Harley's Milwaukee-Eight Engine - Everything You Need To Know

The whirlwind of motorcycle revelations from the unveiling of Harley-Davidson’s new powerhouse left many riders with as many questions as there was excitement. Always here to help, Clutch and Chrome has a closer look at the new Milwaukee-Eight engine.

There are plenty of questions around what the Milwaukee-Eight engine is and where it fits in the new models. Before we answer these questions, a quick look at what brought us to yesterday’s remarkable news.

Whether a fan of Harley-Davidson or not, Tuesday August 23rd was a big day in the world of motorcycles. The all-new Harley-Davidson Milwaukee-Eight engine is only the ninth in the lineage of the company’s iconic Big Twin engines. Aside from continuing to make the American motorcycle manufacturer competitive, the new engine is a bold move by Harley. Many of their die-hard riders are traditionalists, making any changes to any part of a Harley-Davidson a challenge and the V-Twin is high on that list.

This demand of staying true to what riders feel a Harley-Davidson ‘is’ was seen in a statement from the manufacturer when describing how the new engine came about.

“The guiding principle behind the Milwaukee-Eight engine was our voice of customer research from every region of the world,” said Scott Miller, Harley-Davidson Vice-President of Styling and Product Development Strategy. “Riders asked us to create a new engine designed to enhance their motorcycle touring experience in every way. Those same voices also demanded that we stay true to our legacy and respect the defining elements of a Harley-Davidson V-Twin. It was a big challenge, but one we’ve met. With the Milwaukee-Eight, a new era of Harley-Davidson power, performance and innovation has been forged.”

As dedicated as Harley may be to their hardcore fans, attracting new riders to the brand is something the motorcycle manufacturer needs to do, not just to be successful but according to many financial experts, it’s needed for the company’s very survival.

With this in mind, it was refreshing to see some obvious non-Harley types tuning and posting comments during the manufacturer’s live Facebook event Tuesday afternoon. During the special live presentation of not only the new engine but other announced advancements and where they’ll fit in the 2017 line-up, many questions were asked about what the Milwaukee-Eight engine is and which models will enjoy it.

An all-new design, the Milwaukee-Eight engine promises quicker throttle response, more passing power, purer sound, a smoother ride and more of the feeling riders want from a Harley-Davidson Touring motorcycle engine.

While delivering more power and an improved motorcycling experience for riders, according to Harley-Davidson ‘the Milwaukee-Eight engine retains the iconic look, sound and feel of its predecessors,’ again showing the fine line the famous company must walk.

Answering the overwhelming question of which models the new engine will power, we can also detail the different versions of the Milwaukee-Eight engine. Milwaukee-Eight engines will be offered in two displacements and three variations, so grab a piece of paper to follow along;

Milwaukee-Eight 107 (107 CID, 1750cc) featuring precision oil-cooled cylinder heads for the Street Glide/Street Glide Special, Road Glide/Road Glide Special, Electra Glide Ultra Classic, Road King and Freewheeler models.

Twin-Cooled Milwaukee-Eight 107 (107 CID, 1750cc) featuring liquid-cooled cylinder heads for the Ultra Limited/Ultra Limited Low, Road Glide Ultra and Tri Glide Ultra models.

And the most powerful version, Twin-Cooled Milwaukee-Eight 114 (114 CID,1870cc) featuring liquid-cooled cylinder heads is not surprisingly found on Harley’s premium motorcycles, the CVO Limited and CVO Street Glide models.

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Three 2017 models enjoying versions  of the new Milwaukee-Eight engine
Street Glide, Ultra Limited Low and CVO Limited - Source Harley-Davidson

More Power

Each Milwaukee-Eight engine produces 10 percent more torque than the engine it replaces in Touring models. In addition to increased displacement, the Milwaukee-Eight engine features a higher compression ratio and four-valve cylinder heads with 50 percent more intake and exhaust flow capacity.

The valve train requires no adjustment as the design of the rocker arms enables valve lash to be set at the factory for life. Dual spark plugs for each cylinder contribute to more-efficient combustion. A single chain-driven camshaft is lighter, mechanically less complex and creates less friction and noise.

“The Milwaukee-Eight engine retains the classic Harley-Davidson 45-degree V-Twin design,” said Alex Bozmoski, Harley-Davidson Chief Powertrain Engineer, who led the development team. “It also retains the power characteristic that is the real legacy of the Harley-Davidson Big Twin: strong low-end torque with a broad, flat power curve through the mid-range that’s ideal for the Touring motorcycle rider.”

