| Specification | Value |
|---|---|
| Model Series | FLHX / Street Glide (107 CUI) |
| Production Years | 2017-2021 |
| Engine Type | Milwaukee-Eight 107 V-Twin |
| Engine Oil | SAE 20W-50 (3.8 L) |
| Front Tire | 130/60B19 61H (36 psi / 2.48 bar) |
| Rear Tire | 180/65B16 81H (40 psi / 2.76 bar) |
| Battery Model | 66000175 |
| Spark Plug | H-D 6R10 |
Engineering Highlight: The 2017 introduction of the Milwaukee-Eight 107 engine marked only the ninth Big Twin engine design in Harley-Davidson’s 114-year history. This powerplant revolutionized the touring lineup by introducing a four-valve cylinder head design and dual spark plugs per cylinder, resulting in a 10% increase in torque and significantly improved heat management compared to its Twin Cam predecessor.
Technical Deep-Dive: The Milwaukee-Eight 107
The FLHX Street Glide (107 CUI) represents the pinnacle of Harley-Davidson’s touring evolution. The engine features a single internal counter-balancer that cancels 75% of primary vibration at idle, maintaining the classic “Harley feel” while providing a smoother experience at highway speeds. The 107 cubic inch (1746cc) displacement delivers power through a refined 6-speed Cruise Drive transmission, specifically geared for low-RPM cruising and high-torque overtaking.
Maintenance Guide & Fluid Logistics
To maintain peak performance and longevity of the Milwaukee-Eight platform, MotoSpecsLab recommends the following intervals:
- Engine Oil: Utilize 3.8 Liters of SAE 20W-50. For extreme temperature operation, synthetic Screamin’ Eagle Syn3 is preferred to resist thermal breakdown.
- Ignition System: The H-D 6R10 spark plugs should be inspected every 5,000 miles. The dual-plug setup ensures more efficient combustion but requires precise gapping.
- Electrical: The 66000175 battery is a high-CCA (Cold Cranking Amp) unit essential for turning over the high-compression 107 engine. Always use a dedicated AGM tender during storage.
Chassis and Handling Analysis
The FLHX/18 chassis benefited significantly from the 2017 suspension overhaul. The front end utilizes Showa Dual Bending Valve (SDBV) technology, providing the damping performance of a racing-style cartridge fork with lighter weight. The rear suspension features emulsion-technology shocks with a single hand-adjustable pre-load knob, eliminating the need for air pumps and ensuring consistent contact patches for the 180/65B16 rear tire.
Frequently Asked Questions (FAQ)
What is the recommended tire pressure for a loaded Street Glide?
For the FLHX/18, the front should remain at 36 psi (2.48 bar), while the rear should be strictly maintained at 40 psi (2.76 bar) to handle the weight of the Batwing fairing and loaded saddlebags.
Can I use 10W-40 oil in the 107 Milwaukee-Eight?
No. Harley-Davidson specifies SAE 20W-50. Using lower viscosity oils may lead to inadequate lubrication at operating temperatures and increased mechanical noise from the valve train.
How often should the air filter be serviced?
The high-flow air cleaner on the 107 CUI should be inspected every 5,000 miles and replaced or cleaned more frequently in dusty environments to maintain the correct stoichiometric ratio.