2025 Harley-Davidson® Street Bob® The new Milwaukee-Eight® 117 Classic engine is tuned for street performance with a wide, flat torque curve, meaning you have a handful of power whenever you grab for it.New two-into-one exhaust enhances engine performance by using a lightweight acoustic material that maximizes flow while providing a deep, muscular sound.The rear monoshock with under-seat, cam-style pre-load adjustment helps you keep the ride smooth, no matter the load or what the road throws at you.