It’s been about 17 years since Harley-Davidson debuted a new engine, an eternity in an industry where big engine changes typically happen once every five years. But Harley-Davidson is not your typical motorcycle manufacturer. And its customers are, well, a little different from the average. “Conservative” is a word often used to describe this demographic. Or put differently, Harley customers have extremely precise notions about what a Harley-Davidson should look, feel and sound like. A situation that sets impossibly tight boundaries when it comes to innovation and development. On the flipside, with so little pressure to change, the company must save a fortune on R&D spend.
The truth of the matter is that Harley-Davidson understands exactly what its customers want – more of the same – with the emphasis on “more” rather than “same”. Not novelty, and certainly not change for change’s sake.
“The guiding principle behind the Milwaukee-Eight engine was our voice of customer research from every region of the world,” explained Scott Miller, Harley-Davidson’s 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 [yet] also demanded we stay true to our legacy and respect the defining elements of a Harley Davidson V-Twin.”
In theory, the new Milwaukee-Eight engine, the ninth Big Twin design in the company’s history, is a clean-sheet design. Except you’d be forgiven for not being to tell the difference just by a glance. This all new engine that looks, feels and sounds a whole lot like the old one. Where the Harley customer is concerned, this should be a very good thing.
“While respecting the essential Big Twin character, we’ve created an all-new motor. Every aspect of performance, durability and styling has been improved,” said Alex Bozmoski, Harley-Davidson Chief Powertrain Engineer, who led the development team.
Matter of fact, Harley Davidson are so confident that they’ve delivered on their promise to deliver something totally new that remains true to legacy, they invited journalists from all over the world to Tacoma, Seattle to ride and experience these new bikes.
Let’s start with the basics. What’s changed in the engine? To answer that question, it might be better to start with what hasn’t changed. The engine retains the classic Harley-Davidson 45-degree V-Twin design. Apart from that, pretty much everything is new. The most pronounced difference between this ninth generation Harley Big Twin and its Twin Cam 88 predecessor introduced in 1999, is the new engine has a four-valve cylinder head (hence the Milwaukee-Eight moniker), single chain-driven cam, and dual spark plugs.
Capacity has been increased with the Milwaukee-Eight available in two engine sizes and three variations. The Milwaukee-Eight 107 (107 cubic inches/1,745cc) with oil-cooled cylinder heads, a Twin-Cooled Milwaukee-Eight 107 with liquid-cooled cylinder heads, and a Twin-Cooled Milwaukee-Eight 114 (114 cubic inches/1,870cc) featuring liquid-cooled cylinder heads.
Apart from increased displacement, the new engines have a higher compression ratio of 10:1, compared to 9.7:1 for the outgoing twin-cam. According to Harley-Davidson, the four-valve head improves intake and exhaust flow capacity by 50 percent while dual spark plugs per cylinder mean even more efficient combustion. The engine requires no valve adjustments as the valve train uses a rocker arm design that enables valve lash to be set at the factory for life. To reduce noise and friction and in the interest of mechanical simplicity, the engine uses a single chain-driven camshaft.
The rubber-mounted Milwaukee-Eight uses a new balance shaft that could have completely smoothened out the 45-degree V-twin’s vibration. The engineers decided against that, opting instead to eliminate just 75 percent of the engine’s primary vibration at idle, leaving just enough good vibes to let riders know they’re still very much on a Harley. Those vibes smoothen out markedly once underway. In fact, at anything above idle all through to redline, the new motor is almost turbine smooth.
While the engine is understandably taking centre stage, the all-new Touring suspension plays a crucial yet understated role in how well the new bikes ride. Upfront is an all-new 49mm non-adjustable Showa Dual Bending Valve (SDBV) fork that promises the linear damping performance and lighter weight of a racing-style cartridge fork. At the back are new larger piston Showa emulsion rear shocks with a remote preload adjuster. Apart from the ease of single-knob adjustment, the unit offers up to 30 percent more preload adjustment than earlier standard Touring shocks. “Preload can now be adjusted to match the load of rider, passenger and gear without tools or an air pump,” added Paul James, Harley-Davidson’s Director of Motorcycle Product Planning. “Once set, the preload will not leak down or require further adjustment.”
The Milwaukee-Eight engine is also equipped with a charging system that delivers 50 percent more output to the battery at idle to better support accessory lighting, audio, and other electrical accessories.
