| Component | Specification |
|---|---|
| Engine | Milwaukee-Eight 107 V-Twin (1,745cc) |
| Model Years | 2017-2018 |
| Engine Oil | Harley-Davidson 360 20W50 (4.3 Liters) |
| Spark Plugs | HD-6R10 |
| Battery | Part No. 66000174 |
| Front Tire | MT130/60B19 70H (2.48 bar / 36 psi) |
| Rear Tires | P205/65R15 92T (1.79 bar / 26 psi) |
The 2017 release of the FLHTCUTG marked a watershed moment in Harley-Davidson’s three-wheel history. This was the inaugural year the Milwaukee-Eight 107 engine was integrated into the Tri Glide chassis. Unlike the previous Twin Cam powerplants, the 107 introduced a four-valve-per-cylinder head design and a counter-balancer that reduced 75% of primary vibration while idling, significantly improving the thermal comfort for both rider and passenger.
Engineering Analysis: The Milwaukee-Eight 107
The FLHTCUTG/17 utilizes the precision-cooled version of the Milwaukee-Eight 107. This system employs targeted oil cooling around the exhaust valves to maintain consistent performance under heavy load—critical for a vehicle with a curb weight exceeding 1,200 lbs. The increased displacement and higher compression ratio (10.0:1) deliver approximately 10% more torque than its predecessor, providing the necessary grunt for highway overtaking without frequent downshifting.
Maintenance Protocols
As the Editor-in-Chief of MotoSpecsLab, I emphasize that the Tri Glide Ultra requires specific attention to its unique chassis dynamics. The rear differential and independent suspension components must be inspected alongside standard engine intervals.
Lubrication System
The 107 CUI engine requires 4.3 Liters of Harley-Davidson 360 20W50. Due to the high-heat nature of the rear-cylinder positioning in a trike configuration, synthetic upgrades (such as Screamin’ Eagle SYN3) are highly recommended for riders in warmer climates to prevent viscosity breakdown.
Ignition and Electrical
The 2017-2018 models utilize the HD-6R10 spark plugs. Proper gapping is essential to ensure the dual-plug heads fire in perfect synchronization. For electrical reliability, especially given the high draw of the Boom!™ Box Infotainment system, the 66000174 battery must be kept on a tender during off-season storage to maintain its cold cranking amp (CCA) integrity.
Tire and Chassis Management
Handling on a trike is entirely dependent on tire footprint. The front 19-inch wheel (MT130/60B19) acts as the primary steering pivot and must be maintained at 2.48 bar (36 psi). The rear automotive-style tires (P205/65R15) require a lower pressure of 1.79 bar (26 psi) to allow the sidewalls to absorb lateral forces during cornering, preventing the ‘tippy’ sensation common in over-inflated trike setups.
Summary
The FLHTCUTG/17 remains one of the most stable and powerful long-distance touring platforms in the H-D lineup. By adhering to the specified 107 CUI maintenance schedule and paying close attention to trike-specific tire pressures, owners can ensure the longevity of this sophisticated Milwaukee-Eight machine.