Harley-Davidson STREET GLIDE ST (117 CUI) – FLHXST Service Guide: Oil Level & Tire Specs

The Harley-Davidson Street Glide ST (FLHXST) represents a pivotal shift in the Grand American Touring lineup. Historically, the 117 cubic-inch Milwaukee-Eight engine was a luxury reserved exclusively for the Custom Vehicle Operations (CVO) models. With the introduction of the ST, Harley-Davidson brought this high-displacement powerhouse to a production performance bagger, directly inspired by the competitive ‘King of the Baggers’ racing circuit.

Engineering Overview: The 117 Milwaukee-Eight

At the heart of the FLHXST is the 1923cc V-Twin, utilizing a precision oil/air cooling system. This engine is optimized for high-end torque, producing 125 ft-lb at 3500 RPM. Unlike the standard Street Glide, the ST features a Heavy Breather intake and a high-performance camshaft to maximize volumetric efficiency. From a technical standpoint, the dual-plug cylinder heads require four 6R10 spark plugs to ensure complete combustion across the large bore.

Maintenance Protocol & Fluids

To maintain the integrity of the 117 CUI engine, MotoSpecsLab recommends a strict adherence to fluid quality. The primary lubricant choice is Screamin’ Eagle Syn3 Full Synthetic 20W50, particularly for riders in warmer climates or those engaging in spirited touring. The system requires 3.8 liters for a full filter-change service.

Tires and Chassis

The FLHXST utilizes a specific tire combination to balance heavy-duty touring stability with cornering agility. The front 19-inch wheel is wrapped in a 130/60B19, while the rear 18-inch wheel carries a 180/55B18. Maintaining the correct pressure—36 psi front and 42 psi rear—is critical for preventing cupping and ensuring the longevity of the Dunlop Harley-Davidson Series rubber.

MotoSpecsLab Editorial Review

The Street Glide ST is the ‘purist’s bagger.’ By stripping away the rear seat and passenger pegs and focusing on the 117 CUI powertrain, Harley-Davidson created a machine that feels significantly more athletic than its predecessors. The inclusion of the Reflex Defensive Rider Systems (RDRS) as a standard or highly recommended option provides the electronic oversight necessary to manage the massive torque output in adverse conditions.