Harley-Davidson has officially released a new motor, the Milwaukee Eight™, in their touring models. The standard version of this motor is 107 cubic inches with a 4.4 inch stroke and 3.9 inch bore. The CVO platform boasts 114 cubic inches from a 4.5 inch stroke and 4.0 inch bore. There is also a Screamin’ Eagle Stage 3 kit available to bump the motor up to 117 cubic inches.
Harley’s other Big Twin motor, the Twin Cam, operates using 1, two lobe cam per cylinder requiring a dual chain drive assembly. The Milwaukee Eight™ operates with a single, four lobe, cam driven by the flywheel pinion shaft with a single chain and hydraulic tensioner. I suspect a chain is used instead of more durable gears to reduce engine noise and to ease manufacturing tolerances by allowing more pinion shaft run out.
Like Harley’s previous motors, the Milwaukee Eight™ is a push rod driven, overhead valve motor. However, unlike any other standard production Harley, this bike has four valves and 2 spark plugs per head. These upgrades should make the motor much more powerful and efficient then the previous two valve, 1 plug heads. According to Harley-Davidson, these upgrades will increase air flow by 50% and the motor’s peak torque by 10% over the Twin Cam. To accommodate this increase in air flow the new motor utilizes a wider, higher flow air cleaner assembly.
In an effort to reduce vibration the motor’s are not only rubber mounted, but utilize a single internal counter balancer. This will be most noticeable at idle, where non-balanced rubber mounted Harleys vibrate the most. Rider and passenger comfort should also be improved by strategic oil passages designed to cool the hottest parts of the motor combined with a redesigned exhaust header.
The engine features a high output “G-Rotor” style oil pump that sits below the cam in the timing compartment. As with the Twin Cam motor it appears the cam chest will be the hub for oil feed and return throughout the engine.
The new power plant is offered with water cooled heads in the full dressed Ultra, Ultra Limited/Limited Low, Road Glide Ultra, and Ultra Trike models as well as the CVO Limited and CVO Street Glide. The remaining touring bikes utilize an air/oil cooled motor.
To read about the “Dual Cool” liquid and oil cooling systems of these bikes CLICK HERE.
To read about my initial road test and review of these bikes CLICK HERE.
There has been a lot of hype around these motors and I’m looking forward to getting one on the road as soon as possible!