| Specification | Value |
|---|---|
| Engine | Milwaukee-Eight® 121 VVT |
| Production Years | 2023–Present |
| Oil Capacity | 4.7 L (SAE 20W-50 Syn3) |
| Front Tire | 130/60B19 M/C 61H (36 psi) |
| Rear Tire | 180/55B18 M/C 80H (42 psi) |
| Spark Plugs | 6R10A (31600106) |
| Battery | 66000302 (Lithium LiFePO4) |
The 2024 Harley-Davidson CVO Street Glide (FLHXSE) represents a pivotal moment in American motorcycle engineering. It is the first Grand American Touring model to implement Variable Valve Timing (VVT), a technology that broadens the overall powerband and improves thermal efficiency. This engineering leap allows the 121-cubic-inch Milwaukee-Eight engine to deliver high-end horsepower without sacrificing the low-end torque characteristic of the H-D brand.
Engineering Overview: The 121 VVT Powerplant
Unlike previous CVO iterations that relied solely on increased displacement, the FLHXSE/24 utilizes a 1,977cc V-Twin with liquid-cooled cylinder heads. The integration of VVT advances or retards the camshaft timing over a range of 40 degrees of crankshaft rotation. For the technician, this means the timing chest is significantly more complex than the standard M8, requiring specialized tools for cam service.
Maintenance Guide & Technical Requirements
1. Lubrication System
The 121 VVT engine is highly sensitive to oil shear and thermal breakdown. MotoSpecsLab recommends using only SAE 20W-50 Syn3 Full Synthetic. The total system capacity is 4.7 Liters. Given the increased heat profile of the high-compression 121 heads, maintaining the oil level at the ‘Full’ mark on the dipstick (checked hot) is critical for the hydraulic lifters and VVT actuator performance.
2. Electrical & Starting System
The FLHXSE/24 has transitioned to a high-output Lithium LiFePO4 battery (Part #66000302). This reduces weight significantly but requires a lithium-specific constant-current/constant-voltage (CCCV) charger. Standard lead-acid tenders can damage the internal Battery Management System (BMS).
3. Chassis and Contact Patch
Handling precision is maintained through specific Dunlop Harley-Davidson Series tires. To prevent cupping and ensure the stability of the inverted 47mm front forks, pressures must be strictly maintained at 36 psi front and 42 psi rear. The rear suspension features remote preload adjustment, which should be calibrated based on the combined rider and luggage weight to maintain the correct rake and trail geometry.
Technical FAQ
What spark plugs are required for the CVO 121?
The engine utilizes 6R10A (31600106) plugs. Due to the high compression and VVT timing maps, using non-standard heat range plugs can lead to pre-detonation (knock) detected by the Ion Sensing system.
How often should the VVT system be inspected?
While the VVT actuator is designed for the life of the engine, the oil supply to the solenoid is filtered. Ensuring clean oil at the 5,000-mile interval is the primary preventive measure for VVT longevity.
Editor’s Note: The FLHXSE/24 is a high-performance machine. All torque values should be verified against the 2024 CVO Service Manual Supplement before performing chassis or engine work.