 psi) in the front and 2.9 bar (42 psi) in the rear.
3. Electrical and Ignition
The ignition system relies on Harley-Davidson 6R12 spark plugs. Given the high compression of the Screamin’ Eagle engine, ensuring the gap is within factory spec is vital for preventing pre-detonation. The electrical system is powered by the 65989-97E battery, which should be kept on a tender during storage to maintain the high cold-cranking amps required to turn over the 1,801cc V-Twin.
MotoSpecsLab Expert Verdict
The FLSS is a modern classic that bridges the gap between old-school bobber aesthetics and CVO-level performance. It requires diligent maintenance of its cooling surfaces and precise tire pressure management to handle its significant torque output. For the owner-mechanic, it remains one of the most rewarding Twin Cam models to service due to its straightforward mechanical layout and high-quality components.