At last – is this the Harley engine that won’t burn your legs, shake your teeth out and leave you last at the lights?Well, not quite, especially where power comparisons with competitive offerings (Indian Motorcycle aside) are concerned. But that hasn’t stopped Harley from boasting that the “all-new ‘Milwaukee-Eight’ engine delivers more power and an improved motorcycling experience for riders and passengers while retaining the iconic look, sound and feel of its predecessors.”
True, it is a mostly all-new design, certainly as far as the heads are concerned. The Milwaukee-Eight engine is said to offer “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.”
In other words, is Harley accepting that previous engines offer poor throttle response, poor power in real-world traffic conditions, way too much noise and way too much in the way of vibrations?
It kind of sounds like that from their press release, and note the detail of their remarks here – “more of the feeling riders want from a Harley-Davidson Touring motorcycle engine.”
One line of speculation suggests that in a parallel to what happened with the two-stage introduction of the Twin Cam in 1999/2000, there is likely to be a ‘B’ version of the ‘Eight’ next year for the cruisers – or in a new mid-cycle cruiser-esque launch or launches.
However, are Harley quite clearly signalling here that, in fact, the ‘Milwaukee-Eight’ is destined to be a tourer engine “only”?
In which case, will the cruisers be allowed to trade on the Rushmore hype of the Twin-Cooled motor for some years to come, or (could we be this lucky?) is there in fact another big step in refreshment and refinement of the offer to come with, whisper it softly, another engine platform also about to emerge at some stage in the next six to 24 months?
Either way, the new ‘Milwaukee-Eight’ engines will power every 2017 Harley-Davidson Touring and Trike motorcycle model. They will be offered in two displacements and three variations.
The 107-inch version (1750cc) features 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.
Based on the existing cooling technology introduced with the Rushmore tourers, a Twin-Cooled 107 incher (107 CID, 1750cc) features liquid-cooled cylinder heads for the Ultra Limited/Ultra Limited Low, Road Glide Ultra and Tri Glide Ultra models.
Then a Twin-Cooled ‘Milwaukee-Eight’ 114-incher(1870cc) featuring liquid-cooled cylinder heads will power the CVO Limited and CVO Street Glide models.
The new engine is said to produce 10 percent more torque than the engine it replaces in Touring models. In addition to increased displacement, it 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.
Weighing the same as the lower-powered engine it replaces, the power-to-weight ratio of the ‘Eight’ is one of the significant factors in delivering increased power - there can be no doubt that even as you read this, the aftermarket will be busy working on lighter weight, higher strength components to push that ratio way further.
The 107-inch version of the ‘Eight’ is said to accelerate 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 114-inch version is said to accelerate 8 percent quicker 0-60mph, and 12 percent quicker 60-80mph than the Twin Cam 110.
Heat has always been a big issue for Harley. The ‘Eight’ is described as offering “improved rider and passenger thermal comfort due to reduced heat absorption, increased heat rejection and a redesigned exhaust system. A precision cooling strategy [has been developed] 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. The rear exhaust pipe is repositioned and the exhaust catalyst is relocated to move heat away from the passenger. Idle speed is lowered from 1,000 rpm to 850 rpm.”
Rider comfort is also enhanced by the new, slimmer primary drive cover, and the low-profile shape of the (less than aesthetically nourishing) air cleaner cover, providing 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 rubber-mounted engine features a single internal counter balancer that is said to cancel 75 percent of primary vibration at idle “for a more refined feel and more comfortable experience for rider and passengers while retaining the classic character of Harley V-twin engines.”
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 engine is mechanically quieter, “enabling a richer exhaust tone, meeting all global noise and emissions standards, while allowing the unmistakable rumble of its exhaust note to resonate.”
The 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.”
Brad Richards, Harley-Davidson’s Director of Styling, is quoted as saying: “The ‘Milwaukee-Eight’ engine is styled to project power. I compare it to the back of a swimmer, lean in the waist but broad and muscular in the shoulders.
“The rocker covers look like skin stretched taut over muscle, like the rocker arms are about to burst out of the engine. 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.”