On the road
Over the next two days, Harley-Davidson have laid out a test route of some 700-plus kilometres along the coast and over the mountains of the Pacific Northwest. The time will give us the chance to sample the full range of Harley’s touring rigs – from basic Road King to full-spec Custom Vehicle Operations (CVO) Limited. Standing in the parking lot, it’s hard to pick one among the acres of lustrous chrome and deliberate over-engineering – all the bikes just ooze quality. Nothing looks cheap or flimsy.
Eventually settling into a Road King, a press of the starter sees the engine fire up with that distinctive roar that quickly settles into that familiar “potato-potato-potato” exhaust note. The engine, in comparison, is whisper quiet. A benefit, say Harley-Davidson, of lighter valves, a single cam, and improved driveline components. These changes have allowed engineers to virtually eliminate mechanical powertrain noise.
What hasn’t been eliminated is that agricultural clunk that lets you know you with absolute certainty that you are now in first gear. The clutch still requires some muscle to engage even though all Milwaukee-Eight powered models are fitted with new clutches that improve hydraulic actuation and reduce clutch lever effort by seven percent. Operating that clutch in traffic, as I would discover later, will seriously work my pathetic wrists and forearms.
For now, it doesn’t register. Everything is quickly forgotten once we get going. This is one seriously comfy ride. Even at speeds of up to 150 km/h, that engine is sooooooo smooth. You could comfortably ride at that speed all day and neither man nor machine would feel worse off. For a motorcycle that weighs in at 375 kg fully fuelled, the Milwaukee-Eight-fitted Road King is easy to manoeuvre and feels almost nimble. Thanks to a slimmer primary drive cover and lower-profile air cleaner cover, shorter riders will also find it easier to flat-foot the bike. About the only time you really feel the weight is when you need to park it. Then you feel every kilo.
In case you’re wondering, the Milwaukee-Eight engine doesn’t weigh any more than the engine it replaces. In fact, they weigh the same, according to Harley Davidson although no specific figures were provided. This does means the new engine’s extra torque and power should translate directly to better performance. Harley-Davidson say the Milwaukee-Eight engine produces approximately 10 percent more torque than the engine it replaces. While Harley does not provide official horsepower figures, data from the US Environmental Protection Agency (EPA) reveal the 107 produces about 93 hp at 5,020 rpm while the 114 generates 110 hp at 5.020 rpm.
It has been a couple of years since I was last on a Road King but this new one does feel significantly quicker. Harley-Davidson say the Milwaukee-Eight 107 accelerates 11 percent quicker from 0-100 kmh, equal to a two to three bike length improvement, and 11 percent quicker from 100-130 kmh in top gear, equal to a one to two bike length improvement, compared to the Twin Cam High Output 103.
“The Milwaukee-Eight engine,” explained Alex Bozmoski, “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.”
A three-bike-length difference between old and new sounds entirely plausible. During the ride, there was always plenty of instant power available for overtakes. And this difference in performance is likely to be magnified the moment the road turns curvy. Road bumps don’t unsettle the new bike as much and the more plaint suspension allows you to brake a little later and turn a little more aggressively. Over rough tarmac and around tight corners, the bike always felt planted. It was more than fast enough for the roads we were on. And unbelievably comfortable. This new engine and that all-new suspension make 400-kilometre days a walk in the park.
Heat of the moment
Big air-cooled twins generate a lot of heat. To address this, Harley-Davidson dropped the Milwaukee-Eight’s idle speed to 850 rpm from 1,000 rpm. The rear exhaust pipe was also rerouted so that it runs closer to the engine, and away from your legs. This seems to work put nicely for the oil-cooled engines. Many times during this cold and often wet ride, I’d keep repositioning legs and hands closer to the engine for warmth. On the twin-cooled bikes though, like the 114-mounted CVO Street Glide, warm air seems to flow precisely where it was needed. This is because the twin-cooled system uses radiators positioned within the lower fairing, just in front of your legs, keeping them toasty and comfy when its 10 degrees Celsius. That constant stream of warm air may not be so pleasant when its 35 degrees.
Single or Twin Cooled
The 107ci (1,750cc) oil-cooled engine will be used on models without fairing lowers, such as the Street Glide, Road Glide, Electric Glide Ultra Classic, and Road King. The 107ci twin-cooled version will power models with fairing lowers such as the Ultra Limited and Road Glide Ultra. The bigger 114ci (1,870cc) twin-cooled version will go into the CVO Limited and CVO Street Glide.