Motormouth: Harley-Davidson’s Milwaukee-Eight engine

New beginnings: Harley-Davidson’s Milwaukee-Eight engine

Did you feel it? Was that a MMS 6.0 earthquake centred on Milwaukee that you felt on August 23rd? Or was it the titanic rumble of ten thousand Hawgs hammering their split-beat thunder down the trans-Wisconsin I-43?

MY17 Key Feature. Touring Road King FLHR

MY17 Key Feature. Touring Road King FLHR

Neither of the above – it was bigger, actually – the long-awaited announcement from Harley-Davidson Motor Company of its new Milwaukee-Eight engine. The company’s first new motor in 15 years and the first four-valve-per-cylinder mill in the Marque’s 113-year history, it was truly epic.
The basic layout remains. It is still a 45-degree V-twin; its pistons sharing a common crank pin, with valves actuated by pushrods and driven by a single chain-driven camshaft. The differences are in its new slimmer outline and its more muscular output. What has not changed is the beat.
It is said to deliver more power, quicker throttle response, purer sound, better fuel economy, a smoother ride and more of that Harley-Davidson motorcycle feeling. Other advances include improved thermal comfort for rider and passenger thanks to reduced heat absorption, better heat rejection and a redesigned exhaust system. Targeted flow of coolant, oil or liquid, around the hottest areas of the cylinder heads, improves cooling.
New knock sensors enable precise timing control while the rear exhaust pipe is re-positioned and the catalyst relocated, to divert heat from the passenger. Idle speed is lowered from 1,000- to 850 rpm.

The engine will be made available in two sizes: 107 CID (1745 cc), oil- or liquid-cooled and 114 CID (1870 cc) that will be liquid-cooled only.
Each engine produces up to 11 percent more torque than the one it replaces. Apart from increased displacement, Milwaukee-Eights feature higher compression ratios and four-valve cylinder heads that improve intake and exhaust flow capacities by as much as 50 percent.
Dual spark plugs provide more efficient combustion and valve trains should never need adjusting, as the newly designed rocker arms enable valve lash to be factory-set for life. Its single chain-driven camshaft is lighter, mechanically less complex and creates less friction and noise.
“The Milwaukee-Eight engine retains our classic 45-degree V-Twin design,” said development team leader Alex Bozmoski, Harley-Davidson’s Chief Engineer, Power Trains. “It also retains Harley-Davidson’s legendary Big Twin power characteristic; strong low-end torque and a broad, flat power curve through the mid-range that’s ideal for Touring motorcycle riders.”
A new, slimmer primary drive cover and low-profile air cleaner improve rider legroom around the engine and enable easier reach to the ground. Assist and Slip clutches with stronger hydraulic actuation reduce lever effort by seven percent. The rubber-mounted engine features a single internal counter-balancer to eliminate 75 percent of primary vibration at idle – for more refined feel and greater comfort.
Lighter valves, the single camshaft, optimised cover designs and improved driveline components reduce mechanical powertrain noise. The engine intake and cleaner are designed to reduce noise while ensuring maximum airflow. As a result, the new engine is mechanically quieter with a richer exhaust tone. It meets all global noise and emissions standards while allowing the unmistakable rumble of its exhaust note to resonate triumphantly.

Text by Gordon Hall: Pics by Harley-Davidson.