Quicker Acceleration

The Milwaukee-Eight engine weighs the same as the engines it replaces, so all of its extra power contributes directly to improved acceleration performance over the different versions.

The Milwaukee-Eight 107 accelerates 11 percent quicker 0-60 mph, equal to a two to three bike length improvement, and 11 percent quicker from 60-80 mph in top gear, equal to a one to two bike length improvement, compared to the Twin Cam High Output 103.

The Milwaukee-Eight 114 accelerates 8 percent quicker 0-60 and 12 percent quicker 60-80 than the Twin Cam 110.

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Usually more performance means more heat but according to Harley-Davidson, this isn’t the case with the new powerhouse. The Milwaukee-Eight engine offers improved rider and passenger thermal comfort due to reduced heat absorption, increased heat rejection and a redesigned exhaust system.

Each Milwaukee-Eight engine features a precision cooling strategy based on the specific demands of the motorcycle model, using a targeted flow of either oil or liquid coolant around the hottest areas of the cylinder heads. A new knock sensor for each cylinder enables more-precise timing control.

Looking to overall design, the rear exhaust pipe is re-positioned and the exhaust catalyst is relocated to move heat away from the passenger. Finally, idle speed is lowered from 1,000 rpm to 850 rpm allowing the engine to run cooler at a standstill.

Part of attracting riders new to the brand as well as those fresh to the past time of motorcycles is to build less overwhelming models. While big was beautiful some years ago, the latest trends have riders wanting a motorcycle that looks and feels manageable, easy to control and fun to ride.

A new, slimmer primary drive cover and the low-profile shape of the air cleaner cover provide improved rider legroom around the engine and an easier reach to the ground for many riders. All Milwaukee-Eight powered models are fitted with an Assist and Slip Clutch with improved hydraulic actuation that reduces clutch lever effort by 7 percent.

The Milwaukee-Eight engine features sleek, modern styling that respects the heritage of previous Harley-Davidson Big Twin engines.

“The Milwaukee-Eight engine is styled to project power,” said Brad Richards, Harley-Davidson Director of Styling. “I compare it to the back of a swimmer, lean in the waist but broad and muscular in the shoulders.”

Adding to ‘fun factor’, the rubber-mounted Milwaukee-Eight engine features a single internal counter balancer that cancels 75 percent of primary vibration at idle for a more-refined feel and more-comfortable experience for rider and passengers. However, the company is quick to note the new engine retains the classic character of Harley V-Twin engines.

It appears the design team wanted to recall the powerful engines of Harley’s past, most notable the famous Knucklehead.

“The rocker covers look like skin stretched taut over muscle, like the rocker arms are about to burst out of the engine,” said Richards. “For the first time since the Knucklehead, the rocker covers reflect the action going on below. And they are massive. When you sit on the bike you can look down and see more of this engine.”

Whenever Harley-Davidson touches anything on its motorcycles, one of the first questions from riders is ‘Will it sound like a Harley-Davidson?’ Probably the most famous signature of the legendary brand, capturing the sound their motorcycles are known for could be considered the biggest challenge for the design and engineering teams.

They feel this new line of engines does in fact manage that, offering a richer exhaust note.

Harley-Davidson notes the first step to finding the sound was to reduce all the other noise coming from the motorcycle. Lighter valves, a single camshaft, optimized cover designs and improved driveline components eliminate mechanical powertrain noise. The engine intake and air cleaner are designed to reduce intake sound while ensuring maximum air flow. As a result, the new Milwaukee-Eight engine is mechanically quieter, enabling a richer exhaust tone, and meets all global noise and emissions standards while allowing the unmistakable rumble of its exhaust note to resonate.

Simply put, a quieter motorcycle requires a quieter, but richer sound leaving bikers happy and all those around them in traffic happier.

Finally, today’s motorcycle is beyond the basic rides that popularized the riding past time all those generations of bikers ago. While this article is focused on the Milwaukee-Eight engine and not the modern accessories found on the different models, designers reportedly ensured the new powerhouse could feed everything found on the new line-up. The Milwaukee-Eight engine charging system delivers 50 percent more output to the battery at idle to better support the power demands of Touring riders, including accessory lighting, performance audio, and heated gear and other accessories.

If we’ve missed any of your questions about the new Milwaukee-Eight engine, let us know and we will get it answered. But at this point, interested riders need to leave the online videos and spec sheets behind, make their way to a dealership and test these new rides for themselves.

The proof as they say, is in the pudding. In this case, that pudding comes in 1750cc to 1870cc and has ‘HD’ stamped on it. Readers should remember however, they are test-riding a moment in motorcycle history.

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