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Harley-Davidson unleashes more powerful and efficient Milwaukee-Eight engine

Harley-Davidson unveiled its first new motorcycle engine in over 15 years, a completely new, single cam engine to replace the Twin Cam engine that debuted in 1999.

It was time for an update. Harley-Davidson's engineering and marketing teams heard from nearly 1,000 riders and expected buyers from around the world on their wish list for the next generation Harley engine.

It reads like a multiple choice exam:

  • More power. 
  • Cooler ride. 
  • A machine that fits me physically. 
  • The classic look, but different enough to stand out.
What Harley-Davidson riders will be getting is all of the above — and then some.

"It was like operating on the pope," said Alex Bozmoski, new product chief engineer. "Everyone wants to give advice to make sure it is done right."

The all-new Harley-Davidson Milwaukee-Eight engine, ninth in the lineage of the company's Big Twin engines, delivers more power and an improved motorcycling experience for riders and passengers while retaining the iconic look, sound and feel.

"The Milwaukee-Eight engine retains the classic Harley-Davidson 45-degree V-Twin design," said Bozmoski. "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 midrange that's ideal for the touring motorcycle rider."

The Milwaukee-Eight engine offers quicker throttle response, more passing power, purer sound, better fuel economy, a smoother ride.

I was one of the lucky four journalists to test out the new drivetrain before Harley revealed it to dealers at their annual meeting in Boston on Tuesday.

After putting a bevy of bikes through their paces at Blackhawk Farms Raceway, I can say that the machines exceeded my expectations.

The Milwaukee-Eight has one less cam, but twice as many valves — two intake valves and two exhaust valves per cylinder. That is eight valves, hence the new moniker.

The new engine initially will be installed only on the touring motorcycles including the Street Glide, Road Glide, Electra Glide, Road King and Tri Glide models. No date has been announced for it to be installed on the remaining product line, but that day will surely come.

More power comes from the larger displacement, four-valve heads and higher compression ratio. It produces 10 percent more torque than the former TC engine.


Increased torque results in quicker acceleration.

The standard engine's displacement is 107 cubic inches (1,750 cc). The CVO (custom vehicle operations) version's displacement is 114 cubic inches (1,870 cc) The 107 accelerates 11 percent quicker to 60 mph, equal to a two to three bike length improvement. It is 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.

Having ridden two hours on a TC 110 motorcycle from Milwaukee to the Blackhawk Farms Raceway, I could definitely feel the difference in torque on the road and from a standing start to over 60 mph on the front straight.

Keeping with Harley tradition, the engines are basically air-cooled, but some feature precision oil-cooled heads.

The 107 CID engine has 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.

The twin-cooled 107 engine has liquid-cooled cylinder heads for the Ultra Limited/Ultra Limited Low, Road Glide Ultra and Tri Glide Ultra models.

The twin cooled 114 CID engine has liquid-cooled cylinder heads for the CVO Limited and CVO Street Glide models.

Despite the larger displacement and increased compression, the new engine gets better fuel economy yet produces 10 percent more torque than the engine it replaces in touring models. The improvement comes from 50 percent better intake and exhaust flow thanks to four valves per cylinder. To supply the necessary air, there is a high flow air filter as well as a bigger throttle body with a 55 mm diameter. A new knock sensor for each cylinder enables precise ignition timing control.

Not only are there twice the number of valves, there are twice the number of spark plugs — two per cylinder. New Bosch fuel injectors have a dual spray pattern directed at each of the two intake valves.

The only items that I noticed as carry-overs from the previous engine were the oil filter and drain plug. The oil capacity increases from 4.5 to 5.0 quarts and oil is strategically used to help cool the engine.

Although the new engine is the star of the show, improvements to riding comfort are the supporting actors.

Anyone who has ridden a Harley in stop-and-go traffic will agree that roast leg of rider was on the menu. The proximity of the exhaust pipe (which also housed the catalytic convert) to the right leg was an issue.

A cooler ride results from improved exhaust pipe routing and relocating the catalytic converter.

The exhaust header pipe from the rear jug turns down abruptly from the cylinder head, keeping it away from the rider's right thigh. The catalytic converter was moved to the rear, away from the rider's knee where it had been. Liquid-cooled heads also dissipate some of the heat.

The idle speed was lowered from 1,000 rpm to 850 rpm while also reducing heat and noise. Yet changes to the charging system provide a 50 percent improvement in output — 24 amps at idle and 30 amps above 1,050 rpm. The number of power accessories on modern motorcycles keeps growing.

The rubber-mounted engine features a single internal counterbalancer (vibration damper) that cancels 75 percent of primary vibration at idle for a more refined feel and more comfortable ride. In fact, it did such a good job that the engineers had to adjust the vibration control down from 100 percent to 75 percent, just so Harley owners will still feel that familiar motion.

None of these changes hurt the iconic Harley-Davidson exhaust note. Less mechanical noise from the engine, due in part to lighter valves, has actually enhanced the rumble for the rider.

Power without control is crude.The air cleaner housing is more ergonomic and the bulge on the primary drive cover (aka "derby cover") is slimmed down. Yet the new nine-plate, slipper clutch behind the cover is stronger.

The front forks are equipped with Showa dual-bending valve technology dampers providing a smooth ride and control confidence.

The Showa emulsion rear shocks feature an adjustment knob — no tools or inflation adjustments — and up to 30 percent more pre-load range (40 pounds) for extra carrying capacity.

The Milwaukee-Eight just might be a 10.

Source : www.chicagotribune.com

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