The Milwaukee-eight family: an overview of Harley big twins

The Milwaukee-Eight

Today we want to offer you an overview of the latest big-twins produced by HD, also called the Milwaukee-eight (M8) family. The Harley-Davidson Milwaukee-Eight engine is the ninth generation of “big twin” engines developed by the company. But only Harley’s third all-new Big Twin in 80 years. First introduced in 2016, these engines differ from the traditional Harley Big Twin engines in that there are four valves per cylinder, totaling eight valves, hence the name.

Although at first glance the outward appearance is quite similar to its Twin-Cam predecessor, the truth is that this new propeller has been completely designed from the beginning, improving the strengths of the previous models and correcting the shortcomings produced by the incessant increases. of displacement and power of recent times. Let’s review the main changes.


The Milwaukee-Eight performance

Milwaukee-Eight cylinder
Milwaukee-Eight cylinder

The engine offers more torque and power than its predecessors and maintains the 45º angle between the cylinders. The M8 has 11% more torque, which together with the larger displacement provides remarkably high power and performance. Moreover it weights like its predecessor and with this power increase, acceleration is 11% higher than that of the Twin-Cam.

Clearly, the increases in displacement and torque must be accompanied by a reinforced lowered engine. The crankshaft has been oversized and the bearings can support a greater load. The new base is 23% more resistant than the previous one and still weighs the same. This was possible because the unnecessary material was removed, giving the appearance that the covers now “embrace” the internal parts, following their shape.


The new concept of comfort


A new, finer, primary transmission cover and the lowered profile of the air filter cover improve the pilot’s legroom around the engine, facilitating the access of many drivers to the ground. All models with the Milwaukee-Eight engine have an improved “Assist and Slip” hydraulic clutch transmission, which reduces lever effort by 7%.

For the first time the engine mounts a balancing countershaft inside the engine attached to the frame by silentblock. It consists of a mass that rotates in the opposite direction to the motor shaft, absorbing most of the vibrations emitted by it. This means an unprecedented smoothness without losing “character”.

The design team presented also a completely new suspension system that allows preload adjustment up to 30% higher than the previous ones quickly and easily. The front suspension has a new “Showa dual-bending valve” suspension technology with the damping performance of a competition cartridge fork, with more linear behavior and less weight. Basically this means that the fork adapts its hardness and its operation in real-time, “detecting” the changes in the stability of the ground or in the running speed.


M8 efficiency

Head of the Milwaukee-Eight
Head of the Milwaukee-Eight

Thanks to the use of double spark plugs per cylinder, optimized ignition and high flow heads with 4 valves per cylinder, engine efficiency is improved, reducing fuel consumption.

The new M8 has also a better temperature management. With the new design it was possible to keep the heat inside the engine (which is where it should be) by reducing the temperature absorption of the cylinders and the heads, aided by the cooling (of oil or water) in the points warmer than them. Both the oil pump and the water pump have been redesigned to move a higher volume per minute, and now the idle speeds have been lowered from 1000 rpm to 850 rpm.

As if not enough, it has an improved electric charge. modern motorcycles have more and more electrical and electronic devices (engine management, audio and multimedia, heating, lights …), therefore a new alternator has been installed that provides 50% more power with the engine to a minimum in order to meet these and future electrical needs.


The M8 look and sound


The engineers wanted to respond to the aesthetic needs of the most loyal customers and gave the M8 a “muscular” appearance, wrapping the mechanical parts in a more direct way, as if it were a mechanical skin, making us understand the components that they hide under the covers. The surface of the cooling fins has also been increased, providing functionality and creating a more massive appearance.

Moreover many of the changes in the engine have been aimed at minimizing the sounds inside the engine to increase the sound of the exhaust in compliance with noise emission regulations. As was said when the Evolution engine “We reduce noise to increase music” was introduced.

The M8 107
The M8 107

The Milwaukee-Eight family


Here the list of M8 harley is currently producing:

– Milwaukee-Eight 107 (1745 cc) TORQUE max 145 Nm at 3.000 rpm HORSEPOWER 86 HP / x64 Kw at 5020 rpm.

The little version of the family. Harley produces it in both air and twin-cooled variants. It currently equips the Tourings and the Softails.

– Milwaukee-Eight 114 (1,870 cc) TORQUE max 160 Nm at 3.500 rpm HORSEPOWER 90 HP / x67 Kw at 4500 rpm.

The strong version of the family. It is only available in the air-cooled variant. This because the Twin-cooled that used to equip the CVOs was replaced by the 117. At the moment it equips some Softail models.

– Milwaukee-Eight 117 (1,920 cc) TORQUE max 166 Nm at 3,500 rpm HORSEPOWER 106 HP / x78 Kw at 5450 rpm.

The steroid variant of the range. Harley produces it in the Twin-cooled variant only. It equip the most extreme Harley CVOs.

– Milwaukee-Eight 131 (2.147 cc) TORQUE max 177 Nm HORSEPOWER 121 HP

The new, the biggest and the most powerful engine ever. Harley introduced it for the first time in January. At the moment it can equip all the Tourings since 2017 paying an overcharge.


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